Printed porous structures, methods and apparatus for their production - Patents.com

Abstract

A printed porous structure (500) is fabricated using multi-step absorption, or MSA, the printed porous structure (500) comprising a support layer (520) supporting a filtering membrane (510), the support layer (520) and the filtering membrane (510) being integrally formed.

Description

[Technical field]

[0001] The present invention relates to printing porous structures, more particularly to printing three-dimensional (3D) structures. [Background technology]

[0002] Printing of certain types of porous structures is known, see, for example, U.S. Patent No. 5,399,633, which is incorporated herein by reference in its entirety. Such porous structures can be used, for example, as filter components, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 089421 Summary of the Invention [Problem to be solved by the invention]

[0004] While the filter components produced by the techniques of the '613 patent are a significant improvement over those previously produced, improved techniques for producing complex yet precise porous structures are nevertheless still desired in the art. For example, it would be desirable to improve production speed, reduce costs, have a wider selection of finished materials, structures, etc. [Means for solving the problem]

[0005] Accordingly, there are provided various aspects and embodiments of the invention as defined by the appended claims. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 illustrates a manufacturing apparatus for printing porous structures according to various embodiments of the present invention. [Diagram 2] FIG. 1 illustrates a further manufacturing apparatus for printing porous structures according to various embodiments of the present invention. [Figure 3a] 1A-1D illustrate manufacturing techniques for printing porous structures according to various embodiments of the present invention. [Figure 3b] 1A-1D illustrate manufacturing techniques for printing porous structures according to various embodiments of the present invention. [Figure 3c] 1A-1D illustrate manufacturing techniques for printing porous structures according to various embodiments of the present invention. [Figure 4] FIG. 4 illustrates a variation of the manufacturing technique shown in FIGS. 3a to 3c. [Diagram 5] FIG. 1 illustrates a printed porous structure according to one embodiment of the present invention. [Figure 6] 1A-1D are cross-sectional views of a printed porous structure fabricated using a multi-step absorption (MSA) process according to one embodiment of the present invention. [Figure 7] FIG. 7 is a plan view of the embodiment of FIG. 6. [Figure 8] 1A-1D are top and back views of a PPS made by prior art MSA techniques. [Figure 9] 1A-1D are rear views of a PPS made in accordance with one embodiment of the present invention at two different magnifications. [Figure 10a] FIG. 1 illustrates an ideal gyroid structure. [Figure 10b] FIG. 1 illustrates a gyroid structure fabricated using a conventional MSA process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Various embodiments of the present invention will now be described by way of example only.

[0008] FIG. 1 illustrates a manufacturing apparatus 200 for printing porous structures (PPS) according to various embodiments of the present invention.

[0009] A photon source 202 in the manufacturing apparatus 200 is directed to propagate a beam L of photons towards two electric mirrors 204 and 206, each operable under the influence of a controller 250. The photon source 202 may comprise one or more of a continuous beam laser, a pulsed beam laser, a light emitting diode (LED), a lamp, a discharge tube, a photon emitter, and the like. The photon source 202 may provide coherent photons / beams, partially coherent photons / beams, superluminescent photons / beams, and / or incoherent photons / beams. Such photons / beams may be continuous wave and / or pulsed. The provided photons may include one or more of infrared, near infrared, visible light, and / or ultraviolet photons, and the like. Furthermore, the photons may be of substantially the same wavelength. The photons may be of different wavelengths.

[0010] Again under the influence of the controller 250, one or more adjustable objective lenses 208 are used to focus the beam L to a precise polymerization point P in the vessel 100 for polymerization of a photoactivatable composition provided therein. The photoactivatable composition may be a flowable photoactivatable composition. Photoactivation of the photoactivatable composition by a multi-step absorption (MSA) process causes polymerization therein, which is then used to define a printed porous structure that can be built up, for example, layer by layer.

[0011] By controlled movements of the mirrors 204 and 206, a rapid repositioning of the focal point P can be realized, so that a series of polymerized bits 114 can be written in the shown area A. A layer of bits can be made by adjusting the Z height of the lens 208 using a linear actuator 212 under the control of a controller 250. The vat 100 can also be repositioned in the X axis using a further linear actuator 210, and in the Y axis by a similar arrangement not shown, in each case the actuators being under the influence of the controller 250, so that the neighboring areas B and C, etc. can be polymerized in a similar manner by the mentioned rapid mirror movements, before the neighboring areas are selected. To obtain better accuracy, the space above the vat 100 between the objective lens 208 and the transparent layer 125 (e.g. glass) can be filled with a photon-transparent material 105 (e.g. oil, etc.), so that the photon path L is mainly made of a material having approximately the same refractive index.

[0012] To reduce heating, the photon beam L can be moved larger than the width between adjacent pores (i.e., the inter-pore pitch). The support 220 can also be illuminated separately (e.g., from below) to provide at least one photon in a multi-step absorption (MSA) process.

[0013] Various polymerization methods can be used. For example, a multi-step, preferably two-step absorption (TSA) process using one or more of a two-step absorption method, an optically enabled method, and / or a projection-based manufacturing method can be used. In various embodiments that can be implemented by the controller 250, one or more of the techniques in "Two-step absorption instead of two-photon absorption in 3D nanoprinting", Vincent Hahn et al., Nature Photonics, Vol. 15, December 2021, pp. 932-938, and "Emerging micro-additive manufacturing technologies enabled by novel optical methods", Wei Lin et al., Photonics Research, Vol. 8, No. 12, December 2020, pp. 1827-1842 are used. The contents of both of these documents are further fully incorporated herein by reference in their entirety.

[0014] Other polymerization methods can be used instead or in addition. These can include one or more of multi-beam, interferometric, projection-based, and / or holographic techniques, etc., to photoactivate the photoactivatable composition. In addition to or instead of the polymerization methods, materials with dissolvable particles (e.g., nanoparticles) therein can be used to create the porous and / or wall structures that function as at least a portion of the porous structure (PPS).

[0015] Regardless of which polymerization method is used, successive buildups of polymerized material can introduce problems of reduced transparency and diffraction. To reduce these problems, the fabrication apparatus 200 can further optionally utilize accurate modeling of the underlying 3D structure by evaluating and optimizing localized photon dose, angle, etc., and energy application to account for non-uniformities, diffraction patterns, etc. within the structure.

[0016] Thus, a variety of printed porous structures (PPS) can be produced using the multi-step absorption (MSA) process in the production apparatus 200. Examples of such PPS include at least one of filters, sieves, meshes, membranes, scaffolds, frames, lattices, and / or networks. Such PPS can include, for example, woodpile, diamond lattice, body-centered cubic (BCC), and / or gyroid structures, optionally having monofocal, bifocal, and / or trifocal, etc. Optionally, the production of PPS can also further include removal of any unpolymerized composition and / or embedded particles (e.g., by vacuum suction, dissolving with a solvent, etc.) to leave open pores in the printed porous structure.

[0017] In various embodiments, the printed porous structure can include a plurality of substantially similarly sized pores therein. The pores therein can have a size of about 15 μm, 10 μm, 5 μm, 3 μm, 1 μm, 500 nm, and / or 100 nm, and any intermediate size therein. The pore-to-pore distance (pitch) can be about 10 μm or less.

[0018] Printed porous structures of various dimensions can also be produced depending on the desired end use. For example, PPS having a surface diameter (Φ) of about 13 mm or about 25 mm or less can be achieved. 2 to a maximum of at least about 1 mm 2 , 10mm 2 , 1cm 2 , or 4~5cm 2 A treatment area of ​​about 5 μm, 10 μm, or 20 μm, a thickness (z) of at least about 30 μm, at least about 50 μm, or at least about 100 μm can also be achieved.

[0019] Further PPS may be manufactured with at least one region that is substantially free of pores (e.g., to provide a reinforcing ring-like support). Additionally or alternatively, filter devices and holders therefor may be produced that include any of the above-mentioned claimed printed porous structures (PPS). Such holders may optionally be integrally formed with said PPS.

[0020] Many types of materials can also be used to manufacture PPS, including, but not limited to, one or more / multi- or hybrid / composite of polyimide, polyethylene, polycarbonate, polypropylene, acrylate, methacrylate, urethane, PEG (polyethylene glycol)-based, PLA (polylactic acid)-based, protein-based (e.g., albumin, collagen, fibrinogen), and / or thiol-ene materials, optionally in low viscosity fluid, high viscosity fluid, or solid form. Such materials can also be mixed with at least one photoinitiator, optionally including water soluble, and possible doping materials, such as metals, ceramics, nanoparticles or nanotubes, hydrogels, and / or shape memory polymers.

[0021] FIG. 2 shows a further manufacturing apparatus 200' for printing porous structures according to various embodiments of the present invention.

[0022] While the manufacturing apparatus 200 of Figure 1 can provide sufficiently fast PPS generation, faster generation may be desired, thus providing for the use of multiple photon beams L as shown in Figure 2. Multiple photon sources 211 are provided, which may be generated by splitting one or more photon beams into many beams, for example using multiple beam splitters. The latter approach is less expensive but requires more beam alignment, so multiple photon sources 211 may be preferred.

[0023] The manufacturing apparatus 200' shown in Figure 2 operates in a similar manner to that described above with reference to Figure 1, except that multiple photon sources 211 are grouped together and their output beams are formed into a converging pattern (in this case, nine photon sources arranged in a 3 x 3 two-dimensional pattern). The photon beams propagate towards a bath of polymer composition 100 as explained above, and can be moved in stages to form polymerized bits as detailed above.

[0024] The photon beams L' may be spaced apart by more than one hole pitch (e.g., to reduce heat generation), so for example, if the beams L' are spaced apart by X pitches, except for the end holes, and then moved in steps by X-1 pitches, the remaining holes can be formed with less heat generation than by moving just one pitch at a time.

[0025] 3a to 3c illustrate a manufacturing technique for printing porous structures according to various embodiments of the present invention.

[0026] Referring to FIG. 3a, an example of a production technique is shown diagrammatically. Shown in cross section is a portion of a bath of liquid composition 100, including a silicone rubber substrate bed 220. The composition includes at least a mixture of photoactivatable monomer molecules, photoactivatable initiator molecules, and photoactivatable quencher molecules, as described below. In this figure, a linear series of bits 114 of polymerized composition 100 are formed using a photon beam L, focused at a constant bit height in the Z axis. The focus is aligned to the desired X and Y axis coordinates. Z is up and down the page of the figure, X is left and right of the figure, and Y is into and out of the figure. Such a beam forms overlapping polymerized bits 114, but control of the beam is used to leave unpolymerized "holes" 112. This can be achieved, for example, by gating the beam and / or using a pulsed photon beam.

[0027] The photon beam is then optically repositioned to an adjacent location to repeat the solidification of the next series of bits 114. In the figure, the beam focus P is scanned (left to right) to X and periodically energized to produce a series of bits 114, but not at the locations where holes 112 are intended to be located.

[0028] In Figure 3b, a second layer of polymerized bits is created by rescanning the focus P, in this case with the same pattern as in Figure 3a, but with a height Z raised by less than one bit size to overlap with the first series of bits, but also allowing an unenergized scan of the beam over the hole area 112, slightly overlapping the first layer shown in Figure 3a. Such layer-by-layer polymerization can then be repeated many times to create a porous structure with almost any hole size and hole pattern at a desired thickness.

[0029] FIG. 3c shows the final printed porous structure 140 formed by a further layer of bits formed on top of the previous layer with unpolymerized pore areas 112. In reality, those pore areas 112 are emptied of unpolymerized composition, for example by washing the printed porous structure 140 with a solvent. For clarity, the bits are shown much larger than they would be when actually formed. The interstitial areas 118 formed between the ends 120 of the pore areas 112 are shown polymerized. However, it is within the scope of the present invention to leave at least a portion of those interstitial areas 118 unpolymerized and to perform a high degree of final polymerization once the pore areas 112 are washed away, whereby the areas 118 are also polymerized. In various embodiments, the polymerized material is selected to be easily sterilizable, for example by gamma radiation.

[0030] For convenience, the pore area 112 is shown as a simple vertical pore path, but it is equally easy to generate other shapes of pore paths, e.g., helical pores, zigzag pores, pseudo-random paths, etc., which may in fact be better shaped to retain or capture analytes of interest, e.g., larger molecules such as proteins or cells, while allowing others to pass through the PPS. Such circuitous paths may be provided, for example, for depth filtering.

[0031] The pore diameter may be, for example, less than 5 μm or more, with a typical pore path length (not necessarily the thickness of the PPS) of, for example, 5, 10, 20, 50, or 100 times the pore diameter. For tall pores with relatively small diameters, if only the pore ends 120 are polymerized while the area 118′ is still liquid, the tall hollow structure may be relatively weak once the liquid in the pore area 112 is washed away. It is then possible to strengthen those solidified ends 120, for example by polymerizing the fasteners 121 joining the adjacent ends 120 of adjacent pore areas 112. Multiple fasteners between the pore ends 120, for example cross fasteners 121 as shown in FIG. 3b and FIG. 3c, may also be employed to improve strength and stiffness.

[0032] Figure 4 shows a variation of the manufacturing technique shown in Figures 3a to 3c. In this embodiment, a male mold with an artefact 312 is formed by photopolymerisation using the same technique as described above. The unpolymerised remains of the polymer 318 are washed away leaving the male mold, and the now voids 318 can be filled with a film-forming material such as a filled thermosetting polymer. Once the filled polymer is in place, the mold can be removed mechanically, or by washing with a suitable solvent, or by heat, leaving a hole.

[0033] In various embodiments, the flowable composition 100 includes a transparent photoactivatable acrylate monomer resin doped with up to 3% of a photoactive initiator, such as a 2,4,6-trimethylbenzoyldiphenylphosphine oxide molecule, or an acylphosphine oxide, such as a benzophenone, a xanthone, or a quinone, or a combination of these molecules, and a photoactive quencher, such as a tertiary amine molecule. The photon beam can be provided, for example, by an exciplex laser (also known as an excimer laser) having an output wavelength of about 800 nm, with a pulse length of about 10 fs to 100 fs, such as about 40 femtoseconds (fs) to 60 femtoseconds (fs) (e.g., about 50 fs may be preferred), optionally with a repetition rate of about 5 MHz.

[0034] Furthermore, while the holes are the primary dimensional focus, the gaps between the holes can be filled with less resolution, for example, by using a higher energy photon beam, where possible, to photopolymerize larger areas more quickly and thereby speed up the manufacturing process, or by the introduction of material by jetting, for example the introduction of a liquid thermoplastic, although it does not necessarily have to be the same material as that surrounding the holes.

[0035] The energy required to bring about localized polymerization can be provided by a focused photon beam in at least one focal point in the composition 100 by two-photon absorption polymerization. That is, two or more photons are simultaneously absorbed by a photoactive initiator (photoinitiator) to create an activated chemical species that initiates the polymerization of the monomer resin. Under these conditions, multiphoton absorption occurs only in the area where the intensity is highest. This limits the polymerization within the volume (known as a voxel) of the focused photon beam. Small overlapping bits (e.g., 25% overlapping) of polymerized material can thus be generated. Quenching molecules can also achieve quenching of fluorescence to inhibit or stop the dendritic unfolding of the polymer branches. This can then achieve a more tightly defined polymerization volume. The printed porous structure can be further revealed by washing away the unsolidified parts of the resin using an organic solvent.

[0036] FIG. 5 shows a printed porous structure 10' according to one embodiment of the present invention. The printed porous structure 10' includes fibers 411, e.g., nanofibers, introduced into the composition bath 100 during manufacture, which do not unduly interfere with the formation of the pores described above. This improves the mechanical strength of the finished printed porous structure 10'. Additionally or alternatively, a mesh or netting material (not shown) having a relatively coarse weave compared to the size and location of the pores can be immersed in the bath 100 prior to polymerization to achieve the same effect. Once the pores are formed, the mesh or the like is incorporated into the printed porous structure 10', again adding significant strength, thereby allowing for a higher transmembrane pressure difference during use.

[0037] The mentioned substrate support 220 is intended in the above examples to be a removable surface on which the porous structure is formed. In addition, the substrate support 220 surface can be optionally adapted to mount thereon one or more microsensors 400 and, if necessary, conductive paths 410 for communication and / or power supply between such sensors 400. These can be formed on the surface of the support 220 before the polymer bath is presented, for example by 3D printing. By peeling the support 220 from the finished porous structure or vice versa, the sensors and any conductive tracks remain in place, ready for use on or in the finished porous structure.

[0038] In this case, the microsensor 400 may be a capacitive interstitial sensor that measures transmembrane pressure differential, which can provide an indication of the filter performance of the PPS. Other sensors can be used, such as, for example, other pressure sensors, flow sensors, conductivity sensors, pH sensors, osmolality sensors, chemical composition or concentration sensors, etc., that can provide data in real time as the filtering process occurs, for example to measure the performance of the porous structure.

[0039] In another example (not shown), a porous structure can be formed on a substrate, the substrate including an absorbance sensor, the porous structure including an inlet and an outlet to the sensor, so that the absorbance properties of the fluid passing through the porous structure can be monitored remotely. This can monitor the concentration of proteins, etc. In yet another variation, the porous structure can be formed over a microfluidic valve and a pressure sensor, which can generate a signal to open a valve, for example, when the pressure difference between the two sides exceeds a predefined amount. Other sensors can also be used, such as, for example, a conductivity sensor when there is an interruption in the electrical path, for example, when a broken porous structure signals a failure of the porous structure, or temperature sensing can be used. The use of more conventional additive manufacturing of low-resolution materials to generate additional sensors or other accessories of the porous structure or filter device, such as, for example, a frame or other physical support, can be combined with the porous structure manufacturing methods described herein.

[0040] Although the illustrated embodiments provide a generally planar / plate-like porous structure, the porous structure may be useful in other geometries, for example, tubular membranes acting as hollow fibers in hollow fiber filtration processes.

[0041] Using the techniques described above, asymmetric features can be achieved in a single porous structure layer, and can even have multiple asymmetries in physical properties (e.g., wider then narrower then wider pores) and / or contoured surface properties that promote surface or depth filtering, such as funnel-shaped or constricted pore openings. For example, a gyroid lattice can be provided as a single volume version. However, a gyroid lattice can also be produced as a two-volume version, with two regions separated by a wall. This latter embodiment is particularly useful for producing heat exchangers, and can also be used to facilitate cell replacement.

[0042] Chemical ligands or anchors for subsequent ligand attachment can be printed to allow control of placement and subsequent modification of anisotropic and asymmetric properties for improved function and / or more efficient use of (expensive) ligands.

[0043] Additionally, in one embodiment, a light conduit or light guide may be included. Such a light guide may allow for a secondary polymerization step inside a structure that has, for example, poor transmission. If the light has a terminal light diffuser or lens, the light guided into the structure to a partially polymerized porous structure may be used to fully polymerize the porous structure.

[0044] Although the production of the porous structure in individual sheets has been described and illustrated, it will be apparent that other techniques can be employed, for example, continuous manufacturing techniques can be used, for example, the finished porous structure can be stripped of its support 220, washed to produce pores, and then wound onto a roll.

[0045] The MSA / TSA process can thus be used to generate reduced size PPSs at the millimeter or sub-millimeter scale (e.g., d=2.0 mm and h=0.07 mm) or full size PPSs (e.g., d=9.5 mm and h=0.07 mm) by applying, for example, up to five iterations. In various embodiments, the highest applied print resolution may be applied, i.e., slice distance in z direction: 0.5 μm, hatch distance in x / y direction: 0.5 μm. For certain embodiments, parallel manufacturing of PPSs (e.g., with implementation of one DOE-optical diffractive element) can be realized and / or a line spacing of 7.15 μm can be used.

[0046] Optionally, a holder can be provided to accommodate such a PPS, which can also be produced using the MSA / TSA process. For example, a holder can be provided having a diameter d=13.0 mm or d=25.0 mm and a height of at least 30 μm.

[0047] A variety of other filters can also be made that have one or more of the following characteristics:

[0048] [Table 1]

[0049] [Table 2]

[0050] PPS can be formed of one or more of the following photopolymerizable materials: acrylate, methacrylate, urethane, PEG (polyethylene glycol)-based, PLA (polylactic acid)-based, protein-based (e.g., albumin, collagen, fibrinogen), and / or thiol-ene materials. These materials can be mixed with a photoinitiator. Materials such as polyimide, polyethylene, polycarbonate, and / or polypropylene can alternatively or additionally be microdrilled (e.g., using a laser, etc.) and can optionally be about 10 μm thick. Microdrills can be used to provide holes with an exit diameter of 2 μm±0.5 μm. In various embodiments, an inlet diameter of the holes of about 7 μm is provided. The treated areas of the porous structure can be up to at least about 1 cm in areas having a hole-to-hole distance (pitch) of about 10 μm or less. 2 Such printed porous structures can thus be used in microfiltration applications.

[0051] FIG. 6 shows a cross-sectional view of a printed porous structure 500 fabricated using a multi-step absorption (MSA) process according to one embodiment of the present invention.

[0052] Printed porous structure (PPS) 500 comprises a support layer 520 that supports a filtering membrane 510. The support layer 520 and filtering membrane 510 are integrally formed together on a substrate 540. More specifically, the support layer 520 and filtering membrane 510 are not constructed as separate pieces and later physically joined together (e.g., by gluing, welding, heat fusing, etc.), but rather are made together as part of the same manufacturing process.

[0053] Both the support layer 520 and the filtering membrane 510 are built sequentially on top of the substrate using the MSA process. The support layer 520 provides a scaffolding that prevents any part of the filtering membrane 510 from contacting the substrate 540 during the formation of the PPS by providing a gap between the filtering membrane 510 and the substrate 540 in the Z offset direction. The size of the gap required can be determined according to the properties of the materials used and the size, shape, and dimensions of the structures of the support layer 520 and / or filtering membrane 510.

[0054] In various embodiments, the support layer 520 and the filtering membrane 510 can be integrally formed from the same material. For example, an acrylate resin material can be used on a glass substrate. In this embodiment, the support layer 520 also preferably includes a wide substrate contact 530 that is first formed adjacent to the substrate 540. Such a shape helps prevent the bottom or back portion of the filtering membrane 510 formed close to the substrate 540 from blocking the holes. In various embodiments, the substrate contact 530 can be about twice as wide at the contact with the substrate 540 as compared to the top or main structure portion of the support layer 520.

[0055] The filtering membrane 510 is then integrally constructed with a support layer 520 to provide channels therein having gyroid structures with a substantially triply periodic minimal surface (TPMS) shape. For example, the TPMS may be of a diamond TPMS shape. Once the final three-dimensional PPS 500 is formed on the substrate 540, it can be removed therefrom (e.g., by physical and / or chemically assisted peeling of the PPS 500 from the substrate 540).

[0056] FIG. 7 shows a plan view of an embodiment of the printed porous structure (PPS) 500 of FIG. 6. As can be seen from FIG. 7, the scaffold realized by the support layer 520 is substantially lattice-shaped. In this case, the lattice forms a square / rectangular pattern, and the areas within the lattice are effectively filled with filtering membrane 510 portions having respective holes / channels 550 therein. While in this case, the lattice pattern is square / rectangular, it will be understood that various alternative embodiments can be realized. For example, one or more hexagonal, octagonal, etc. shaped pattern portions can be used as desired. Furthermore, irregular and / or mixed shaped lattice patterns can also be provided.

[0057] In this embodiment, the grid spacing of the scaffold is substantially equal to the size of the field of view of the objective lens used during the MSA process. This realizes the advantage that stitch lines between adjacent sequentially manufactured areas, which may occur as an artifact of the MSA process, can be re-forced by the scaffold. This both strengthens the stitch lines and also allows the PPS 500 to be more easily lifted off the substrate 540.

[0058] Thus, the lattice may be provided by boundary walls that extend substantially in the Z-offset direction. Typical Z-offset (spacing) values ​​are between 2.5 μm and 10 μm, and typical lattice spacing XY dimension values ​​are between 9 μm and 53 μm for pore sizes between 1 μm and 3 μm. Various dimensions that affect the essential MSA process parameters required for a given pore size were found to include lattice spacing, Z-offset, and membrane size. Parameters found to be less critical included laser power, membrane thickness, membrane material type, pore size, and mesh type (gyroid, woodpile, etc.).

[0059] FIG. 8 shows a top 614' and back 612' view of PPS made by the prior art MSA technique. The membrane was formed from an acrylate resin material on a glass substrate. FIGS. 612', 614' were obtained using a Scanning Electron Microscope (SEM). The MSA PPS membranes were made with both 1 μm and 3 μm pore sizes.

[0060] The top view 614' shows that an acceptable top membrane structure pattern having a gyroid channel shape can be produced. However, the back view 612' shows that the desired top pattern is not repeated for the surface fabricated closest to the substrate used during the MSA process. The reasons for this are further outlined below in relation to Figures 10a and 10b.

[0061] FIG. 9 shows the back view of PPS500 made using the MSA process according to an embodiment of the present invention at two different magnifications. The views of PPS500 were obtained using a scanning electron microscope (SEM). PPS500 was made using an acrylate resin material formed on a glass substrate with a grid size of 26.5 μm×26.5 μm. The membrane size was 13 mm (outer diameter) and 9 mm (inner diameter). The Z-offset used was 10 μm and the filtering membrane had a thickness of 30 μm. The channel structure in the filtering membrane was of a gyroid TPMS shape with a pore size of 3 μm.

[0062] Both figures in FIG. 9 clearly show that acceptable submembrane structure patterns were produced having well-defined, substantially ideal gyroid-shaped channels therein.

[0063] FIG. 10a shows an ideal gyroid structure 610, and FIG. 10b shows a gyroid structure 610' fabricated using a conventional MSA process.

[0064] 10a depicts an idealized gyroid structure 610 in which a gyroid-shaped pathway of substantially constant cross section is provided between an upper surface 614 and a lower surface 612. Gyroid structures (e.g., having a TPMS shape) are useful because they provide good structural support, intricate pathways, reduce the chance of channel blockage by providing multiple through pathways, etc. Gyroid structures can also be used to help reduce or eliminate most variations in surface pressure across at least a portion of the filtering membrane 510.

[0065] In practice, however, when a conventional gyroid structure is fabricated on a substrate, various defects arise therein, as shown in FIG. 10b. This is because the interface between the printed mesh and the substrate resin can be blurred on the substrate, thereby closing the holes on the bottom side 612'. Depending on the geometry used, this can result in a thin line effect or an almost completely plugged mesh. In addition, gyroid structures often have a fillet-like peripheral attachment to the substrate that also closes the holes on the substrate side.

[0066] Various embodiments produced using MSA / TSA techniques can thus be realized. Advantageously, the printing speed for these may also be increased compared to conventional methods without compromising resolution. In addition, such an approach also results in reduced manufacturing costs due to the use of less powerful light sources / beams, reduced use of printing materials / inks / photoinitiators, etc., and a larger production volume (print unit) per comparable time frame. Furthermore, greater freedom in the selection of printing materials is possible, resulting in a wider range of final compositions for the final printed product.

[0067] Various embodiments of the present invention can thus further provide free-standing (macrometric) structures that can be easily released after fabrication. Such structures can provide improved, substantially unrestricted flow path structures, for example, compared to prior art MSA fabricated products that require polishing / cutting the device from the substrate after fabrication, etc. Furthermore, the design of the flow paths within such structures can be precisely controlled to achieve desired fluid flow structures (e.g., a substantially constant fluid flow shape across the surface of the PPS, or a PPS having a desired localized fluid flow shape therein).

[0068] While a number of embodiments have been described and illustrated, it will be apparent to those skilled in the art that additions, omissions, and modifications can be made to these embodiments without departing from the scope of the invention as claimed. [Explanation of symbols]

[0069] 10' Printed Porous Structure 100 Composition, composition tank, tank, polymer composition, polymeric composition, liquid composition, flowable composition 105 Photon transmission materials 112 Hole area, hole 114 bits, multiple bits 118 Gap Area 118' area 120 End 121 Fasteners 125 Transparent layer 140 Printed Porous Structure 200 Manufacturing equipment, equipment 200' manufacturing equipment 202 Photon Source 204 Electric reflector 206 Electric reflector 208 Objective Lens 210 Linear Actuator 211 Photon Source 212 Linear Actuator 220 Substrate support, silicone rubber substrate floor 250 Controller 312 Artifacts 318 Unpolymerized remainder, void 400 Microsensor 410 Conductive Path 411 Textiles 500 Printed Porous Structure, PPS 510 Filtering Membrane 520 Supporter layer 530 Board contact part 540 Substrate 550 holes 610 Ideal Gyroid Structure 610' Gyroid Structure 612 Bottom surface 612' Rear view, bottom side 614 Top surface 614' Top view

Claims

1. 1. A printed porous structure (PPS) (500) manufactured using a multi-step absorption (MSA) process, the printed porous structure (500) comprising a support layer (520) supporting a filtering membrane (510), the support layer (520) and the filtering membrane (510) being integrally formed.

2. 2. The printed porous structure (PPS) (500) of claim 1, wherein the support layer (520) provides a scaffolding that prevents the filtering membrane (510) from contacting a substrate (540) on which the printed porous structure (PPS) (500) is formed.

3. The printed porous structure (PPS) (500) of claim 2, wherein the scaffold is in the shape of a lattice.

4. 4. The printed porous structure (PPS) (500) of claim 3, wherein the lattice spacing of the scaffold is substantially equal to the size of the field of view of an objective lens (208) used during the multi-step absorption (MSA) process.

5. The printed porous structure (PPS) (500) according to any one of claims 1 to 4, wherein the multi-step absorption (MSA) process uses one or more of a multi-step, preferably two-step absorption (TSA) method, an optically enabled method, and / or a projection-based manufacturing method.

6. 6. The printed porous structure (PPS) (500) of any one of claims 1 to 5, wherein the filtering membrane comprises a woodpile, diamond lattice, body-centered cubic (BCC), and / or gyroid structure, optionally with a single focus, two foci, and / or three foci.

7. The printed porous structure (PPS) (500) of claim 6, wherein the filtering membrane (510) comprises at least one gyroid structure.

8. 8. The printed porous structure (PPS) (500) of claim 7, wherein the at least one gyroid structure comprises a TPMS structure.

9. 9. The printed porous structure (PPS) (500) of any one of claims 1 to 8, comprising a plurality of holes (550) of substantially similar size therein.

10. 10. The printed porous structure (PPS) (500) of any one of claims 1 to 9, wherein the plurality of pores (550) therein have a size of about 15 μm, 10 μm, 5 μm, 3 μm, 1 μm, 500 nm, and / or 100 nm, and any intermediate size therein.

11. 11. The printed porous structure (PPS) (500) of any one of claims 1 to 10, having a pore-to-pore distance (pitch) of about 10 μm or less.

12. 12. The printed porous structure (PPS) (500) according to any one of claims 1 to 11, having a surface diameter (Φ) therein of about 13 mm or about 25 mm or less.

13. 13. The printed porous structure (PPS) (500) of any one of claims 1 to 12, having a thickness (z) of about 5 μm, 10 μm, or 20 μm, at least about 30 μm, at least about 50 μm, or at least about 100 μm.

14. 14. The printed porous structure (PPS) (500) of any one of claims 1 to 13, further comprising at least one area that is substantially free of pores.

15. At least about 0.5 mm ２ to a maximum of at least about 1 mm ２ , 10 mm ２ , 1 cm ２ , or 4 cm ２ ~5cm ２ 15. The printed porous structure (PPS) (500) of any one of claims 1 to 14, further comprising at least one treated area of:

16. The printed porous structure (PPS) (500) according to any one of claims 1 to 15, wherein the material comprises one or more of polyimide, polyethylene, polycarbonate, polypropylene, acrylate, methacrylate, urethane, PEG (polyethylene glycol) based, PLA (polylactic acid) based, protein based (e.g. albumin, collagen, fibrinogen), or thiol-ene materials, optionally in the form of a low viscosity fluid, a high viscosity fluid, or a solid.

17. The printed porous structure (PPS) (500) of claim 16, wherein the material is mixed with at least one photoinitiator, optionally with water solubility, and possible doping materials, such as metals, ceramics, nanoparticles or nanotubes, hydrogels, and / or shape memory polymers.

18. 18. The printed porous structure (PPS) (500) of any one of claims 1 to 17, wherein the support layer (520) and the filtering membrane (510) are integrally formed from the same material.

19. A printed porous structure (PPS) (500) according to any one of claims 1 to 18, a holder for said printed porous structure (PPS) (500); A filter device comprising: A filter device, wherein said holder is also optionally integrally formed with said printed porous structure (PPS).

20. A method for the production of a printed porous structure (PPS) (500) according to any one of claims 1 to 18 or a filter device according to claim 19, comprising: (a) providing a photoactivatable composition; (b) photoactivating the photoactivatable composition to define the printed porous structure; A method comprising:

21. The method of claim 20 , wherein the photoactivatable composition is a flowable photoactivatable composition.

22. 22. The method of claim 20 or 21, wherein the step of photoactivating the photoactivatable composition to define the printed porous structure (500) comprises sequentially activating the photoactivatable composition at a plurality of different locations to form the printed porous structure.

23. (i) providing at least one focal point in said photoactivatable composition with photons of sufficient energy to locally polymerize said composition; (ii) moving the or each focal point to a number of further positions in a sequential or stepwise predefined manner relative to the previously polymerized composition; (iii) repeating steps (i) and (ii) so that the three-dimensional matrix of said composition is polymerized, leaving unpolymerized areas corresponding to the plurality of pores (550) of the printed porous structure; 23. The method of claim 22, comprising:

24. 24. The method of any one of claims 20 to 23, wherein the step of photoactivating the composition to define the printed porous structure comprises irradiating the photoactivatable composition with one or more of infrared, near infrared, visible, and / or ultraviolet photons.

25. 25. The method of claim 24, wherein at least two photons photoactivate the photoactivatable composition.

26. 26. The method of any one of claims 20 to 25, wherein the photons are provided by one or more of a continuous beam laser, a pulsed beam laser, a light emitting diode (LED), a lamp, a discharge tube, and a photon emitter.

27. 27. The method of any one of claims 20 to 26, further comprising the steps of: (i) removing unpolymerized composition to leave open pores (550) in the printed porous structure (500); and / or (ii) producing the printed porous structure (500) or the filter device on a substrate (540) and removing the printed porous structure or the filter device from the substrate (540) once it has been produced.

28. 28. The method of any one of claims 20 to 27, comprising using one or more of multi-beam, interferometric, projection-based, and / or holographic techniques to photoactivate the photoactivatable composition.

29. An apparatus (200) for producing a printed porous structure (500), the apparatus (200) being operable to perform the method according to any one of claims 20 to 28.

Images