Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
  • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
  • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
  • B81C1/00023—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems without movable or flexible elements
  • B81C1/00119—Arrangement of basic structures like cavities or channels, e.g. suitable for microfluidic systems
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
  • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
  • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
  • B01L3/502707—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the manufacture of the container or its components
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2300/00—Additional constructional details
  • B01L2300/06—Auxiliary integrated devices, integrated components
  • B01L2300/0627—Sensor or part of a sensor is integrated
  • B01L2300/0645—Electrodes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2300/00—Additional constructional details
  • B01L2300/08—Geometry, shape and general structure
  • B01L2300/0809—Geometry, shape and general structure rectangular shaped
  • B01L2300/0816—Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2400/00—Moving or stopping fluids
  • B01L2400/04—Moving fluids with specific forces or mechanical means
  • B01L2400/0403—Moving fluids with specific forces or mechanical means specific forces
  • B01L2400/0415—Moving fluids with specific forces or mechanical means specific forces electrical forces, e.g. electrokinetic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2400/00—Moving or stopping fluids
  • B01L2400/04—Moving fluids with specific forces or mechanical means
  • B01L2400/0475—Moving fluids with specific forces or mechanical means specific mechanical means and fluid pressure
  • B01L2400/0487—Moving fluids with specific forces or mechanical means specific mechanical means and fluid pressure fluid pressure, pneumatics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B2201/00—Specific applications of microelectromechanical systems
  • B81B2201/05—Microfluidics
  • B81B2201/058—Microfluidics not provided for in B81B2201/051 - B81B2201/054
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B2203/00—Basic microelectromechanical structures
  • B81B2203/04—Electrodes

Definitions

• the present invention refers to a method to produce a microfluidic device and to a device obtained from such a method, which is used particularly but not exclusively in the fields of bioengineering and energetics .
• microfluidic devices that are used in the field of biotechnology and, in particular, of diagnostics and pharmaceutics, in chemical processes and in energy systems, like for example fuel cells.
• Such devices are made up from microchannels, formed inside a material in the form of grooves, or "open channels” , and subsequently made to stick to a support structure (substrate) that makes it watertight, that contain at least one electrode.
• a support structure substrate
• organic and inorganic fluids that can be electrically stimulated through signals applied to the aforementioned electrode.
• Another typical application can be that related to the detection of electric currents in the fluids in transit through the microchannels, as well as the presence of ions or of electrically charged molecules.
• microfluidic devices capable of housing connections of the electrical type ⁇ electrical microfluidic devices" or EMD
• EMD electrical type ⁇ electrical microfluidic devices
• the structure of the microchannels with micrometric dimensions is commonly obtained through moulding in a polymer material, like for example polydimethylsiloxane (PDMS) . Such a structure is then subsequently made to stick on a substrate in which there is a network of electrodes .
• a polymer material like for example polydimethylsiloxane (PDMS)
• Electrodes are made through per se known metal deposition methods, like for example sputtering, or through methods based on lithography, such as lift-off and etching.
• an electric field that is not evenly arranged inside the microchannels is generated.
• Such an electric field indeed tends to be mostly located in the region of space delimited by the two opposing electrodes which, in the case in which the electrodes are positioned as above, only takes up a small area inside the microchannels .
• the arrangement of a non even electric field inside the microchannels ensures that the portion of fluid that is closest to the electrodes is electrically stimulated in a substantially different manner with respect to the corresponding portion of fluid farthest from the electrodes.
• the manufacturing of the microfluidic devices passes through a first step in which the microchannels are formed and a second phase in which the electrodes are formed.
• the purpose of the present invention is therefore that of providing a method to produce a microfluidic device that is capable of overcoming the aforementioned drawbacks of the prior art in an extremely simple, cost-effective and particularly functional manner.
• one purpose of the present invention is that of providing a method to produce a microfluidic device that is capable of obtaining vertical electrodes that face into the microchannels.
• Another purpose of the present invention is that of providing a method to produce a microfluidic device that has a small number of manufacturing steps .
• a further purpose of the present invention is that of providing a microfluidic device made from plastic material that is flexible and suitable for simultaneously receiving electric and mechanical stimulations .
• figure 1 is a flow chart that illustrates the steps of the method to produce a microfluidic device according to the present invention
• FIGS. 1a, 2b, 2c and 2d are four schematic views of the structures that respectively come from four of the steps of the method of figure 1;
• figure 3 is a schematic perspective view of a first embodiment of a microfluidic device obtained with the method of figure 1;
• figure 4 is a schematic perspective view of the microfluidic device of figure 3 and of the corresponding method for injecting electrically conductive material, as one of the possible methods that can be used;
• figure 5 is a schematic perspective view of a second embodiment of a microfluidic device obtained with the method of figure 1.
• a method to produce a microfluidic device 50, 60, 70 is shown, such a method and the relative steps being wholly indicated with reference numeral 100.
• the method 100 comprises a step 10 of forming the microchannels in a watertight structure.
• a step 10 not only obtains a first fluidic microchannel network 51, 62, 72 i.e. the microchannels that can be filled with one or more fluids, organic and inorganic, to be stimulated or controlled, but also advantageously obtains a suitable second network of microchannels 52, 61, 73 that can be filled with an electrically conductive material that can act as impedance or conductor and interacts with such a fluid to be stimulated or controlled.
• such electrically conductive material can be intended to create electrodes which, through the application of a potential difference, generate an electric field inside the first fluidic microchannel network 51, 62 72 for the stimulation or the control of the fluids contained in it.
• Such electrically conductive material can also be intended to create electrodes that are suitable for detecting an electric field inside the first fluidic microchannel network 51, 62, 72.
• Such a step 10 to produce both the fluidic microchannels 51, 62, 72, and those suitable for forming the electrodes 52, 61, 73 comprises an initial step 20 of manufacturing a die 30, 31 for creating the microchannels 51, 62, 72 and 52, 61, 73 themselves.
• This initial manufacturing step 20 in turn comprises a step 21 consisting of the deposition of a layer 31 of photoresistive material on a sample comprising a substrate 30, like for example a substrate of silicon or of polymer material. On such a layer 31 of photoresistive material an impression is obtained corresponding to the positions of the microchannels 51, 62, 72 and 52, 61, 73 through for example the controlled exposure of the die 30, 31 to a light beam.
• a photoresistive mask which is generated thanks to the subsequent step 23 of exposure of the photoresistive mask itself to UV rays, is thus formed.
• the layer 31 of photoresistive material is removed from the upper surface of the substrate 30, thanks to the action of the UV rays, only at the areas identified by the aforementioned impression.
• a die 30, 31 is obtained to produce the microchannels 51, 62, 72 and 52, 61, 73.
• the method 100 to produce the microchannels 51, 62, 72 and 52, 61, 73 comprises a step 11 of casting a plastic material 32, like for example PDMS, as visible in figure 2b, on such a die 30, 31 forming a provisional structure 30, 31, 32. From such a provisional structure 30, 31, 32, in a subsequent step 14, the die 30, 31, is removed thus forming a portion of a microfluidic device, illustrated in figure 2c, formed by the single layer of plastic material 32 in which the fluidic microchannels 51, 62, 72 and the microchannels to produce the electrodes 52, 61, 73, have been formed.
• Such a ⁇ layer of plastic material 32 is joined (step 15) to a closure substrate 33 in a manner such as to close the already previously formed microchannels 51, 62, 72 and 52, 61, 73, in a watertight structure.
• the network of microchannels 52, 61, 73 dedicated to the creation of the electrodes is then advantageously filled, in a specific step 16, with an electrically conductive material in the fluid state, like for example a conductive polymer, an ionic solution or molten metal, so as to act as impedance or conductor.
• Such electrically conductive material is injected, in the same manner as the work fluid, through injection means 74, like for example syringes, in cavities 71 formed at the ends of the microchannels 51, 62, 72 and/or 52, 61, 73.
• Such electrically conductive material can thus operate both in the fluid state, and can be a material (like for example the same polymer, suitably doped, used in order to obtain the microchannels, or low-melting alloys) configured so as to solidify after the aforementioned injection step.
• the electrically conductive material injected into the network of microchannels 52, 61, 73 can be a non conductive polymer doped with conductive material, like for example carbon nanotubes, or micrometric metal spheres or a combination thereof .
• a microfluidic device 50 is created in which the microchannels 52, 73 filled with electrically conductive material intersect the microchannels 51, 72 containing the work fluid.
• the electrically conductive material polymerises, thus passing from the fluid state to the solid state, and therefore forms some electrodes that come into contact with the work fluid without mixing with it.
• a network of microchannels 61 is created, to produce electrodes, that is on a different plane with respect to that on which there is the microfluidic microchannel 62.
• the two types or networks of microchannels 61, 62 develop separately, but preferably at the same time, on two portions of substrate that are then joined to form the microfluidic device 60.
• the stimulation or the control action carried out by the electrically conductive material on the work fluid is obtained through capacitive effect.
• the microfluidic device obtained through the application of such a manufacturing method, is completely flexible, in a manner such as to allow, for example at the same moment in time, a stimulation of mechanical and electrical type .
• the electrodes formed due to injecting electrically conductive material in the fluid state inside the microchannels suitably obtained do not indeed jeopardise the flexibility of the device .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Analytical Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Dispersion Chemistry (AREA)
• Microelectronics & Electronic Packaging (AREA)
• General Health & Medical Sciences (AREA)
• Hematology (AREA)
• Clinical Laboratory Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Micromachines (AREA)
• Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

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• 2010
  • 2010-03-31 IT ITMI2010A000550A patent/IT1399361B1/it active
• 2011
  • 2011-03-29 WO PCT/IB2011/000677 patent/WO2011121427A2/en active Application Filing

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