Fabrication process for lab-on-a-chip

Abstract

A lab-on-chip and a method for its layered manufacturing, wherein the method comprises: programming by computer the printed circuit (7), the mixing and reaction chambers (3), the microchannels (2) and the spaces (15) for placing electronic components to be provided in each layer; machining in one or more biocompatible substrates the different voids and channels that will constitute the mixing and reaction chambers (3), the microchannels (2), the holes (8) connecting the microchannels and the spaces (15) for placing electronic components later; metallizing the surfaces where the printed circuit (7) is to be integrated according to the programming made in the first step with a biocompatible conductive material; producing the printed circuit (7) by means of photolithography and acid attack; gluing the electronic components in the corresponding spaces (15); connecting all the layers that constitute the final lab.

Description

Technical Field

[0001] This invention belongs to the field of laboratory-on-chip (i.e., lab-on-chip) integrated on a chip.

[0002] This invention has applications in fields such as hygiene, veterinary medicine, industry, chemistry, environment, agri-food, and pharmaceuticals. It can be used in PCR (polymerase chain reaction) devices (i.e., DNA analysis, parameter analysis systems, portable or non-portable, for example, targeting creatinine or tumor markers), for measuring pH in fluids, for performing gas or contaminant sensing, for manufacturing reaction devices or digester devices, for detecting compounds in food (e.g., volatile compounds in olive oil), or for producing and testing pharmaceuticals. Background Technology

[0003] Lab-on-a-Chip technology is booming due to its potential applications in various fields such as pharmaceuticals and agri-food. One of the most interesting applications of these technologies is the fabrication of miniaturized conventional analytical systems. This application offers several improvements compared to conventional systems, such as: reducing the amount of reagents required and a significant portion of the cost of current analyses; automating the process using connected electronics that influence the process by selecting when each step occurs and reading the results once the process is complete; making analysis faster due to the reduced amount of fluids involved in the process; making the entire system portable, allowing analysis to be performed where electrical connections are not possible; and reducing the overall cost of the process due to all the aforementioned improvements.

[0004] In the future, these technologies could potentially replace traditional analytical systems, such as those used in clinical or food analysis laboratories, reducing analytical costs by orders of magnitude. This would also eliminate the need for medical teams to make secondary visits to patients to retrieve results.

[0005] There are still unresolved issues in manufacturing this type of device due to the high cost of the materials and manufacturing processes used. These processes are slow, difficult to industrialize, and do not allow for continuous manufacturing. Summary of the Invention

[0006] This invention includes a rapid, more economical, and easily reproducible manufacturing method in which a lab-on-a-chip comprises continuous layers of biocompatible material. These biocompatible material layers integrate printed electronic circuitry within biocompatible conductive material between the layers. This circuitry connects actuators and sensors designed into or embedded in the electronic circuitry itself. This circuitry is combined with a three-dimensional microchannel system that runs through the layers or intersects with various types of structures (e.g., measurement chambers, filters, decanters, etc.) designed for desired analytical functions. The microchannels are connected to chambers for introducing fluids (e.g., chemical reagents or samples), which are driven by electronically controlled bidirectional pistons. The printed electronic circuitry has external connections to other external electronic components or systems and can be used to provide, control, or interpret signals from the chip.

[0007] To address the technical challenges necessary to manufacture such chips, a layered manufacturing process has been designed in which all layers are made of biocompatible materials, such as, but not limited to, PMMA (polymethyl methacrylate), COC, polycarbonate, silicon, etc.

[0008] This manufacturing process involves metallizing the surfaces of biocompatible materials on which biocompatible printed electronic circuits are to be integrated. Metallization is achieved by adhering a pre-formed metal layer to a biocompatible substrate using resin. After creating a track pattern in the metal using photolithography, the resin is removed, leaving the surface in contact with the liquid or sample made of either the biocompatible polymer or the metal. In this way, a metallized biocompatible substrate is realized, where printed circuits can be fabricated using conventional methods, and active electronic components can be added within the biocompatible structure without the need for expensive metals or highly specialized manufacturing methods.

[0009] Microchannels or pores are sculpted, cut, drilled, or imprinted (e.g., by laser) in different layers of biocompatible materials. Once different layers or substrates of a polymer are bonded together, they form microchannels that house electronic components, constitute a drive system, or define the physical spacing of each region of a chip.

[0010] Similar to printed electronic circuits, the lab also includes electronic sensors and actuators embedded in the layers of the device. Sensors measure physical parameters such as temperature, pH, and luminescence, and are connected to mechanical drive systems and electronic boards. The data recorded by the sensors is processed and interpreted in a processor. In this way, control of test conditions within the chip can be performed, parameters such as temperature can be measured and manipulated, or operations can be performed within the analysis process via, for example, light emitters or receivers. Because fluid contact with the metal layers always occurs at points specifically designed for this purpose, non-biocompatible electronic components can be isolated within watertight cavities and connected via conductive layers. Attached Figure Description

[0011] To supplement the description and to help better understand the features of the invention, a set of drawings is included as part of the description, wherein the following drawings are provided by way of illustration rather than limitation.

[0012] Figure 1 This is a floor plan of a lab-on-a-chip according to the present invention.

[0013] Figure 2 This is a three-dimensional view of the laboratory according to the present invention.

[0014] Figure 3 A plan view [A] and a cross-sectional view [B] of the lab-on-a-chip of the present invention are shown.

[0015] Figure 4 yes Figure 3 A cross-sectional view of the manufacturing process of the upper layer of the microfluidic chip.

[0016] Figure 5 yes Figure 3 A cross-sectional view of the manufacturing process of the intermediate layer of a microfluidic chip.

[0017] Figure 6 yes Figure 3 A cross-sectional view of the manufacturing process of the lower layer of the microfluidic chip.

[0018] Figure 7 This is a cross-sectional view of the process used to bond the upper layer [A], the middle layer [B], and the lower layer [C] to form a complete microfluidic chip [D]. Detailed Implementation

[0019] This invention includes a laboratory integrated on a chip and its manufacturing process. The laboratory has the following characteristics:

[0020] a) A three-dimensional structure of one or more biocompatible microchannels, susceptible to thermal processes limited by the melting temperature of the substrate material, which allows i) simultaneous processing of different performance requirements on the same sample or different types of samples, ii) incorporating microfluidic processes that utilize physical effects occurring in the three-dimensional structure, such as decanting particles in a fluid suspension without the use of filters, or iii) physically cutting different regions of the chip to isolate them as needed (chemical, thermal, or optical insulation).

[0021] b) One or more biocompatible printed electronic circuits that allow i) local (only in one area of ​​the chip) measurement and internal operation of microfluidic processes, ii) heating only one area of ​​the chip and accurately measuring it without affecting the rest of the processes performed therein, being able to transmit electrical signals in the desired area of ​​the chip to perform electronic readings and operate actuators (heaters, lamps, sensors, etc.) integrated on the chip, iii) using the electronic track design itself to generate active structures such as heaters, electrodes, or antennas, iv) combining electronic components (sensors or actuators) connected to electronic tracks within the chip itself, said electronic components being in contact with or very close to fluid or areas that may require fluid, or v) ensuring that the chip is fully electrically connected to any actuator, sensor, or external controller.

[0022] refer to Figure 1 The lab-on-a-chip according to the invention comprises multiple microchannels (2), with measurement or reaction chambers (3) located within the microchannels (2) for analysis. It also includes printed electronic circuitry (7), which defines several thermal actuators in the form of heaters (12), several sensors in the form of electrodes (13), and includes electronic components (10). Fluid processes, such as mixing, filtering, decanting, or heating of fluids, will be performed within the microchannels.

[0023] exist Figure 3 In the middle layer, a driving layer is visible, in which fluid (4) separated from an external driving system (not shown) is encapsulated by a piston (5); an intermediate layer in which the measurement or reaction chamber (3) is positioned; and a lower metal layer having printed electronic circuitry (7) on which electronic components such as sensors (10) and actuators (11) perform measurement and control processes of the measurement and reaction chamber (3) are located. All microchannels (2) in the different layers are interconnected and connected to the outside of the chip vias (8). The printed electronic circuitry communicates with the outside through defined electronic contacts (6).

[0024] The first step of the manufacturing method of the present invention involves designing all channels, circuits, and actuators by a complete chip processor using various methods, which will require specific analysis. This design is performed on a computer, for example, using a suitable program such as AutoCAD.

[0025] like Figure 4 As shown, the fabrication of the upper layer begins with the use of a base material (1), thereby obtaining a component with reduced dimensions, which is then processed. Some available processes are CNC machining, laser ablation, and injection molding or hot stamping of thermoplastic parts. Through this processing, through-holes (8, Figure 4 B,4C) and microchannels (2, ) connected by the holes. Figure 4 D).

[0026] exist Figure 5 In the middle, you can see the manufacturing Figure 3 A method for the intermediate layer of a microfluidic chip. In this method, a measurement chamber (3) and a cavity (15) are fabricated, wherein electronic components are housed in the cavity (15) during the bonding of multiple layers.

[0027] exist Figure 6 In the middle, you can see the manufacturing Figure 3 The method for the lower layer of the chip. Starting from a biocompatible substrate (1) [A], a metallization process [B] is performed, thereby producing a printed circuit (7). Photoresin (9) is deposited on the metal layer [C] to allow for development processes by photolithography [D] and acid etching [E], thereby fabricating a biocompatible printed electronic circuit. After removing the exposed bonding resin (6) [F], the necessary microchannels and vias (8) are fabricated [G]. In this example, only vias (8) are present.

[0028] Finally, before bonding the layers that make up the microfluidic chip, actuators (10) and sensors (11) or heaters are placed on the areas of the chip for which they are designed [H]. In other embodiments, heaters or antennas may be added.

[0029] More specifically, the biocompatible metal layer can be deposited by methods such as electroplating, sputtering, or adhering a metal foil to a substrate. Functionalization of the metal layer is achieved by photolithography, first by depositing a photosensitive resin layer (6), which is selectively activated by exposing specific areas of the surface to a photosensitive resin sensitizer (ultraviolet, visible, or infrared light, depending on the type of photosensitive resin). Once the resin is exposed, it is developed, and the metal deposited on the sensitized areas of the resin is removed by etching or chemical etching processes, producing a specific metallization pattern as described above. Metallization is then performed from a polymer substrate, such as PMMA, using conductive biocompatible materials such as aluminum, gold, titanium, ITO, or nitinol.

[0030] To perform surface metallization, the polymer surface is first cleaned using a volatile solvent such as ethanol or acetone to remove any residue. This solvent evaporates rapidly without leaving any residue, and the surface is also sterilized. After cleaning, an adhesive resin, such as epoxy resin, is deposited to create a uniform layer several tens of micrometers thick. A metal foil is then deposited onto this newly formed layer, and uniform pressure is applied across the entire surface to ensure the layer's continuity. Several methods are used for this: applying pressure using a hot roller laminator or inserting the component into an automated hot plate press. This method requires specific curing of the resin at a temperature between 65°C and 100°C, and applying pressure between 0.5 and 3 tons for approximately 5 to 15 minutes.

[0031] Acid etching can be performed using various solutions, such as 110 volumes of equal amounts of hydrogen peroxide and 37% fuming hydrochloric acid. This solution can etch the metal without damaging the polymer substrate, leaving the electronic circuitry printed on the polymer surface, the exposed portion of which still has the adhesive resin layer used for metallization. This resin, along with the adhesive resin of the exposed metal layer after this method, is removed using organic solvents such as acetone, isopropanol, or ethanol. These organic solvents etch the resin without damaging the underlying polymer substrate or the printed electronic circuitry.

[0032] Therefore, the remaining components will have a specific metal design that can be used as the basis for electronic components within integrated devices and for bidirectional transmission of electrical signals with connected electronic systems.

[0033] The closed piston (5) isolates the packaging fluid (4) in the lab-on-a-chip from an external pulse mechanism that operates the closed piston (5) via a mobile piston connected to a hole (14) in the piston. The piston can manipulate the fluid in both directions, generating either impulsive or suction forces. The movement of the piston is controlled by an external electronic system automated with the aid of specific software for performing a particular type of analysis.

[0034] The connections between the layers that make up the device ( Figure 7 A-7D) is produced using organic solvents and a combination of pressure and temperature, with or without the aid of additional adhesives. Through this manufacturing process, such as... Figure 7 As shown in Figure D, a complete device with multiple layers was obtained.

[0035] The final device can have several polymer layers, or even different thicknesses between 1 and 10 mm. The microchannels are connected to each other through a designed chamber (3), and different printed electronic layers can be connected to each other by physical contact with each other in certain areas through overlapping layers or paths.

[0036] By combining these structures, a range of functions can be performed, allowing the study of certain parameters using three widely used analytical techniques: amplification and detection of gene sequences via polymerase chain reaction (or PCR), detection and quantification of specific antibodies and antigens using enzyme-linked absorption immunoassay (or ELISA), and detection of biochemical parameters and ions using electrodes or electrochemical detection. Data collected by the sensors will be used to monitor the progress of fluid within the microchannel (2) and can be used to feedback the operation of the actuator, thus enabling precise and safe volumetric pulses, and even the use of Peltier cells, variable temperature resistors (NTCs), or thermistors to change the temperature of the liquid. Furthermore, communication between data collected by these sensors (e.g., integrated thermal sensors (NTCs) or optical actuators (LEDs)) and electronics connected to the actuator platform (not shown) will create a closed circuit in which each action of the mechanical system can be visualized, controlled, and spatially provisionally parameterized, as well as the real-time monitoring of the propulsion of the liquid within the microchannel (2).

[0037] The laboratory is also equipped with independent and activated heating zones, which can be heating tracks on the metallization layer (for applications where heating rate is not a high priority) or rapid heating boxes.

[0038] In order to control those electronic components included in the laboratory and to collect data from the laboratory sensors, a series of contact electrodes have been configured that, through their connection to the central electronics, are able to transmit information collected by the sensors and measure the electrodes of components including microchannels, and enable them to communicate with the processor integrated into the analysis system.

[0039] The entire process can be carried out on an industrial and serialized basis by using inexpensive materials that are easy to manipulate or manufacture, such as PMMA, through metallization steps of photolithography, and by creating microchannels through laser engraving, micromilling or hot embossing.

[0040] By creating a three-dimensional microfluidic chip laboratory structure that is biocompatible and easily affected by thermal processes limited by the melting temperature of the substrate material (e.g., polymethyl methacrylate 105° or COC 160°), the following objectives were achieved:

[0041] a) Simultaneously perform different physical, chemical, or biological processes with different performance requirements on the same sample or different types of samples.

[0042] b) Microfluidic processes that utilize physical effects occurring in three-dimensional structures, such as decanting particles in a suspension of fluid without the need for filters.

[0043] c) Physically cut different areas of the chip to isolate them as needed (chemical, thermal, or optical insulation).

[0044] By leveraging the fact that any area of ​​a lab-on-a-chip can be converted into a biocompatible printed circuit, the following objectives were achieved:

[0045] a) Capable of localized (only within a region of the chip) measurement and internal manipulation of microfluidic processes. It can heat only one area of ​​the chip and measure it precisely without affecting the rest of the processes being performed on it. It can transmit electrical signals in the desired area of ​​the chip, perform electronic readings, and operate actuators (heaters, lamps, sensors, etc.) integrated on the chip.

[0046] b) Use the design of the electronic track itself to create active structures such as heaters, electrodes, or antennas.

[0047] c) The ability to integrate electronic components (sensors or actuators) connected to the electronic track into the chip itself, the electronic track being in contact with or very close to the fluid or area that may require them, thereby minimizing all factors that may interfere with operation or measurement.

[0048] d) Ensure that the chip is fully electrically connected to any external actuators, sensors, or controllers.

Claims

1. A method for layered manufacturing of a lab-on-a-chip, characterized in that: The method includes the following steps: With the help of computer programs, the printed circuits (7), the mixing and reaction chambers (3), the microchannels (2), and the space (15) for placing electronic components are designed in each layer; Different voids and channels are machined in one or more biocompatible substrates, which will form the mixing and reaction chamber (3), the microchannel (2), the hole (8) connecting the microchannel and the space (15) for subsequent placement of electronic components; The surface of the printed circuit (7) to be integrated according to the design made in the first step is metallized with a biocompatible conductive material; The printed circuit (7) is produced by photolithography and acid etching; The electronic components are bonded into the corresponding spaces (15); wherein the electronic components are actuators (11) or sensors (10); Joining together all the layers that make up the final laboratory, Metallization is achieved by adhering a pre-made biocompatible conductive material to the biocompatible substrate using a resin. The biocompatible conductive material is one or more of the following materials: aluminum, silver, gold, platinum, titanium, ITO, graphene, or nickel-titanium. The biocompatible substrate includes one or more of the following materials: polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), poly(3,4-ethylenedioxythiophene) (PEDOT), cyclic olefin copolymer (COC), polycarbonate, or silicon.

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