Systems and methods for freezing samples

Abstract

Liquid drug formulations must be frozen as part of the lyophilization process to remove the solvent via sublimation. This freezing process is typically done through shelf-based cooling. The present disclosure provides, in various aspects, forced convection gas cooling chamber that can be used with a continuous lyophilizer to freeze product in vials or other containers without requiring solid contact between the vials or other containers and another surface. The gas temperature can also change rapidly, and the present disclosure relates in various aspects to the implementation of a thermal quench method for controlled nucleation.

Description

WGS Ref. M0925.71059WQ00MIT Ref. 26103SYSTEMS AND METHODS FOR FREEZING SAMPLESRELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63 / 703,132, filed on October 3, 2024, which is hereby incorporated by reference herein in its entirety.GOVERNMENT FUNDING

[0002] This invention was made with government support under U01 FD006755 awarded by the Food and Drug Administration. The government has certain rights in the invention.FIELD

[0003] The present disclosure relates, in various aspects, to pharmaceutical lyophilization of liquid medicines to form dry powder form for later reconstitution.BACKGROUND

[0004] The freezing stage of lyophilization can limit the overall process's speed and reliability. Variation in the freezing stage can create variations of as much as 25% in the time spent on lyophilization. This variation in process time can lead to large inefficiencies within a system, where some vials finish sublimating much sooner than others. If these vials are grouped together, either on a shelf on large batch lyophilizers or on a smaller tray as used in the system described in this document, then those groups will have to wait for the slowest drying vials before they can exit the system.

[0005] The freezing process also affects product cake stability during drying. During the freezing process, the product is separated from most of the water, as the water freezing into ice crystals causes the product to concentrate into its cake structure. This separation allows the ice crystals to sublimate when exposed to a vacuum, removing most of the water from the system. These ice crystals may also determine the cake structure, as it is formed around the crystallized water. Structural differences in the cake can lead to the variance in drying times, e.g., because without wishing to be bound by any particular theory, in some embodiments the relative sizes of1#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 residual pores left behind after sublimation can affect the cake’s resistance to mass transfer during sublimation.

[0006] Most freezing in commercial lyophilization is done through shelf temperature control. The vials rest on thermally conductive shelves which follow prescribed cooling profiles, which are typically temperature ramps and holds. However, shelf-based cooling systems may not be compatible with a continuous lyophilizer, as the vials need to move through the system. This motion of the vials through a continuous lyophilizer requires separating the vials from the shelf or the shelf from the machine, and this separation disrupts the connections required for conductive cooling.

[0007] An alternative, rapid form of freezing is quench freezing using a cold liquid, such as liquid nitrogen. The vials containing the product are partially submerged in the cold material, rapidly freezing the sample. This method freezes the product very quickly, but it also tends to freeze vials heterogeneously. This heterogeneity is likely related to the uncontrolled nucleation that occurs during this rapid freezing process. While this freezing method would significantly reduce the freezing time relative to traditional lyophilizers, it does not provide the necessary freezing uniformity required to ensure consistent product quality.

[0008] Another freezing method is known as spin freezing. This method involves rotating the vial at a high speed so that centrifugal forces cause the fluid to spread out and coat the entire interior surface of the vial with a thin film. The spinning vial is then exposed to a cooling environment, such as a cold gas jet, freezing the film inside the vial. Spin freezing requires individualized actuation for each vial to do the spinning, which adds significant complexity to the system. Additionally, it notably alters the cake structure from what traditional lyophilizers produce. This different cake structure could affect the product’s reconstitution, as the material is frozen under significant loads created during the spinning process. Thus, spin freezing is not a sufficient methodology for general use in continuous lyophilizers.SUMMARY

[0009] In one aspect, a lyophilization freezing module is provided. According to some embodiments, the lyophilization module comprises: a housing including an internal chamber and a base configured to be disposed on a supporting surface; a passage extending through the housing with a first opening and a second opening configured to permit movement of a2#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 lyophilization tray through the passage; a first plurality of fluid flow inlets positioned on a first side of the internal chamber; a second plurality of fluid flow inlets positioned on a second side of the internal chamber opposite from the first side; one or more fluid flow outlets fluidly coupled to internal chamber, the first plurality of fluid flow inlets, and the second plurality of fluid flow inlets; one or more fluid flow actuators configured to create a flow of fluid from the internal chamber through the one or more outlets, through one or more flow passages, and back into the internal chamber through the first plurality of fluid flow inlets and the second plurality of fluid flow inlets; and one or more baffles extending from an upper portion of the internal chamber towards a lower portion of the internal chamber, wherein the one or more baffles are configured to prevent direct flow from the first plurality of fluid flow inlets and the second plurality of fluid flow inlets to the one or more outlets.

[0010] In another aspect, a method for freezing a material during a lyophilization process is provided. According to some embodiments, the method comprises: flowing a cooling fluid from a first plurality of fluid flow inlets across a lyophilization tray in a first direction towards a lower opening disposed between one or more baffles extending from an upper portion of an internal chamber the lyophilization tray is disposed in towards a lower portion of the internal chamber; flowing the cooling fluid from a second plurality of fluid flow inlets across the lyophilization tray in a second direction towards the lower opening; directing the cooling fluid towards one or more fluid flow outlets with the one or more baffles; and flowing the cooling fluid from the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

[0011] In yet another aspect, a lyophilization freezing module is provided. According to some embodiments, the lyophilization module comprises: a housing including an internal chamber and a base configured to be disposed on a supporting surface; one or more first fluid flow inlets in fluid communication with the internal chamber; one or more fluid flow outlets fluidly coupled to the internal chamber; a diffuser fluidly coupled to the one or more fluid flow outlets; a first recirculation duct fluidly coupling the diffuser to the one or more fluid flow outlets; and one or more fluid flow actuators configured to create a flow of fluid from the internal chamber through the one or more outlets, through the diffuser, and back into the internal chamber through the one or more fluid flow inlets.3#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0012] It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures.

[0013] In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control. If two or more documents incorporated by reference include conflicting and / or inconsistent disclosure with respect to each other, then the document having the later effective date shall control.BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0015] FIG. 1 provides a schematic, side-view illustration of fluid flow through a nonlimiting lyophilization freezing module chamber, according to some embodiments.

[0016] FIGS. 2A-2B provide a non-limiting, schematic perspective illustration of a fluid recycling system, identifying various components of the recycling system (FIG. 2A) and illustrating fluid flow through the recycling system (FIG. 2B) according to some embodiments.

[0017] FIG. 3 provides a non-limiting schematic illustration of a manifold of a fluid recycling system, according to some embodiments.

[0018] FIG. 4 provides a schematic cross-sectional illustration of a non-limiting lyophilization freezing modules, according to some embodiments.

[0019] FIG. 5 provides a schematic representation of a non-limiting lyophilization freezing method, according to some embodiments.

[0020] FIG. 6. provides a schematic, top-view illustration of a non-limiting lyophilization system, according to some embodiments;

[0021] FIGS. 7A-7E illustrate simulated fluid velocity and maximum vial differential, according to some embodiments.4#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0022] FIGS. 8A-8B illustrate the results of fluid flow simulations based on positioning the gas inlet on the side of the vials (FIG. 8A) or above the vials (FIG. 8B), according to some embodiments. These simulations showed that the gas inlet positioned above the vials could offer improvements in cooling rate and uniformity. However, further simulations showed that increased gas speed led to the side inlets outperforming the top inlets.

[0023] FIG. 9 illustrates the results of varying gas speed on freezing time during exemplary simulations, according to some embodiments.

[0024] FIG. 10 illustrates the simulated effect of inlet height on freezing time, according to some embodiments.

[0025] FIGS. 11A-1 IB illustrate an exemplary comparison of unidirectional and bidirectional fluid flow over lyophilization vials, according to some embodiments.

[0026] FIGS. 12A-12B schematically illustrates the air temperature (FIG. 12 A) uniformity at the inlet and the air velocity (FIG. 12B) uniformity as a function of position within an exemplary chamber, according to some embodiments.

[0027] FIGS. 13A-13B illustrates the matching of the gas flow on opposite sides of an exemplary cooling chamber, according to some embodiments.

[0028] FIG. 14 illustrates an exemplary setup for measuring temperature in lyophilization samples using thermocouples, according to some embodiments.

[0029] FIG. 15 illustrates the temperature of air and vials during an exemplary freezing test, according to some embodiments.

[0030] FIGS. 16A-16B illustrate the results of nucleation using thermal quenching, according to some embodiments.

[0031] FIG. 17 provides an exemplary comparison of set temperature and actual temperature at a variety of gas flow rates controlled by a cascade controller, demonstrating that the cascade controller successfully controlled the system, according to some embodiments.DETAILED DESCRIPTION

[0032] Efficient lyophilization processes benefit from homogeneous cooling conditions that standardize the cooling of samples for lyophilization. Forced convection of fluid (e.g., gas flow) is an economical way to freeze samples, but can result in inhomogeneous cooling that limits the overall rate of lyophilization. For example, in some embodiments, the overall rate of5#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 lyophilization is reduced because drying must be delayed until the slowest-to-freeze samples are frozen) and / or sample standardization. Moreover the inhomogeneous cooling may reduce sample standardization. For example, non-uniform freezing temperatures can result in different nucleation and growth rates for ice in different samples, and can thus result in different ice crystal sizes and ultimately in different structures for dried lyophilized products. These problems can increase process times and process costs, limiting the utility of convective cooling for lyophilization.

[0033] The present disclosure provides, in various embodiments, improvements to lyophilization methods and systems that improve the homogeneity of the temperature distribution produced during forced convection cooling of samples. In some aspects, the improvements relate to the recognition that unidirectional fluid flow (e.g., gas flow) produces inhomogeneous cooling (e.g., because samples closest to a cooling fluid inlet become colder than samples further from the cooling fluid inlet), and that multidirectional fluid flow can be used to produce more homogeneous temperature distributions.

[0034] Further, the disclosure relates to various improvements for controlling the directions of fluid flow during multidirectional convective cooling. In multidirectional cooling, without wishing to be bound by any particular theory, the meeting of various fluid flow fronts can tend to direct fluid flows away from samples and towards lower-pressure zones. Solutions provided for improved control of fluid flow can help to keep convection directed onto the samples, increasing the speed and efficiency of cooling, depending on the embodiment. As a specific example, in some embodiments the disclosure provides a system of one or more baffles configured to direct fluid flow towards samples for lyophilization. Exemplary baffles are described in greater detail below, and are schematized in various figures discussed in greater detail below.

[0035] In some aspects, the disclosure relates to a lyophilization freezing module comprising a fluid inlet, a fluid outlet, and one or more baffles. The lyophilization freezing module may be a complete lyophilization system, or may be a module configured for use in a larger lyophilization system (e.g., a lyophilization system that further comprises additional lyophilization freezing modules configured to operate serially or in parallel). In some embodiments, the lyophilization freezing module comprises more than one inlet. For example, the lyophilization freezing module may comprise a first inlet and a second inlet, and the first and6#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 second inlets maybe configured to provide multidirectional flow (e.g., by being positioned opposite one another such that fluid flow through the first inlet opposes fluid flow through the second inlet). Other configurations are also possible. The lyophilization freezing module may comprise a common outlet (e.g., such that fluid flow from one or more inlets is forced to leave the lyophilization freezing module via the same outlet) or a plurality of outlets, as the disclosure is not so limited.

[0036] According to some embodiments, the lyophilization freezing module comprises one or more baffles. A baffle may be configured to direct the flow of fluid (e.g., gas) through at least a portion of the lyophilization freezing module. For example, in some embodiments, the baffle is configured such that fluid flowing into the lyophilization freezing module through an inlet enters on a first side of the baffle and is substantially retained on the first side of the baffle before flowing to the outlet. As discussed in greater detail with reference to the figures described below, the baffle may be configured to direct fluid flow towards a position where samples are inserted into the lyophilization freezing module during operation of the lyophilization freezing module. For example, a baffle may be positioned above at least some lyophilization samples when the lyophilization samples are introduced to the lyophilization freezing module. One or more baffles may also be used to guide fluid flow from the sample to the outlet of the lyophilization freezing module, depending on the embodiment. Any appropriate number of baffles may be used, depending on the embodiment, as the disclosure is not so limited.

[0037] According to some embodiments, a lyophilization freezing module is used to flow a cooling fluid from a first plurality of fluid flow inlets across a lyophilization tray in a first direction. The lyophilization freezing module may further be used to flow a cooling fluid from a second plurality of fluid flow inlets across a lyophilization tray in a second direction (e.g., a second direction at least partially opposite from the first direction).

[0038] The chamber may comprise one or more outlets (e.g., at the top of the internal chamber), towards which the cooling fluids are flowed. Without wishing to be bound by any particular theory, a cooling fluid entering a lyophilization freezing module will tend to favor the paths of lower flow resistance extending from a corresponding fluid flow inlet where it enters the chamber to a fluid flow outlet where it can leave the chamber. Often, the least resistant path is the direct path from the inlet to the outlet. In the case of unidirectional fluid flow, straightforward arrangements of inlets and outlets can often be used to ensure that samples contact the fluid flow,7#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 according to some embodiments. For example, in unidirectional flow embodiments, a lyophilization tray can be placed directly between an inlet and an outlet, thereby placing the lyophilization tray in a direct path of fluid flow. But in the case of multidirectional convective cooling, cooling fluid flows enter the chamber in multiple directions and may flow directly towards the one or more corresponding outlets. This leads to non-uniformities in the flow of cooling gas, and thus temperatures, within the module. Correspondingly, the one or more, and in some instances plurality of, containers positioned in a lyophilization tray in the module may be subjected to different temperatures and cooling rates as well.

[0039] In view of the above, the Inventors have recognized the benefits of a method for freezing a material during the lyophilization process wherein a fluid is flowed from a first plurality of fluid flow inlets across a lyophilization tray in a first direction towards a lower opening disposed between one or more baffles, flowing the cooling fluid from a second plurality of fluid flow inlets across the lyophilization tray in a second direction towards the lower opening, and directing the cooling fluid towards one or more fluid flow outlets with the one or more baffles. The baffles may extend from an upper portion of an internal chamber toward a lyophilization tray that is disposed in towards a lower portion of the internal chamber, thereby drawing fluid past the lyophilization tray before it enters the lower opening. The method may further comprise recycling the cooling fluid, e.g., by flowing the cooling fluid from the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

[0040] According to some embodiments, the disclosure relates to a lyophilization freezing module, e.g., that may be used with a method that realizes the advantages described above. In some embodiments, the lyophilization freezing module comprises one or more baffles extending from an upper portion of the internal chamber towards a lower portion of the internal chamber, wherein the one or more baffles are configured to prevent direct flow from the first plurality of fluid flow inlets and the second plurality of fluid flow inlets to the one or more outlets. The freezing module may comprise a first plurality of fluid flow inlets positioned on a first side of the internal chamber and a second plurality of fluid flow inlets positioned on a second side of the internal chamber opposite from the first side. The lyophilization module may comprise one or more fluid flow actuators configured to create a flow of fluid from the internal chamber through the one or more outlets, through one or more flow passages, and back into the8#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 internal chamber through the first plurality of fluid flow inlets and the second plurality of fluid flow inlets. In some embodiments, the module comprises one or more fluid flow outlets fluidly coupled to internal chamber, the first plurality of fluid flow inlets, and the second plurality of fluid flow inlets. The lyophilization freezing module may comprise a housing including an internal chamber and a base configured to be disposed on a supporting surface. In some embodiments, the module comprises a passage a passage extending through the housing with a first opening and a second opening configured to permit movement of a lyophilization tray through the passage, e.g., through which a lyophilization tray may be passed.

[0041] As mentioned previously mentioned, it may be desirable to maintain a majority of a flow of cooling gas to be directed across the one or more containers contained within an internal volume of the housing of a module. However, the relative position of the one or more containers may have a significant influence on fluid flow (e.g., as described in the working examples, below), and the general flow of fluid past the containers is relatively high resistance compared to a direct path towards the outlet. Using one or more baffles as described herein, the person of ordinary skill can increase the resistance of direct fluid flow pathways, eliminating paths of lower resistance so that the most efficient path for fluid flow carries the flow from multiple directions towards the lyophilization tray rather than directly to the outlet. Depending on the relative position of the one or more baffles, fluid flow can be altered, e.g., by increasing the resistance of direct flow-paths until flow past the containers is favored. Thus, in the lyophilization freezing module described above, the first cooling fluid flow and / or the second cooling fluid flow may be directed towards the containers within a module and / or towards the bottom of the chamber (relative to gravity) using one or more baffles prior to extraction from the module. For example, in some embodiments, baffles are arranged so that fluid flow must be directed past the samples before rising vertically.

[0042] The lyophilization module may comprise one or more baffles extending from an upper portion of an internal chamber of the lyophilization freezing module, towards a lower portion of the internal chamber. The baffle(s) may extend downward (relative to gravity) towards a vertical position above the bottom of the chamber but below the vertical position of the top of a vial containing lyophilization sample, when one or more vials or other containers (e.g., a plurality of vials) is inserted into the chamber. The one or more baffles may leave a lower opening through which the first cooling fluid flow and / or the second cooling fluid flow will tend9#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 to flow to reach the one or more outlets. The lower opening may be situated at the vertical position above the bottom of the chamber but below the vertical position of the top of the vial. Depending on the embodiment, the vertical position of the lower opening could be chosen to accommodate containers (e.g., vials) sized for lyophilization in the lyophilization freezing module. As a specific, non-limiting example, in some embodiments the one or more baffles could form a fluid conduit extending from the one or more chamber outlets to the lower opening, such that the only path to the one or more outlets forces the cooling fluid through the lower opening, thereby forcing the cooling fluid past the samples in one or more vials in the lyophilization freezing module. As another non-limiting example, in some embodiments the one or more baffles simply limit fluid flow (e.g., allowing a small amount of leakage past the baffles) but still block one or more direct flow paths between at least some inlets and outlets.

[0043] According to some embodiments, a lyophilization freezing module is configured to recirculate at least a portion of the cooling fluid that flows into the one or more outlets. In some embodiments, the cooling fluid from the one or more fluid flow outlets is flowed from the one or more fluid flow outlets to the one or more fluid flow inlets. The recirculated cooling fluid may be cooled during recirculation, e.g., by mixing colder cooling fluid with the recirculated cooling fluid, or by refrigerating the cooling fluid by any of a variety of appropriate methods. Thus, the cooling fluid entering the one or more fluid flow inlets may, in some embodiments, be relatively cooler than the cooling fluid exiting the one or more outlets of the lyophilization freezing module, according to some embodiments.

[0044] The systems and methods provided herein may have various advantages for conditioning, nucleation, and freezing during lyophilization. Furthermore, the systems and methods provided herein may advantageously be compatible with modular lyophilization systems. As elaborated upon below, in some embodiments, a system or method provided herein may be used to cool a plurality of containers (e.g., vials) stored in a tray configured to move through a lyophilization system. In some embodiments, the systems and methods provided herein modulate cross flow of cooling fluid around a plurality of vials or other containers. The cooling fluid may, in some embodiments, be collected, redirected, temperature adjusted, and / or directed back to the vials or other containers. Various features of the system relate to controlling the temperature of the cooling fluid, including but not limited to injection of additional cooling fluid to adjust temperature of redirected / recycled gas, and / or ejection of fluid to compensate for10#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 additional injected cooling fluid to maintain system pressure at desired set point. Other aspects and advantages of the present disclosure are elaborated upon in greater detail below.

[0045] Forced convection provides a variety of advantages for cooling containers (e.g., vials), including but not limited to a non-contact cooling method for freezing the vials or other containers. Forced convection may be advantageous, for example, because it may be compatible with a maglev system used to transport containers through a lyophilization system. An inert fluid (e.g., an inert gas) may be cooled to the target temperatures for the freezing process and blown through the containers to reduce their temperature through convective cooling. The containers can move freely through this fluid flow regime without requiring additional actuation or generating potential contaminants. The temperature can be controlled to create similar cooling profiles to existing shelf-based conduction systems, but it can also change temperature more quickly than a shelf because the fluid has less thermal mass than the shelf. Because of the controllability and compatibility of forced convection for cooling in a continuous lyophilizer, according to at least some embodiments, forced convection is used in various systems and methods provided herein. Any of a variety of suitable fluids may be used, including but not limited to nitrogen gas and noble gasses (e.g., helium, argon). Nitrogen may be used as the convective gas, in some embodiments, because it is inert and relatively easy to source.

[0046] According to some embodiments, a lyophilization system comprises a cooling fluid source. The cooling fluid source may be configured to supply additional cooling fluid to a lyophilization freezing module as desired. The cooling fluid source may be configured to be selectively fluidly coupled to one or more fluid flow inlets of the lyophilization freezing module. For example, the cooling fluid source may be configured to be selectively fluidly coupled to a first plurality of fluid flow inlets and / or a second plurality of fluid flow inlets. The coupled cooling fluid source may, in some embodiments, be used to flow cooling fluid into the internal chamber.

[0047] Fluid flow within a system or method provided herein may be actuated using any of a variety of suitable fluid flow generation mechanisms. A system’s performance is highly dependent, according to some embodiments, on the mechanism used to generate the fluid flow. Suitable fluid flow generators may include but are not limited to fluid flow actuators (e.g., fans, blowers) that may be configured to generate fluid flow. Any of a variety of fluid flow actuators may be used, depending on the embodiment. For example the fluid flow actuators may be a11#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 positive displacement pump (e.g., a diaphragm pump, a piston pump, a rotary vane pump, or a peristaltic pump) a dynamic pump (e.g., a fan, a blower), or a pressurized fluid source (e.g., a compressed gas tank).

[0048] Actuators may be advantageous for fluid flow generation, e.g., because fluid flow actuators may maintain consistent performance over longer periods of time, whereas in at least some embodiments cooling fluid sources drain over time. Fluid flow actuators may be small or large. According to some embodiments, fluid flow can be generated centrally with a large actuator that creates a pressure head to drive flow through all the chambers of a system. In some embodiments the flow can be generated locally with small actuators positioned at a specific site. The use of a large actuator may reduce the number of actuators used, according to some embodiments (e.g., because a single actuator may be used for the whole system). However, the use of a smaller number of large actuators may constrain the ductwork design, e.g., where a large, central actuator requires more complex piping to distribute the fluid flow amongst all the chambers. This piping may become unwieldy when integrated into a system which recycles the used fluid, whereby the flow must be redirected back to the blower from all the chambers. Local flow generation, e.g., by using more actuators to generate separate flow actuation in each chamber, avoids these constraints, e.g., by introducing separate, smaller recycling systems to operate on each chamber. The local flow generation strategy is used, according to some embodiments, because it lends itself particularly well to modularity, e.g., where each recycling system is fully integrated into a single module. Modular recycling thus provides more flexibility in using this cooling system in a larger lyophilization system.

[0049] Once a suitable actuator for the system is chosen, the specific flow generation hardware may be selected. The local flow generation strategy uses small actuators, according to some embodiments for driving fluid flow. Muffin fans may be a good choice for this flow actuator because they have been highly developed for cooling in the computer industry. Choosing fans, which could provide an order of magnitude faster flow in ideal conditions, increases the likelihood that the fans will maintain required performances when operating in the non-ideal conditions created by the chamber hardware, such as head losses created by the fluid recycle ductwork, according to some embodiments.

[0050] Fluid flow actuators provided herein may be configured to provide any of a variety of suitable fluid flow velocities into the chamber of a lyophilization freezing module,12#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 depending on the embodiments. For example, according to some embodiments, a fluid flow actuator is configured to maintain a fluid velocity of greater than or equal to 0.5 m / s, greater than or equal to 1 m / , greater than or equal to 1.5 m / s, greater than or equal to 2 m / s, greater than or equal to 2.5 m / s, greater than or equal to 3 m / s, greater than or equal to 3.5 m / s, greater than or equal to 4 m / s, greater than or equal to 4.5 m / s, greater than or equal to 5 m / s, greater than or equal to 5.5 m / s, greater than or equal to 6 m / s, greater than or equal to 6.5 m / s, greater than or equal to 7 m / s, or greater than or equal to 7.5 m / s at the inlet opening. In some embodiments, a fluid flow actuator is configured to maintain a fluid velocity of less than or equal to 8 m / s, less than or equal to 7.5 m / s, less than or equal to 7 m / s, less than or equal to 6.5 m / s, less than or equal to 6 m / s, less than or equal to 5.5 m / s, less than or equal to 5 m / s, less than or equal to 4.5 m / s, less than or equal to 4 m / s, less than or equal to 3.5 m / s, less than or equal to 3 m / s, less than or equal to 2.5 m / s, less than or equal to 2 m / s, less than or equal to 1.5 m / s, or less than or equal to 1 m / at the inlet opening. Combinations of these ranges are also possible (e.g., greater than or equal to 0.5 m / s and less than or equal to 8 m / s, or greater than or equal to 1 m / and less than or equal to 4 m / s). Other ranges, both higher and lower than those described above, are also possible, as the disclosure is not so limited. In situ, the fluid speed at the chamber inlet, in front of the fans, may be between 1 and 4 m / s.

[0051] Fluid flow actuators may be configured to operate at relatively low working temperatures (e.g., to actuate the flow of relatively cold fluids). For example, one risk in using the muffin fans positioned directly on the chambers is that they may be directly exposed to temperatures as low as -80°C during the freezing chamber operation. Because the fans are at the chamber, the fluid passing through them may be as cold as the temperature within the chamber. Without wishing to be bound by any particular theory, the temperature tolerance of smaller actuators for modular recycling systems may be higher than for actuators of a central fluid actuation system. For example, if the actuators were further from the chamber, such as with a central blower, then the fluid could warm up on its way back to the blower before being cooled down again as it returns to the chamber. While this central blower system would be less energy efficient, it would not risk exposing the blower to temperatures outside of its rated operating range. Actuators that become too cold may fail in any of a variety of ways, e.g., the lubricant in their bearings could stiffen, causing them to prematurely wear out and fail.13#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0052] Accordingly, fluid flow actuators may be selected to be appropriate for the working temperatures of the fluid they control. For example, where fans such as muffin fans are used, the coils in the fans may generate heat while they are operating, e.g., to heat themselves and thereby compensate for the cooling from the fluid. This heating may sufficiently compensates for the heat transfer to the fluid such that the fans are not overcooled. In some embodiments, the actuators may be insulated and / or actively heated using one or more associated heaters to prevent the cold from damaging core components of the actuators. In other embodiments, such insulation or active heating may be unnecessary, e.g., where a fluid flow actuator was designed with cold-resistant components or designs. In some embodiments, a fluid flow actuator is configured to actuate fluids at temperatures of greater than or equal to -80 °C, greater than or equal to -70 °C, greater than or equal to -60 °C, greater than or equal to -50 °C, greater than or equal to -40 °C, greater than or equal to -30 °C, greater than or equal to -20 °C, or greater than or equal to -10 °C. In some embodiments, a fluid flow actuator is configured to actuate fluids at temperatures of less than or equal to 0 °C, less than or equal to -10 °C, less than or equal to -20 °C, less than or equal to -30 °C, less than or equal to -40 °C, less than or equal to -50 °C, less than or equal to -60 °C, or less than or equal to -70 °C. Combinations of these ranges are also possible (e.g., greater than or equal to -80 °C and less than or equal to 0 °C, or greater than or equal to -70 °C and less than or equal to -10 °C). Other ranges, both higher and lower than those described above, are also possible, as the disclosure is not so limited.

[0053] In some embodiments, the lyophilization system comprises a cooling fluid sink. The cooling fluid sink may be configured to remove cooling fluid from the lyophilization freezing module, e.g., to prevent the lyophilization freezing module from becoming overpressurized by the addition of new cooling fluid. For example, in some embodiments, the lyophilization system (e.g., as part of the lyophilization freezing module) comprises a pressure activated exhaust port configured to exhaust fluid from the internal chamber when a pressure of the internal chamber is greater than a threshold pressure.

[0054] In a basic forced convection layout, the cooling fluid is only blown past the containers once through the cooling chamber. This process is thermally inefficient, as the short time during which the fluid and the containers are exposed to each other is not sufficient for both temperatures to equilibrate, particularly at the beginning of the cooling process. Rather than simply eject the waste fluid, the used fluid is reintegrated into the injected fluid flow using a14#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 recycling system. Using this recycling system ensures that fresh fluid does not need to be cooled all the way from ambient temperatures to the system setpoint; instead, fluid which is already close to the system setpoint can be reduced back to the target temperature, requiring much less cooling power. The recycling system also reuses the fluid mass, which saves on raw material costs. The recycling system includes a metered inlet and a passive outlet. The metered inlet is used to control the cooling provided to the recycled fluid flow to maintain the setpoint temperature within the chamber. The passive outlet ensures that mass leaves the system to account for the mass added through the metered inlet, preventing pressure buildup within the chamber.

[0055] In some cases, the lyophilization freezing module comprises a diffuser fluidly coupling one or more outlets of the lyophilization freezing module to one or more inlets of the lyophilization freezing module. The diffuser may, for example, fluidly connect all fluid flow outlets of the lyophilization freezing module to all fluid flow inlets of the lyophilization freezing module. The diffuser may allow fluid flows from separate fluid flow outlets to mix before the fluid is returned to the one or more fluid flow inlets of the lyophilization freezing chamber, according to some embodiments.

[0056] Any of a variety of types of diffuser may be used. For example, the diffuser may be a porous diffusor (e.g., a porous metal diffuser, a porous ceramic diffuser, or a porous polymeric diffusor). In some embodiments, the diffuser is a membrane diffusor. In some embodiments, a single diffusor is used, e.g., such that the fluid from all of the one or more outlets passes through the single diffuser. However, multiple diffusers may also be used, as the disclosure is not so limited.

[0057] The lyophilization freezing system may comprise ductwork, according to some embodiments. For example, in some embodiments, a lyophilization freezing system comprises a fluid recycling system comprising one or more recirculation ducts and a diffuser. The system may be configured to recycle fluid such that fresh fluid enters the recycling system through one or more fluid flow inlets to a lyophilization freezing chamber connected to the one or more ducts. The system may further comprise a diffuser. In some embodiments, the system maintains constant pressure by expelling fluid through an outlet attached to the diffuser. The ducts, diffuser, and outlets may be connected to each other using any of a variety of appropriate fluid- tight seals, e.g., O-ring seals, which would be known to those of ordinary skill in the art.15#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0058] As discussed above, in some embodiments the lyophilization freezing module comprises an internal chamber. The chamber may be configured to house a lyophilization sample. The chamber may, for example, have appropriate dimensions to allow a lyophilization tray to rest within the chamber. The chamber may have one or more openings (e.g., through which a lyophilization sample or a plurality of lyophilization samples may be passed during a lyophilization operation). In some embodiments, the openings of the chamber may be closed (e.g., using one or more doors) such that a cooling fluid recycling system can be operated without drawing ambient gasses into the chamber during sample freezing. This may, advantageously, allow efficient recycling of fluid within the chamber.

[0059] In some embodiments, the lyophilization freezing module comprises a housing. The housing may bound at least a portion of the chamber of the lyophilization freezing module. In some embodiments, the housing is configured to maintain the position of one or more lyophilization freezing module components. For example, the one or more fluid flow inlets and / or the one or more fluid flow outlets of the lyophilization freezing module may be formed in the housing, or else may be rigidly coupled to the housing. The housing may comprise a bottom surface of the chamber, on which a lyophilization sample or a plurality of lyophilization samples may be rested. Thus, in some embodiments the housing is configured to support a lyophilization tray at a vertical location relative to the base, wherein the vertical position is suitable for a baffle configuration as described above. In some embodiments, the housing is configured so that a lyophilization tray rests between a first plurality of fluid flow inlets and a second plurality of fluid flow inlets when rested on the bottom surface of the housing.

[0060] The housing may be configured to facilitate use of a lyophilization freezing module in a modular lyophilization freezing system. For example, in some embodiments, the lyophilization freezing module is configured to be connected to one or more adjacent housings of one or more adjacent lyophilization modules. In some such embodiments, the coupled lyophilization modules may be used together to lyophilize a sample (e.g., by freezing the sample in a lyophilization freezing module and drying the sample in a connected lyophilization module.

[0061] In some embodiments, a modular lyophilization freezing system is configured to transport a lyophilization sample (e.g., within a lyophilization sample) between adjacent modules of the lyophilization freezing system. Although any of a variety of methods may generally be used to transport the lyophilization sample, advantages have been recognized for the use of non-16#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 mechanical methods of moving a lyophilization sample. For example, by avoiding mechanical components, the risk of sample contamination or mechanical breakdown is significantly reduced. Thus, according to some embodiments, advantages have been recognized for the use of an electrodynamic suspension system configured to move a lyophilization tray through a lyophilization freezing system. In some embodiments, a lyophilization freezing system provided herein comprises a plurality of stators configured to move a magnetic mover (e.g., which may be coupled to a lyophilization tray). In some embodiments, the plurality of stators is configured to move the magnetic mover through a passageway of the lyophilization system. The passageway may be at least partially defined by the internal chamber of the lyophilization freezing module, depending on the embodiment. Thus, in some embodiments the plurality of stators is configured to guide a lyophilization tray into or out of the lyophilization freezing module.

[0062] Turning to the figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described relative to these embodiments may be used either individually and / or in any desired combination as the disclosure is not limited to only the specific embodiments described herein.

[0063] FIG. 1 provides a non-limiting, schematic, side-view illustration of fluid flows that may be involved in cooling non-limiting lyophilization freezing module 101 comprising chamber 102, according to some embodiments. In particular, FIG. 1 illustrates how fluid may be recycled through the chamber using recycling loops 103. As illustrated, recycling fluid can be looped from one or more outlets (not shown) of internal chamber 102 of lyophilization freezing module 101 to one or more inlets (not shown) of lyophilization freezing module 101 using one or more recycling loops of cooling fluid. As shown, fluid flows out of chamber 102 from the top of the chamber, e.g., by passing from the one or more outlets through ductwork that passes through the top of chamber 102, or by passing through outlets disposed at the top of chamber 102. As discussed above, the fluid leaving the chamber may be passed through one or more diffusors, which may mix (e.g., homogenize) the fluid before it is separated into recycling streams 103 and recirculated to the inlets of lyophilization freezing module 101. Although in some embodiments all the fluid exiting the chamber is recycled, according to some embodiments, a portion of the fluid is exhausted via exhaust stream 107, thus exiting the recycling system. In some embodiments, the system further comprises an exit valve that can be used to exhaust fluid from the lyophilization freezing system, e.g., to compensate for fluid added.17#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0064] To replace exhausted fluid, and / or to alter the pressure of lyophilization freezing module 101, fluid may be added to lyophilization freezing module 101. The added fluid may be added directly to the chamber, or may be added to the chamber via a recycling loop. For example, in FIG. 1 , additional fluid from a fluid source (not shown) is supplied, as indicated by fresh feed arrows 105, representing the flow of a fresh feed of fluid into the recycling loops.

[0065] In FIG. 1, fluid passing through recycling loops 103, optionally mixed with fresh fluid from fresh feeds 105, is recycled back to chamber 102. The fluid re-enters chamber 102 via one or more inlets located on each side of chamber 102. By entering the fluid on both sides of chamber 102, the fluid may be used for multidirectional cooling, which may be beneficial for lyophilization, as explained above.

[0066] FIGS. 2A-2B provide a non-limiting, schematic perspective illustration of a fluid recycling system 201, according to some embodiments. Recycling system 201 may be configured to direct fluid flows as schematically illustrated in FIG. 1. FIG. 2A illustrates various elements of recycling system 201, some of which are partially transparent in the figure for the sake of clarity. Recycling system 201 is configured to be coupled to a chamber of a lyophilization freezing module, and comprises a first plurality of inlets 221a and a second plurality of inlets 221b; each inlet is configured to supply fluid to the chamber interior. Recirculation ducts 203 recirculate fluid flow into through the chamber interior (not shown). Fluid from the chamber interior then exits the chamber via one or more outlets located at underside 223 of diffuser 211.

[0067] During use of recycling system 201 , the one or more outlets located at underside 223 of diffuser 221 may be the sole route for fluid to exit the internal chamber of the freezing module. Diffuser 211 diffuses fluid from one or more outlets of the chamber before directing the fluid into recirculation ducts 203. It should, of course, be understood that a diffuser is not necessary for all embodiments, and that the one or more outlets may instead lead directly into recirculation ducts 203, in some embodiments.

[0068] Once in one of recirculation ducts 203, fluid from the one or more outlets may be passed to inlets 221a or 221b. In some embodiments, the recycling system is configured to exhaust some of the fluid and / or to admit additional fluid, e.g., in order to maintain a consistent pressure and temperature. Recycling system 201, for example, comprises gas conduit 213, which is configured to feed coolant fluid from a coolant fluid source into the recirculation ducts via18#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 manifolds 205. Once added, the fluid mixes with the fluid from the outlets located at 223, and is transmitted to inlets 221a or 221b where it passes into the internal chamber of the lyophilization freezing module. And fluid recycling system 201 further comprises exhaust tube 207 through which fluid can exit the fluid recycling system. The ordinary artisan would recognize, of course, that this arrangement is non-limiting, and that new fluid could be added anywhere in the recycling system (or else, could be added directly to the chamber interior); likewise, exhaust could be released from anywhere in the recycling system (or else, could be removed directly from the chamber interior) as the disclosure is not so limited.

[0069] FIG. 2B schematically illustrates the flow of fluid through fluid recycling system 201. The direction of fluid flow is represented by flow arrows 271. As shown, fluid passes into the internal chamber via inlets 221a and 223a at points 251a and 251b, respectively. The fluid passes into diffuser 211 at point 253, where it is mixed and homogenized before splitting into first fluid flow 255a and second fluid flow 255b as it enters recirculation ducts 203. A portion 275 of the fluid leaving diffuser 211 passes through exhaust tube 207 to exit recycling system 201. To replace it, fluid 273 is flowed into manifolds 205, which introduce the fluid flow across the width of recirculation duct 203, so that it can mix with fluid flows 255a and 255b. The resulting fluid mixture then returns to inlets 251a and 251b, where it returns to the internal chamber.

[0070] FIG. 3 provides a close-up illustration of the manifolds 205 as illustrated in FIG. 2A, according to some embodiments. As illustrated, the manifold is configured to evenly distribute fluid across the width of the recirculation duct. The fluid may be supplied to the manifold in liquid or gaseous form. In some embodiments, the fluid is a liquid (e.g., a cryogenic liquid) that evaporates as it leaves the manifold.

[0071] In the figure, the uniformity is achieved by passing the fluid through a plurality of holes 281 that are regularly spaced along the width of manifold 205. Manifold holes 281 may point upwards relative to gravity. This orientation, in at least some cases forces fluid (e.g., liquid nitrogen) which enters the manifold to be carried by the gaseous fluid flow out of the manifold holes, homogenizing the fluid distribution. When the manifold holes are oriented downwards, any liquid which enters the manifold may fall out of the manifold preferentially through the holes closest to the fluid source, leading to a thermal gradient across the recirculation duct. The manifold may be covered with a mesh (e.g., a fine stainless-steel mesh). The mesh may, in some19#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 cases, helps to break up large liquid (e.g., liquid nitrogen) droplets as they exit the manifold. This mesh may helps the liquid quickly flash and cool down the gas in the duct(s) to reduce the risk of the liquid travelling all the way through duct and into the cooling chamber.

[0072] However, it should be understood that, for example, porous manifolds or other manifold designs could be used to achieve uniform fluid distribution, as the disclosure is not so limited. Uniform distribution of added fluid may help ensure that the temperature profile across the recirculation duct remains uniform, homogenizing the temperature of cooling fluid and helping to standardize lyophilization.

[0073] It should generally be understood that the geometry and configuration of the ductwork, diffuser, manifolds, exhaust valve, and fluid flow paths in FIGS. 2A-3 is not limiting, and the person of ordinary skill could readily conceive of alternative arrangements or shapes for these components, according to some embodiments, without limiting the efficacy of the fluid recycling system.

[0074] The fluid flow within the recycling system may, in some embodiments, be driven by fluid flow actuators (e.g., muffin fans) within the system. The fluid flow actuator may help to promote recirculation, since use of a fluid source without a fluid flow actuator could reduce the tendency of the cooling fluid to re-enter the recirculation ducts, reducing the effectiveness of recycling the fluid flow.

[0075] Components of recycling system 201 may be made from any of a varity of suitable materials. For example, ducts 203 and diffuser 211 may be made from any of a variety of appropriate materials. In some embodiments, some or all of the components of the recycling system are made from the same material. Use of the same material may, advantageously, limit thermal expansion mismatch between distinct components. For example, use of the same material for the ducts and / or the diffusor may limit thermal expansion mismatch and reduce stress on both components. In some embodiments, components of the recycling system (e.g., ducts and / or the diffuser) are made from a metal, e.g., aluminum. In some embodiments, one or both of the ducts and diffuser are made from welded 1 / 16in aluminum sheets.

[0076] The recycling system can be joined to the chamber by any of a variety of appropriate sealing methods. In some embodiments, the ducts and / or the diffuser are configured to seal to the chamber via the use of an O-ring or a gasket. According to some embodiments, the recycling system comprises a flange adjacent to its inlets and / or its outlets, which is used to20#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 connect the recycling system components to each other and to the cooling chamber. The flange is used to compress the O-rings used to seal the components together, in some cases. For example, referring back to FIG. 2A, recirculation ducts 203 comprises flanges 237 surrounding inlets 221a and 221b and the chamber outlets (not visible) located at position 223 below diffusor 211 configured to be bolted to the lyophilization freezing module by passing fasteners (e.g., bolts, screws, etc) through holes 239 of flanges 237. The bolts, when tightened, compress O-rings 241 against the chamber, providing a pressure-seal for the recycling system.

[0077] While hole-fastening is contemplated in the specific embodiment of recycling system 201 , it should of course be recognized that any of a variety of other fastening methods (e.g., clamping, riveting) or other methods of securing the recycling system (e.g., welding, soldering, adhesion) may be used, as the disclosure is not so limited

[0078] The recycling system components may match complementary components of a lyophilization freezing module to reduce the risk of differential thermal contraction creating stress on the sealed interfaces, which could lead to deformation and leaks, in some cases. For example, in some embodiments, both the chamber and the recycling system are made from aluminum. When the chamber is made from a different material, such as stainless steel, then it may be advantageous for the recycling system components to be made from the same material to maintain this thermal expansion coefficient matching.

[0079] In some embodiments, the size and shape of the recycling system is chosen to compensate for mismatched thermal expansion between the recycling system and the lyophilization freezing module. Such an arrangement may help maintain the integrity of the seal (e.g., the O-ring seal or the gasket seal) of the recycling system to the lyophilization freezing module. For example, the recycling system may have a spring-like configuration that distributes thermal strain across a comparatively large portion of the recycling system, e.g., to keep deformation of the recycling system in the elastic regime. The “C” shape of recirculation ducts 203 may be particularly advantageous, e.g., because it may provides flexibility for the ducts to bend in response to differential thermal contraction.

[0080] Fresh fluid can be introduced into the recycling system or the lyophilization freezing module in any of a variety of suitable ways, including by a manifold, as discussed above. Fresh fluid (e.g., nitrogen gas) is injected into the recycling system through manifolds in the recirculation ducts, as shown in FIG. 3, according to some embodiments. These manifolds21#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 may, in some cases, distribute the fluid injection across the width of the ducts, leading to uniform temperature fluid flow across the containers in front of the fans. The manifolds may be made from any of a variety of appropriate materials. In some embodiments, the manifolds are made from aluminum tubes with evenly spaced holes drilled into one side.

[0081] In some embodiments, the manifold is configured to be mechanically connected to the recirculation duct. For example, at least a portion of the manifold, such as ends of the tube of a manifold, may be threaded in order to help them mechanically couple to the recirculation duct, a fluid connection, or an end-cap. The tube may be threaded on each end. In some embodiment, the manifold is configured to prevent direct contact of the fluid therein with the wall of the recirculation duct (prior to release of the fluid from the manifold). For example, an end of the manifold may be capped, according to some embodiments. Referring to manifold 205 of FIG. 3, end 261a has an aluminum cap threaded on it, according to some embodiments, to force fluid flow through the manifold holes rather than letting fluid jet through the tube and hit the recirculation ducts’ side wall 263. Other end 261b threads into a threaded elbow 265used to mount the manifold to the recirculation duct and to supply manifold 205 with fluid.

[0082] The manifold assembly may, like the ductwork, be advantageously made from the same material as the chamber to reduce thermal mismatch. Likewise, it may be advantageous for the manifold and the ductwork to be made from the same material.

[0083]

[0084] FIG. 4 provides a non-limiting, schematic cross-section of lyophilization freezing module 400, according to some embodiments. As shown, lyophilization freezing module 400 is coupled to recirculation ducts 203 of recycling system 201 (as shown in FIGS. 2A-3) at seals 461. Although lyophilization freezing module 400 is configured to couple to fluid recycling system 201 of FIGS. 2A-3, it should of course be understood that the lyophilization freezing module need not be used with a fluid recycling system and could generally be arranged to work with any of a variety of fluid flow actuators and / or fluid sources for cooling lyophilization samples inserted into the chamber.

[0085] As shown, lyophilization freezing module 400 comprises housing 401 including an internal chamber 403. Beneath internal chamber 403, lyophilization freezing module 400 further comprises base 405, which is configured to be disposed on a supporting surface. Internal chamber 403 is configured to hold one or more lyophilization trays 411, optionally holding one22#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 or more lyophilization samples 413, on a bottom surface of the chamber. In some embodiments, the internal chamber forms a portion of a passage extending through the housing with a first opening and a second opening configured to permit movement of a lyophilization tray (optionally containing one or more lyophilization samples) through the passage. For example, in some embodiments, the lyophilization freezing module is configured to transport one of lyophilization trays 411 into chamber 403 through a first opening behind the cross-section shown in the figure and through a second opening in front of the cross-section shown in the figure, wherein the first opening and the second opening open into the passageway. In some embodiments, the tray rests on the base during lyophilization; in other embodiments, the tray is levitated above the base, e.g., by a stator during lyophilization.

[0086] Lyophilization freezing module 400 is configured to freeze the one or more samples disposed therein, e.g., by recycling coolant fluid through internal chamber 403. As shown in FIG. 4, the lyophilization freezing module comprises one or more fluid flow inlets 423. The one or more fluid flow inlets may be configured to supply coolant fluid to internal chamber 403. For example, the pictured lyophilization freezing module comprises a first plurality of fluid flow inlets 423 (corresponding to flow inlets 221a of FIG. 2 A) positioned on the left side of internal chamber and a second plurality of fluid flow inlets 423 (corresponding to flow inlets 221b of FIG. 2A) positioned on the right side of the internal chamber. (Only one inlet of each plurality is shown, since the figure is a schematic cross-section.) The lyophilization freezing module further comprises one or more fluid flow outlets 425 fluidly coupled to the internal chamber. For example, in FIG. 4, the lyophilization freezing module comprises a plurality of outlets 425 (although only one is visible because the figure is a schematic cross-section). As indicated by fluid flow arrows 421, lyophilization samples 413 are cooled, when present, by passing fluid from inlets 423 across samples 413, where the fluid absorbs heat from the samples (thereby cooling them) and to outlets 425. The fluid passed through outlets 425 is subsequently cooled and recycled back to inlets 423 using recycling system 201, according to some embodiments, e.g., via the exhausting of at least a portion the fluid exiting outlet 425, followed by the addition of cold coolant fluid in a recirculation duct.

[0087] Lyophilization freezing module 400 of FIG. 4 is configured to direct fluid towards lyophilization samples 413, when present. For example, lyophilization freezing module 400 is configured to direct fluid preferentially along flow paths 421 from inlets 423 to outlets 425,23#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 while substantially preventing fluid flow along paths 427. This control may be achieved using one or more baffles 431 extending from an upper portion of the internal chamber towards a lower portion of the internal chamber, wherein the one or more baffles 431 are configured to prevent direct flow 427 from the first plurality of fluid flow inlets and the second plurality of fluid flow inlets to the one or more outlets. As shown, baffles 431 extend from vertically above to vertically below an upper portion of the first (left) plurality of flow inlets 423 and an upper portion of the second (right) plurality of flow inlets 423, relative to the base 405 of the chamber, and relative to gravity. The baffles, as shown, also extend from vertically above to vertically below an upper portion of the lyophilization containers (illustrated as vials) 413 present in the chamber. This baffle arrangement may, in some embodiments, ensure that fluid flows along paths like paths 421, improving cooling efficiency of the fluid. As shown, in some embodiments, it is advantageous to use two or more baffles 431 disposed on opposite sides of an outlet or plurality of outlets, particularly in the context of multidirectional fluid flow of the type illustrated. It should, of course, be understood that such arrangements are not strictly necessary. For example, in some embodiments, a single baffle (e.g., in the shape of a loop surrounding the one or more fluid flow outlets) could be used, so that baffles 431 shown in FIG. 4 are different cross-sections of a single baffle that loops out of the plane to connect them. Other baffle arrangements are also possible, as the disclosure is not so limited.

[0088] The one or more baffles may leave a lower opening through which the first cooling fluid flow and / or the second cooling fluid flow will tend to flow to reach the one or more outlets. For example, baffles 431 leave lower opening 434 situated at a vertical position above the bottom of chamber 403 but below the vertical position of the top lyophilization samples 413, so that fluid drawn to outlets 425 must be drawn through lower opening 434 and must thus pass by lyophilization samples 413 along paths 421, rather than passing above them via paths 427.

[0089] The lyophilization freezing module may include baffles to direct the cooling fluid flow for more efficient convective cooling. Without wishing to be bound by any particular theory, the baffles may effectuate improved sample cooling by modulating the fluid resistance of various fluid flow pathways from inlets 423 to outlets 425. Given a box with flow inlets and outlets, the gas may preferentially flow from the inlets to the outlets in the path of least resistance. In the chamber geometry of FIG. 4, the inlet ports are located near the bottom of the side walls and the outlet port is in the middle of the top ceiling. With this layout and no24#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 obstructions, the flow will preferentially move vertically (e.g., along paths 427) towards the outlet before traversing across the bottom portion of the chamber along paths 421, potentially missing some of the vials, according to some embodiments. This disparity would only be magnified with the presence of lyophilization samples 413 in internal chamber 403, as lyophilization samples 413 create further obstructions along the bottom portion of the chamber, which would direct the flow upwards sooner. With multiple rows of vials, flow along paths 427 may lead to significant thermal non-uniformity between the rows, as any row not directly exposed to the cooling gas front would see much less fluid flow, leading to much longer cooling times.

[0090] The Inventors have recognized, in the present disclosure, that closing fluid flow pathways like pathways 427, e.g., by obstructing fluid flow along these pathways, can shunt fluid closer to lyophilization samples 413, thereby improving cooling. Adding baffles 425 to the outlet port, extending the outlet entrance down to the level of the fluid in the vials, increases the resistance for the fluid flow that would bypass the vials by going above them. Rather than traveling along a free path to the outlet, fluid initially flowing along paths 427 is redirected up back down through a narrow gap between the lyophilization tray(s) 411 and baffles 431. In this configuration, path 421, passing between lyophilization samples 413, becomes preferential, directing the cold fluid flow between lyophilization samples 413 and creating more uniform cooling amongst the rows of samples.

[0091] One challenge of this approach is that the bottom of baffles 431 , around which fluid flows, may be subjected to relatively high forces from the fluid. Undamped, these forces can cause vibration and may cause physical interference between the lyophilization samples and the baffles. In some embodiments, the baffles are mechanically reinforced to prevent them from vibrating. The baffles may, for example, include spacers located at their bottom corners to help them resist the force created by the fluid flow at the large flat wall area. The spacers may help to maintain the distance between baffles 431, e.g., by extending between baffles 431 or by bracing baffles 431 against housing 401. Without these spacers, the walls may vibrate and risk interfering with the vials in the system. Of course, it should be appreciated that spacers need not be used, e.g., where the system is toleranced to allow baffle vibration or where baffles 431 are crosssections of a single, looped baffle that surrounds outlets 425.25#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0092] As discussed above, the fluid flow may be actuated using one or more fluid flow actuators (not shown) configured to create a flow of fluid from the internal chamber through the one or more outlets, through one or more passages, and back into the internal chamber through the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

[0093] The temperature in the lyophilization freezing module may be controlled in any of a variety of appropriate ways. In some embodiments, the temperature is controlled using a controller. The fluid flow temperature inside the chamber may be controlled through a cascade controller. The controller may be configured to detect the temperature in the chamber. For example, the lyophilization freezing module and / or the recycling system may comprise a temperature sensor that transmits a signal to the controller.

[0094] The controller may (e.g., in response to a difference between the measured temperature and the target temperature), adjust one or more flow rates of the fluid in the lyophilization freezing system and / or the recycling system in order to adjust the temperature of the lyophilization freezing system. The chamber temperature is controlled, according to some embodiments by metering the mixed liquid and gaseous fluid feed (also referred to herein as a fresh feed flow) into the recycling system. This fresh feed flow rate can be estimated, in some cases, by measuring the flow rate of exhaust fluid out of the recycling system. The flow rate of exhaust can be measured using a flow meter. The fluid exiting the system can safely be warmed up to ambient temperatures, according to some embodiments, advantageously allowing the use of ambient temperature flow meters (rather than cooling-fluid-temperature flow meters) because the fluid exiting the system is not being reused in the cooling system. Thus, exhaust gas is safe to pass through the flow meters, in some embodiments. In a well-sealed system, the exhaust flow rate will equal the manifold inlet flow rate, according to some embodiments.

[0095] As the environmental conditions around the machine change, the amount the fresh liquid nitrogen feed heats up before entering the chamber and the overall heat transfer to the cooling chamber can vary. This variance can result in different fresh feed flow rates being required to maintain the same temperature within the cooling chamber. The cascade controller operating on the outlet flow rate allows the system to compensate for these environmental changes while maintaining the temperature setpoint performance.

[0096] In one aspect, method for freezing a material during a lyophilization process is provided. FIG. 5 provides a non-limiting schematic illustration of method 500 for freezing a26#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 material during a lyophilization process. As indicated, method 500 comprises flowing a cooling fluid from a first plurality of fluid flow inlets across a lyophilization tray in a first direction towards a lower opening disposed between one or more baffles extending from an upper portion of an internal chamber the lyophilization tray is disposed in towards a lower portion of the internal chamber, at 501, and flowing the cooling fluid from a second plurality of fluid flow inlets across the lyophilization tray in a second direction towards the lower opening, at 503. The coolant fluid may be flowed from the first plurality of inlets and the second plurality of inlets simultaneously, in some embodiments, e.g., as indicated by flow arrows 421 in FIG. 4. As discussed above, the flowing of the fluid may be actuated by one or more fluid flow actuators (e.g., fans, pumps).

[0097] Flowing the coolant fluid from both the first plurality of outlets and the second plurality of outlets may, in some embodiments, result in multidirectional cooling of a plurality of lyophilization samples, and may thus confer the benefits of multidirectional cooling, discussed above, which would be absent if flowing coolant at 501 was not performed concurrently with flowing coolant at 503. However, it should, of course, be understood that the simultaneous flow of coolant fluid from the first plurality of outlets and the second plurality of outlets is not required for performance the method. For example, in some embodiments, flowing coolant at 501 and flowing coolant 503 could be performed during non-overlapping and / or partially overlapping time intervals (e.g., by alternating flowing coolant at 501 with flowing coolant at 503 in rapid succession). Thus, the disclosure is not limited by the manner or timing of the flow of coolant from each of the pluralities of inlets.

[0098] Method 500 further comprises directing the cooling fluid towards one or more fluid flow outlets with the one or more baffles, at 505. The direction of the coolant fluid may be passive. The coolant fluid may be directed by, for example, positioning the baffle(s) within the chamber so that they extend from the one or more outlets to a lower opening of the baffle(s) disposed vertically below the top of the lyophilization samples, thereby directing the cooling fluid towards the outlets after it passes through the lower opening of the baffle(s). In some embodiments, the direction of the cooling fluid at 505 is performed simultaneously with flowing coolant fluid at 501 and / or flowing coolant fluid at 503. For example, the flow of coolant fluid from one or both of the pluralities of fluid flow inlets into the chamber may push coolant fluid from the chamber towards the one or more outlets, e.g., by creating a pressure gradient within the27#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 chamber. The coolant fluid pushed towards the outlets may be directed towards the outlets using the baffles.

[0099] According to some embodiments, the method comprises flowing the cooling fluid from the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets, at 507. For example, the coolant fluid may be flowed from the one or more flow outlets to the first plurality of fluid flow inlets and / or the second plurality of fluid flow inlets via one or more recirculation ducts, e.g., as shown in FIG. 4. The flow of fluid from the outlet(s) to the inlets can be performed simultaneously with the steps of flowing coolant fluid at 501 and 503, and / or the step of directing cooling fluid towards the one or more fluid flow outlets at 505. Not all of the fluid from the outlet(s) is passed to the inlet, according to some embodiments. For example, in some embodiments the method comprises exhausting at least a portion of the fluid from the one or more outlets, e.g., to prevent pressure build-up and / or to remove some comparatively warm fluid in order to permit the addition of comparatively cold (e.g., cryogenic) fluid to reduce the temperature of the fluid entering the chamber of the lyophilization freezing module.

[0100] The fluid flowing from the outlet(s) to the inlets may be cooled before reaching the inlets. Optionally, the method may comprise combining a flow of cryogenic fluid with the flow of fluid from the one or more outlets to the first plurality of fluid flow inlets and / or the second plurality of fluid flow inlets (e.g., as a method of cooling the flow), at 509. In FIG. 5, the dashed lines indicate optional method steps. In some embodiments, the flow of cryogenic fluid is controlled in order to control ambient conditions within the lyophilization freezing module (e.g., in response to a pressure or temperature set point for the lyophilization freezing module). For example, in some embodiment, method 500 comprises controlling the flow rate of cryogenic fluid based at least in part on a pressure and / or a temperature within the lyophilization freezing module, at 511. Controlling the rate at which cryogenic fluid is introduce may, advantageously, help to prevent pressure build-up in the lyophilization freezing module. However, actively controlling the flow rate based on target ambient conditions is not necessary. For example, in some embodiments, the ambient conditions in the lyophilization freezing module are controlled passively, e.g., using a pressure actuated exhaust port configured to exhaust fluid from the lyophilization freezing module in response to pressure build-up in the fluid flowing from the one or more outlets. In such systems, cryogenic fluid may be added to the system at a fixed rate,28#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 since pressure build-up resulting from the warming of the cryogenic fluid will actuate the exhaust valve, venting fluid from the system and passively reducing the ambient pressure. In such embodiments, the lyophilization freezing module will reach steady-state, even without active control of the flow rate of cryogenic fluid, and the cryogenic fluid flow rate may simply be set at a value that achieves the desired lyophilization freezing module temperature.

[0101] As indicated by the looped arrangement of method 500, the method may be performed continuously, and some or all of the steps may be performed simultaneously. It should, for example, be appreciated that the combination of the flow of cryogenic fluid with the flow of fluid from the outlet(s) and / or the control of the flow rate of the cryogenic fluid, if performed, may be performed simultaneously with the steps of flowing the cooling fluid from the first plurality of inlets at 501, the flowing the cooling fluid from the second plurality of inlets at 503, the direction of the cooling fluid towards the one or more fluid flow outlets at 505, and / or the flow of coolant fluid from the outlet(s) to the inlets at 507. It should further be understood that other methods of freezing are also possible using the systems and methods provided herein, as the disclosure is not so limited.

[0102] FIG. 6 provides a schematic, top-view illustration of a non-limiting lyophilization system 601 comprising lyophilization freezing modules 603e. Individual lyophilization modules 603 (coded as 603a, 603b, 603c, 603d, 603e, and 603f and patterned based on their role within system 601) are represented as individual squares. A series of arrows 605 and illustrations of movers 607 illustrates the transportation of a tray of vials through the system, according to some embodiments. The transportation of the mover is described in detail below. Lyophilization system 601 of FIG. 6 may be configured to achieve a throughput of about 100 vials / hour.

[0103] Lyophilization system 601 of FIG. 6 includes 6 different types of process stations, each of which may include one or more appropriately chosen lyophilization modules, distinguished visually by patterns in the modules. The first station, loading (modules 603a), is where the schematized system interfaces with other elements of a production line. This station is connected to both the entrance and exit of the machine, according to some embodiments. The vials are carried by movers 607, which do not leave the machine, according to some embodiments. For example, loading modules 603a are configured to loop the beginning of a lyophilization pathway 617a to the end of a lyophilization pathway 617 so that within loading modules 603a, lyophilized vials are removed and fresh vials are added.29#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0104] Sample vials may be added to lyophilization system 601 at one or more of modules 603a, e.g., via the entrance of the machine, to start the lyophilization process the beginning 617a of a lyophilization pathway. The vials may be lyophilized by passing them along the lyophilization pathway described below until they reach the end 617b of the lyophilization pathway, also located in modules 603a, where lyophilized vials are removed. Movers 607 then proceed to beginning 617a while they are reloaded with fresh sample vials, and the process is continued. Connecting the entry and the exit of the system ensures that movers will follow a continuous looping motion to maintain operation through this loading and unloading of vials.

[0105] From beginning position 617a, mover 607 proceeds through a second type of station connecting the loading station to an adjacent station. The second type of station is the load lock (modules 603b), which may separate each process station, or which may separate at least one processing station from another. For example, modules 603b, represented in FIG. 6 as white boxes, are load lock modules disposed between various stations of lyophilization system 601. Unlike most other station types in the represented system, load lock modules (modules 603b) are not positioned adjacent to one another, in most cases. Rather, they are distributed throughout the system, configured to act as airlocks between adjacent modules on either side, according to some embodiments. Load lock modules (modules 603b) may be useful for isolating the conditions created in each process station from their neighboring process stations.

[0106] After proceeding from loading modules 603a through the first load lock module 603b, the mover then proceeds to a third station, according to some embodiments. The third station (comprising modules 603c) is the conditioning station, according to some embodiments. In this station, the product may be subcooled to a designated temperature just below 0°C. This subcooling prepares the product for controlled nucleation, according to some embodiments. For example, the station may be configured to cool the sample to near- or below-freezing temperatures, in order to ensure that it is capable of nucleating solvent crystals without actually initiating uncontrolled nucleation. For example, a plurality of vials disposed on mover 607 may, in some embodiments, be cooled within modules 603c to a designated temperature just below 0°C to prepare the sample for nucleation, according to some embodiments.

[0107] From the conditioning system (comprising modules 603c), mover 607 may proceed to a fourth station, according to some embodiments. The fourth station is the nucleation station (comprising module 603d), according to some embodiments. In this station, controlled30#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 nucleation may occur. For example, in some embodiments, nucleation of solvent crystals (e.g., nucleation of ice crystals in an aqueous sample) occurs in order to initiate the freezing process. Any of a variety of suitable nucleation strategies can be implemented in the nucleation station, including but not limited to vacuum induced surface freezing or thermal quenching. Nucleation may be a relatively fast process, compared with conditioning, and may thus, in some embodiments, take place in a relatively shorter station (e.g., in a station comprising relatively fewer modules). In FIG. 6, for example, the nucleation station comprises a single module 603d. However, it should, of course, be understood that larger nucleation stations may be used, e.g., to increase throughput.

[0108] From the nucleation station (comprising module 603d), mover 607 proceeds to a fifth station, in some embodiments. The fifth process station is the freezing station, comprising modules 603e as shown in FIG. 4, according to some embodiments. In the freezing station, the nucleated samples may be further cooled, e.g., to facilitate growth of nucleated solvent crystals formed in the nucleation system. The growth may be controlled, e.g., by controlling ambient temperature conditions, in order to facilitate homogeneous crystal growth. In the freezing station, the product may be cooled further down to a designated temperature. Any of a variety of designated freezing temperatures may be chosen. For example, in some embodiments the designated freezing temperature is greater than or equal to -70 °C, greater than or equal to -65 °C, greater than or equal to -60 °C, greater than or equal to -55 °C, greater than or equal to -50°C, greater than or equal to -45 °C, greater than or equal to -40 °C, greater than or equal to -35°C, greater than or equal to -30 °C, greater than or equal to -25 °C, greater than or equal to -20°C, greater than or equal to -15 °C, greater than or equal to -10 °C, or greater than or equal to -5°C. In some embodiments, in some embodiments the designated freezing temperature is less than or equal to 0 °C, less than or equal to -5 °C, less than or equal to -10 °C, less than or equal to -15 °C, less than or equal to -20 °C, less than or equal to -25 °C, less than or equal to -30 °C, less than or equal to -35 °C, less than or equal to -40 °C, less than or equal to -45 °C, less than or equal to -50 °C, less than or equal to -55 °C, less than or equal to -60 °C, or less than or equal to -65 °C. Combinations of these ranges are also possible (e.g., greater than or equal to -70 °C and less than or equal to 0 °C, or greater than or equal to -40 °C and less than or equal to -60 °C). Other ranges, both higher and lower than those described above, are also possible, as the31#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 disclosure is not so limited. For example, in some embodiments, the temperature for freezing aqueous samples is between -40 and -60°C.

[0109] This freezing ensures the ice crystals fully solidify and that the product is well below the collapse temperature before entering the drying section, in some embodiments. Like the nucleation and conditioning stations, the length of the freezing station may be chosen to control for the desired throughput. For example, the freezing station may have a length (e.g., may comprise an appropriate number of modules) that depends, in some embodiments, on sample size, sample container, freezing module temperature, and desired throughput, since these factors can affect the freezing rate and / or the time a mover spends in the freezing station.

[0110] From the freezing station (comprising modules 603e), the mover may pass through a load lock module 603b before passing into a sixth process station. The sixth process station is the drying station (comprising modules 603f), according to some embodiments. In this station, the water sublimates out of the product, leaving behind the lyophilized cake, according to some embodiments. Load lock module 603b may act as an airlock, allowing the module to pass from a first pressure of the freezing station modules 603e into a second pressure of the freeze- freeze-drying module 603 f. In some embodiments, the drying station maintains a vacuum environment to drive this sublimation process. The load lock module may be configured to change ambient conditions of the mover from those conditions ambient in the freezing station to those conditions ambient in the drying station, e.g., by reducing the pressure surrounding the mover to a vacuum pressure.

[0111] After passing into the drying station, the movers may be conveyed along the remainder of the course through lyophilization system 601 to another load lock module 603b, to change ambient conditions of the mover to those of the loading station. The mover then returns to position 617b, at the end of the lyophilization pathway, where the fully lyophilized sample may be removed from the mover. The mover then returns to position 617a for reloading and recycling through lyophilization system 601.

[0112] Like the nucleation, conditioning, and freezing stations, the length of the drying station may be chosen to control for the desired throughput. For example, the drying station may have a length (e.g., may comprise an appropriate number of modules) that depends, in some embodiments, on sample size, sample container, freze-drying module temperature, and desired throughput, since these factors can affect the drying rate and / or the time a mover spends in the32#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 drying station. Drying is often, relative to freezing, conditioning, or nucleation, a relatively slow step. Accordingly, in some embodiments such as that of FIG. 6, the drying station is the longest station.

[0113] The lyophilization systems provided herein may use a modular design to make it adjustable to different user needs. The modular nature of the lyophilization system makes it reconfigurable as necessary to optimize its layout, according to some embodiments. This modularity may also help in system development, as the system can be assembled in subassemblies to validate performance.EXAMPLES

[0114] Example 1

[0115] This example describes simulation of cooling chamber performance using unidirectional and bidirectional flow to illustrate the advantages of bidirectional flow. The chamber geometry described with reference to FIG. 4 was used for modeling. The first step in developing the convective cooling chamber for freezing in lyophilization was simulation of the chamber performance given a variety of internal geometry and cooling parameter considerations. Based on the insights provided by the simulation work, the physical chamber was designed to achieve the desired cooling rates.

[0116] Engineering simulation tools were used to model system elements. In a forced convective gas system, the gas needs to move past the surface of the vial on both its bottom and sides. Thus, leaving some space between the vials to permit flow of cooling fluid was considered to be advantageous. The design space for potential vial positions was quite large, and the interactions of the gas flow between multiple vials quickly become too complex for analytical modeling. Simulation therefore serves as a useful tool for validating various layouts of the cooling system.

[0117] FIGS. 7A-7D illustrate the speed of simulated fluid flow at various positions of vial arrangements, while FIG. 7E illustrates the simulated temperature difference between the hottest and the coldest vial for various physical arrangements of vials under unidirectional fluid flow, according to some embodiments. FIG. 7A shows the flow speed of a 3x3 arrangement of lyophilization samples (“3x3” in FIG. 7E). FIG. 7B shows a 3-2-3 arrangement with a wide spacing between the central 2 lyophilization samples(“323 h disp” in FIG. 7E). FIG. 7C shows a33#14406164WGS Ref. M0925.71059WQ00MIT Ref. 261033-2-3 arrangement with a narrow spacing between the central 2 lyophilization samples (“323 hex” in FIG. 7E). FIG. 7D shows lyophilization samples in a 3-2-3 hexagonal layout (“323 h- dist” in FIG. 7E). These simulations show that a hexagonal vial layout provided greater uniformity in temperatures during cooling than a simple grid.

[0118] The second parameter evaluated through simulation was the position of the fluid inlets and outlets. FIGS. 8A-8B illustrate the results of fluid flow simulations based on positioning the gas inlet on the side of the vials (FIG. 8A) or above the vials (FIG. 8B). These simulations showed that the gas inlet positioned above the vials could offer improvements in cooling rate and uniformity. However, further simulations showed that increased gas speed led to the side inlets outperforming the top inlets.

[0119] The third parameter evaluated was the effect of the fluid (in this case, gas) speed. This parameter was shown to have a strong influence on cooling time, as shown in FIG. 9. These results showed that gas speeds above Im / s had diminishing returns in the simulated chamber design (though, of course, other chamber designs could continue to benefit from higher gas flow speeds).

[0120] The fourth parameter to evaluated through simulation was the effect of the inlet height, shown in FIG. 10. These results showed that the inlet height did not have a strong influence on the cooling time or uniformity. Thus, the inlets may be sized and positioned based on the flow generation system without concerns about their effect on the cooling process.

[0121] The fifth parameter to evaluate through simulation was the effect of the cooling strategy on larger geometries. As more rows of units were added to the system, the effectiveness of the selected cooling geometry changed. This effect was be evaluated by doubling the size of the chamber. At the doubled size, the fluid could still have a single inlet on one side of the chamber and an outlet on the other side of the chamber, producing unidirectional fluid flow illustrated by the arrows in FIG. HA. However, the color contrast in FIG. HA, which indicates the fluid speed, varied significantly depending on the position of the vial, resulting in inhomogeneous cooling of samples. An alternative geometry for bidirectional fluid flow with inlets on each side of the chamber and an outlet in the center of the chamber was then simulated for comparison, and the results are shown in FIG. 1 IB. As shown, the bidirectional fluid flow produced by the chamber illustrated in FIG. 4 showed greater uniformity of velocity than the34#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 unidirectional fluid flow illustrated in FIG. HA. This result shows an advantage of the systems and methods provided herein.

[0122] Example 2

[0123] The lyophilization freezing module illustrated in FIG. 4 was constructed and evaluated based on its ability to cool vials quickly and uniformly.

[0124] The cooling of the vials was evaluated. This evaluation was done by placing thermocouples in every vial in the system and measuring its response to the cooling conditions.

[0125] The lyophilization freezing module was evaluated based on the speed at which it cooled vials and the uniformity of the cooling profiles of the vials throughout the system. The uniformity of the freezing system were evaluated at multiple levels. The convective fluid parameter uniformity was measured across various elements of the cooling system as an initial proxy. The first benchmark for uniformity was across the face of one inlet into the chamber. The next benchmark of uniformity was between two sides of the chamber. The final level of uniformity was between different chambers.

[0126] The first uniformity metric was an evaluation of the fluid temperature and speed distribution across the face of a row of muffin fans. This metric ensures that pucks are receiving a uniform temperature exposure regardless of their position on a puck. This uniformity was most strongly influenced by the manifold delivering fresh liquid and gaseous nitrogen into the system. This uniformity was improved by using a manifold with evenly spaced holes, a stainless-steel mesh covering to help disperse liquid nitrogen droplets, and orienting the manifold holes up relative to gravity. This uniformity was most important in an isolated chamber where the vials spend more time in front of the same rows of fans. When multiple chambers were connected together to create a larger system, the vials spent less time in specific locations within the cooling chamber, causing variation in cooling conditions across the inlet face to be averaged out by the vials moving past the face.

[0127] The inlet face uniformity was measured by moving a sensor across the row of fans, generating a fluid flow rate and temperature profile. The temperature is measured using a thermocouple, while the fluid flow rate is measured using a hot wire anemometer. An example set of these parameter profiles appears in FIGS. 12A-12B. This figure showed a variation of temperature less than 1°C and a fluid speed variation of less than 2.5m / s across the face. This level of uniformity was acceptable for the freezing process.35#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0128] The second benchmark of uniformity was the comparison of fluid temperatures and speeds on each side of the system. This uniformity was controlled by adjusting ball valves on the lines which split the fresh nitrogen feed into the ducts on each side of the cooling chamber. Because the chamber was operating at a steady state, the valves were adjusted in that steady state until the desired uniformity is achieved. A plot showing the temperature tracking of two sides of a single chamber is shown in FIGS. 13A-13B. The two sides of the chamber tracked each other within to 0.5°C. The temperature measurement used for generating this plot is taken from the front of the middle fan on the inlets.

[0129] Given the levels of uniformity measured for these two levels, the expected total variation in fluid temperature across all the vials within a chamber is no more than 1.5°C. Given this variation level and a conditioning setpoint of at least 4 degrees below 0°C, all vials were expected to be subcooled to some degree prior to nucleation.

[0130] The third level of uniformity was the comparison of fluid temperatures between different chambers in the system. This uniformity was controlled by a pair of ball valves similarly to the side balancing within the chamber. These ball valves were adjusted once the chambers were in a steady state, where the positions could remain constant because the system operated at constant set points due to its continuous nature.

[0131] Example 3

[0132] Once the chamber uniformity metrics were evaluated, the chamber was then evaluated on how quickly it could cool vials to the predefined setpoints for conditioning and freezing. This test was performed with thermocouples placed in all 20 vials to directly measure their temperature. The presence of thermocouples in the vials was expected to affect the nucleation behavior of the vials because it provides a nucleation site for ice formation to start. However, it did not affect the bulk vial temperature behavior during conditioning and freezing. Each vial had a 3D printed cap with a hole in the top which holds the thermocouple in place, ensuring that it is located within the fluid in the vial without touching the vial walls. The thermocouple wires went through a KF25 port on the rear wall of the test chamber, then through slits cut into a 0.5in plastic tube. A secondary section of the same plastic tube was latched over the thermocouple wire slits to seal these slits, preventing warm atmospheric air from leaking into the chamber and slowing down the cooling process. A picture of this test setup is shown in FIG. 14.36#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0133] This test was performed separately for conditioning and freezing. Due to the isolated nature of the chamber and the wiring used for the thermocouples, the chamber was cooled down along with the vials. Thus, these tests were more like temperature ramp tests than the step change in thermal conditions that vials experience in the actual system. Using the times derived from these experiments for cooling profiles for vials therefore overestimated how long it took for the vial temperature to settle, because the beginning of the cooling process will have a larger gradient. This extra time provided a buffer for the vial temperatures to more confidently reach the chamber temperature setpoint when not actively monitored with thermocouples. The results of the conditioning test with full vial measurement are shown in FIG. 15.

[0134] These results show that the conditioning stage took about 30 minutes from the start of conditioning to the last vial settling at its final temperature. The temperature variation between vials at their settled temperatures was 1 °C. These results matched the expected cooling rate from the prior simulation work, validating the simulations.

[0135] The freezing uniformity experiments use the thermal quench method to nucleate the vials after conditioning. The fluid temperature was rapidly lowered to -30°C for 10 seconds, then raised back up to -10°C for slow ice crystal growth after nucleation. This slow ice crystal growth results in larger ice crystals, which leads to larger pores for drying. The ice crystal growth temperature was held until the vial temperatures start decreasing again from 0°C, which takes about 5 minutes. The chamber setpoint was then lowered to -50°C, and the vials were frozen. The total freezing stage took about 30 minutes from the start of freezing to the last vial settling at its final temperature, which matches the conditioning time because they were both saturating exponential processes. The temperature variation between vials at their settled temperatures is 1 °C. The difference in time between the first and last vials reaching their saturation temperatures was 1 minute. These results also matched the expected cooling rates simulated.

[0136] The above results show that the designed and manufactured cooling chambers can achieve acceptable levels of uniformity to support controlled freezing for lyophilization. This temperature uniformity was particularly advantageous for preparing the vials for nucleation during conditioning. Once this uniformity was validated, the nucleation method tests were performed without concern of variable vial conditions influencing the ability of different methods to successfully induce nucleation at relatively uniform conditions for the vials.37#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103

[0137] The nucleation method tested on this hardware was thermal quench. The convective fluid cooling allowed the vials to experience rapid changes in temperature to create the thermal quench nucleation without adding any additional hardware.

[0138] To prepare for the nucleation tests, the vials were filled with 3mL of water and partially capped. These vials are then placed on a puck and loaded into the cooling chamber. The vials were then supercooled in a chamber with a setpoint of -5 °C for 30 minutes. The nucleation method was then tested. There were two methods for measuring the nucleation methods. The first method used thermocouples in the vials. These thermocouples affected nucleation by serving as ice nucleation sites within the vial. Thus, the results with thermocouples in the vials were not necessarily representative of the nucleation in samples without thermocouples, because the thermocouples made it easier for the solution to nucleate. However, this measurement method provided both nucleation time and temperature, so it could quantify the temperature range over which the vials nucleated. The second measurement method was to optically observe when the vials nucleated and measure the time between seeing the different vials nucleate. The time between first and last observed nucleation from the visual method can then be compared to the results from the thermocouple measurements. If the time between first and last nucleation was similar, then the nucleation temperatures were expected to be similar as well.

[0139] The results from thermal quench testing with thermocouple measurement are shown in FIG. 16A-16B, according to some embodiments. These results show that the vials nucleated within 15 seconds of each other, and the temperature variation between vials at their nucleation point was less than 1°C.

[0140] The thermal quench nucleation thermocouple results were confirmed by the optical tests. During the optical thermal quench nucleation tests, the vials all nucleated within 20s. Given that this time spread approximately matched the results from the thermocouple experiments, the results from the thermocouple experiments were expected to translate to the case where the vials did not include thermocouples.

[0141] The above results show that the cooling chambers can successfully condition, nucleate, and freeze the product in vials with low temperature variation. While the uniformity of cooling conditions can be measured during the freezing process, the evaluation of their effectiveness is shown by drying the product after this freezing process. The resultant total38#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 drying times and variation in drying times provides insight into whether the cooling process provides sufficient uniformity.The embodiments of this disclosure are modular and may be optimized individually and together as a system to realize a forced convection cooling chamber for lyophilization.

[0142] Example 4

[0143] In this example, a cascade controller was used to control the temperature and gas low within the system. FIG. 17 illustrates the measured temperature and flow rate, and compares the fluid temperature to the temperature setpoint set by the controller. This sample simply demonstrates that the cascade controller was capable of maintaining the desired temperature setpoint while the required flow rate changes, as shown in FIG. 17.

[0144] The above method may be implemented by one or more controllers including at least one processor operatively coupled to the various controllable portions of an additive manufacturing system as disclosed herein. The method may be embodied as computer readable instructions stored on non-transitory computer readable memory associated with the at least one processor such that when executed by the at least one processor the additive manufacturing system may perform any of the actions related to the methods disclosed herein. Additionally, it should be understood that the disclosed order of the steps is exemplary and that the disclosed steps may be performed in a different order, simultaneously, and / or may include one or more additional intermediate steps not shown as the disclosure is not so limited.

[0145] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.

[0146] While several embodiments of the present disclosure have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present disclosure. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or39#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 configurations will depend upon the specific application or applications for which the teachings of the present disclosure is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the disclosure described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the disclosure may be practiced otherwise than as specifically described and claimed. The present disclosure is directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the scope of the present disclosure.40#14406164

Claims

WGS Ref. M0925.71059WQ00MIT Ref. 26103CLAIMS1. A lyophilization freezing module comprising: a housing including an internal chamber and a base configured to be disposed on a supporting surface; a passage extending through the housing with a first opening and a second opening configured to permit movement of a lyophilization tray through the passage; a first plurality of fluid flow inlets positioned on a first side of the internal chamber; a second plurality of fluid flow inlets positioned on a second side of the internal chamber opposite from the first side; one or more fluid flow outlets fluidly coupled to internal chamber, the first plurality of fluid flow inlets, and the second plurality of fluid flow inlets; one or more fluid flow actuators configured to create a flow of fluid from the internal chamber through the one or more outlets, through one or more flow passages, and back into the internal chamber through the first plurality of fluid flow inlets and the second plurality of fluid flow inlets; and one or more baffles extending from an upper portion of the internal chamber towards a lower portion of the internal chamber, wherein the one or more baffles are configured to prevent direct flow from the first plurality of fluid flow inlets and the second plurality of fluid flow inlets to the one or more fluid flow outlets.

2. The lyophilization freezing module of claim 1 , wherein the one or more baffles comprise two or more baffles, and wherein the two or more baffles are disposed on opposing sides of the one or more fluid flow outlets.

3. The lyophilization freezing module of any one of the preceding claims, wherein the one or more baffles extend from vertically above to vertically below an upper portion of the first plurality of fluid flow inlets and an upper portion of the second plurality of fluid flow inlets relative to the base.41#14406164WGS Ref. M0925.71059WQ00MIT Ref. 261034. The lyophilization freezing module of any one of the preceding claims, wherein the housing is configured to support a lyophilization tray at a vertical location relative to the base between the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

5. The lyophilization freezing module of any one of the preceding claims, further comprising a cooling fluid source configured to be selectively fluidly coupled to the first plurality of fluid flow inlets and / or the second plurality of fluid flow inlets to flow a cooling fluid into the internal chamber.

6. The lyophilization freezing module of any one of the preceding claims, further comprising a plurality of stators configured to move a magnetic mover through a passage at least partially formed by the internal chamber.

7. The lyophilization freezing module of any one of the preceding claims, wherein the housing is configured to be connected to one or more adjacent housings of one or more adjacent lyophilization modules.

8. The lyophilization freezing module of any one of the preceding claims, further comprising a pressure actuated exhaust port configured to exhaust gas from the internal chamber when a pressure of the internal chamber is greater than a threshold pressure.

9. The lyophilization freezing module of any one of the preceding claims, further comprising a diffuser fluidly coupling the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

10. A method for freezing a material during a lyophilization process, the method comprising: flowing a cooling fluid from a first plurality of fluid flow inlets across a lyophilization tray in a first direction towards a lower opening disposed between one or more baffles extending from an upper portion of an internal chamber the lyophilization tray is disposed in towards a lower portion of the internal chamber;42#14406164WGS Ref. M0925.71059WQ00MIT Ref. 26103 flowing the cooling fluid from a second plurality of fluid flow inlets across the lyophilization tray in a second direction towards the lower opening; directing the cooling fluid towards one or more fluid flow outlets with the one or more baffles; and flowing the cooling fluid from the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

11. The method of claim 10, wherein the one or more baffles comprise two or more baffles, and wherein the two or more baffles are disposed on opposing sides of the one or more fluid flow outlets.

12. The method of any one of claims 10-11, wherein the one or more baffles extend from vertically above to vertically below an upper portion of the first plurality of fluid flow inlets and an upper portion of the second plurality of fluid flow inlets relative to the lyophilization tray.

13. The method of any one of claims 10-12, wherein the method is performed in a housing including a base configured to be disposed on a supporting surface, and wherein the housing is configured to support a lyophilization tray at a vertical location relative to the base between the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

14. The method of any one of claims 10-13, further comprising a cooling fluid source configured to be selectively fluidly coupled to the first plurality of fluid flow inlets and / or the second plurality of fluid flow inlets to flow a cooling fluid into the internal chamber.

15. The method of any one of claims 10-14, further comprising a plurality of stators configured to move a magnetic mover through a passage at least partially formed by the internal chamber.

16. The method of any one of claims 13-15, wherein the housing is connected to one or more adjacent housings of one or more adjacent lyophilization modules.43#14406164WGS Ref. M0925.71059WQ00MIT Ref. 2610317. The method of any one of claims 10-16, further comprising a pressure actuated exhaust port configured to exhaust gas from the internal chamber when a pressure of the internal chamber is greater than a threshold pressure.

18. The method of any one of claims 10-17, further comprising a diffuser fluidly coupling the one or more fluid flow outlets to the first plurality of fluid flow inlets and the second plurality of fluid flow inlets.

19. A lyophilization freezing module comprising: a housing including an internal chamber and a base configured to be disposed on a supporting surface; one or more first fluid flow inlets in fluid communication with the internal chamber; one or more fluid flow outlets fluidly coupled to the internal chamber; a diffuser fluidly coupled to the one or more fluid flow outlets; a first recirculation duct fluidly coupling the diffuser to the one or more fluid flow outlets; and one or more fluid flow actuators configured to create a flow of fluid from the internal chamber through the one or more outlets, through the diffuser, and back into the internal chamber through the one or more fluid flow inlets.

20. The lyophilization freezing module of claim 19, wherein the diffuser, the one or more fluid flow actuators, and the first recirculation duct are mounted to the housing.

21. The lyophilization freezing module of any one of claims 19-20, wherein the first recirculation duct supplies a first recycled portion of the fluid flow to the lyophilization freezing module via a first plurality of inlets of the lyophilization freezing module.

22. The lyophilization freezing module of any one of claims 19-21, further comprising a second recirculation duct.44#14406164WGS Ref. M0925.71059WQ00MIT Ref. 2610323. The lyophilization freezing module of claim 22, wherein the second recirculation duct supplies a second recycled portion of the fluid flow to the lyophilization freezing module via a second plurality of inlets of the lyophilization freezing module.

24. The lyophilization freezing module of any one of claims 19-23, further comprising a manifold configured to supply cryogenic fluid to the first recirculation duct.

25. The lyophilization freezing module of any one of claims 19-24, further comprising a pressure actuated exhaust port configured to exhaust gas from the internal chamber when a pressure of the internal chamber is greater than a threshold pressure.45#14406164

Images