JP6213987B2 - Micro glucose sensor - Google Patents

Description

  The present invention relates to a microneedle microglucose sensor that combines 3D MEMS-based exposure technology, nanoimprint technology, and other microfabrication processes.

  Diabetes is one of the major public health problems facing modern people. It is well known that diabetic complications can be controlled when glucose levels are strictly limited within the normal physiological range of 110 mg / dL ± 25 mg / dL (Non-Patent Document 1). Measuring blood glucose levels for diabetics was published in 1971 (Non-Patent Document 2). In addition, because glucose is one of the main intermediates in food, beverages and biofluids, low-cost local measurements of sugar levels are particularly important in the food industry, physiological processing, and biofuel cells. This is particularly necessary for high quality production and high efficiency (Non-Patent Document 2). As a result, great efforts have been made to develop a highly reliable and high-performance glucose measuring device (Non-patent Document 3).

  Various glucose measurement methods have been developed, some of which are commercially available. These glucose measurement techniques are classified into optical, transdermal, electrochemical, piezoelectric, thermoelectric, and acoustic based on the measurement principle (Non-Patent Documents 2, 3, and Patent Document 1). The demand for automated, fast and accurate medical, biotechnological applications, such as for example diabetes applications, has a fast response (1-5 min.) For glucose measurement, It has good accuracy (maximum deviation is 10 mg / dL or less), high sensitivity (2 mg / dL), large range (20 to 600 mg / dL), and high stability (± 5% during operation) (Non-Patent Document 2). As a result, the mainstream of glucose measurement is still an electrochemical biosensor due to its simple principle and ongoing development. Electrochemical biosensors are based on the principle of amperometry based on the oxidation or reduction of electrochemically active substances or the principle of potentiometry based on local pH fluctuations due to local generation of gluconic acid Is done. A glucose sensor for potentiometric measurement has a limit in sensitivity, but it can be effective when the amplitude of the concentration change of the sample is on the order of several orders. A potentiometric glucose sensor can obtain a signal that is linearly dependent on the concentration of the analyte, which is the main criterion for the development of electrochemical glucose biosensors. Amperometric glucose sensors are usually classified into three different categories based on the mechanism of electrochemical (charge transfer) reactions. The mechanism of charge transfer is identified from the enzyme, consisting of (1) the oxidation of glucose by the enzyme in the natural state, (2) the mediated charge transfer using low molecular weight compounds, and (3) the normal conducting organic salt. Direct charge transfer to the other electrode. In recent years, with the development of nanomaterials, non-enzymatic glucose sensors have developed rapidly in the last 15 years. The mechanism of direct glucose oxidation at metal and carbon electrodes, while still uncertain, provides high sensitivity, long-term stability, resistance to thermal effects, low cost, and a simple and reproducible manufacturing method.

US Pat. No. 5,605,152 US Pat. No. 5,165,407 US Pat. No. 5,586,553 U.S. Pat. No. 7,976,492 Japanese Patent Application No. 2009-16896 Japanese Patent Application No. 2006-045231

E. Wilkins, P. Atanasov, Glucose monitoring: state of the art and future possibilities, Med. Eng. Phys. Vol. 18, No. 4, pp. 273-288, 1996 N. S. Oliver, C. Toumazou, A. E. G. Cass and D. G. Johnston, Glucose sensors: a review of current and emerging technology, Diabetic Medicine, 26, 197-210, 2009 Joseph Wang, Electrochemical glucose biosensors, Chem. Rev. 2008, 108, 814-825 E. S. Wilkins, Towards implantable glucose sensors: a review, J. Biomed. Eng., Vol. 11, 354-361, 1989 WH Lee, JH. Lee, WH. Choi, AA Hosni, I. Papautsuky, PLBishop, Needle-type environmental microsensors: design, construction and uses of microelectrodes and multi-analyte MEMS sensor arrays, Meas. Sci. Technol. 22 2011 042001 K. Seidl, S. Spieth, S. Herwik, J. Steigert, R. Zengerle, O. Paul, P. Ruther, In-plane silicon probes for simultaneous neural recording and drug delivery, J. Micromech. Microeng. 20 (2010 ) 105006 Y. Wang, F. Caruso, Enzyme encapsulation in nanoporous silica spheres, Chemistry Communication, 2004, 1528-1529 S. Wu, H. Ju, Y. Liu, Conductive mesocellular silica-cabon nanocomposite foams for immobilization, direct electrochemistry, and biosensing of proteins, Adv. Funct. Mater. 2007, 585-592 S. Bao, C. M. Li, J. Zang, X. Cui, Y. Qiao, J. Guo, New nanostructured TiO2 for direct electrochemistry and glucose sensor applications, Adv. Funct. Mater. 2008, 591-599

There are various electrochemical glucose sensors using different shapes and sizes, or different electrode materials, but the small needle glucose sensor is used for applications such as measuring subcutaneous glucose concentration due to its low infiltration and high sensitivity. It is suitable (patent documents 2-4, non-patent documents 1-4). In addition, since it is usually manufactured using a microfabrication technique, it is possible to integrate other electronic components in order to realize more functions. For example, a small needle electrochemical sensor can be used to measure several types of analytes simultaneously. In recent years, hollow needle type structures have attracted attention as glucose sensors because (1) high accuracy can be achieved and (2) fluid transportation is possible. However, in fact, many microfabrication technologies consist of planar processes, but small needle glucose sensors are associated with complex processes. In addition, it is difficult to manufacture a hollow needle structure, and it is more difficult to integrate microelectrodes (Non-Patent Documents 5 and 6). As a result, the above-described technology is not economically competitive. In other words, a new microfabrication technique for manufacturing a hollow small needle type electrochemical sensor should be developed. There is also a need for microfabrication methods related to fluid transport and signal transmission, including optical and electrical, in other microinvestigation applications. Thus, much effort has been expended to integrate microelectrodes and other microstructures onto hollow (capillary) and non-hollow fiber substrates. In fact, fiber microfabrication technology meets the following requirements:
(1) High efficiency electrode on limited surface of small fibers,
(2) Easy integration of different functional materials such as multilayer structure alignment,
(3) Easy mass production.

  In the present application, a 3D MEMS-based exposure technique for producing a micropattern and a structure on a fiber, which economically solves many of the above-described attempts, is disclosed (Patent Document 5). A great deal of effort is required to integrate a large number of functional materials with high sensitivity. It is already known that nano and porous materials significantly increase the electrode surface area. The mesoporous electrode can capture and wrap the enzyme (Non-patent Documents 7-9). As a result, they are used in modern glucose sensors to achieve direct electron transfer without the need for a transmitter. There are similar requirements in other electrochemical reaction systems. In recent years, the applicant has invented a nanoimprint electrode for application to a micro fuel cell (Patent Document 6). Nanoimprint technology is also being developed for other applications. However, to date, no application of nanoimprint technology to glucose sensors and other electrochemical electrodes fabricated on microneedle-type substrates has been reported.

  The present application provides a micro-needle glucose sensor and a new micro-fabrication method of a micro-needle glucose sensor that combines 3D MEMS-based exposure technology, nano-imprint technology, and other micro-machining processes.

Fig.1 (a) is the schematic of the electrochemical glucose sensor concerning this invention, FIG.1 (b) is an enlarged view of Fig.1 (a). It is the schematic of the 3D microfabrication module concerning this invention, FIG. 2 (a) is a figure which shows the 3D microfabrication module of high-resolution photolithography, and FIG.2 (b) 3D nanoimprint module. It is the schematic which shows the manufacture process of the module with respect to photolithography concerning this invention. It is the schematic which shows the manufacture process of the module with respect to 3D nanoimprint mold concerning this invention. It is the schematic which shows the manufacture process of the electrochemical electrode on a fiber concerning this invention.

  Fibers and similar materials have many well-known advantages over conventional wafers. In particular, hollow fibers, or capillaries, are necessary in medical and healthcare applications because the hollow structure can be used as a fluid channel to carry drugs and chemicals. Of course, the hollow structure can replace other functional structures for signal transmission other than the transport of chemicals. The fiber material can have various dimensions and shapes. The diameter ranges from several μm to several mm. The shape is a circle, a rectangle, a polygon, or the like. The microsensor is made on a fiber. The multiple fibers can be machined into the desired product in the form of a single fiber or assembled with other electronic components.

  FIG. 1 is a schematic diagram of a representative electrochemical glucose sensor of the present invention. The glucose sensor is made on a hollow fiber, ie capillary 1. In FIG. 1, the glucose sensor has a three-electrode structure. Of course, a two-electrode structure also works. A minute pattern is formed in the region of the electrodes 2a to 2c. The electrode has a ring shape, a square shape, a circular shape, or the like. The size of the electrode is several to 100 square μm. One or all electrodes are modified by the nanoimprint patterns 3a-3c. The size of the fine pattern is several nanometers to several tens of micrometers. These shapes are columnar, dots, holes, and complex shapes. Of course, the fine pattern is not only formed directly on the substrate, but also made on a layer of UV-reactive material and mixed with other functional materials (such as enzymes, conductive polymers, etc.) Also good. Such nanoimprint patterns are not only provided in large areas for electrochemical reactions, but also provide support for enzymes and nanomaterials. These nanoimprint patterns are useful for biological modification at the electrode and are expected to be highly sensitive.

  FIG. 2 is a schematic view of the 3D microfabricated module of the present invention. In order to mass-produce electrochemical glucose sensors on a fiber substrate with nanoimprint patterns, a new type of 3D microfabricated module as shown in FIG. 2 is required. Two types of 3D microfabricated modules are needed for each of photolithography and nanoimprint. FIG. 2A shows a 3D microfabrication module for high resolution photolithography. FIG. 2B shows a 3D nanoimprint module. The 3D nanoimprint module can also be used for UV nanoimprint or thermal nanoimprint. The 3D photolithography module is made of a UV transmissive material having excellent mechanical properties, such as quartz. The UV nanoimprint module may be transmissive or non-transmissive. Non-permeable modules are possible when no alignment operation is required. If alignment is required, the 3D nanoimprint module must be at least locally transmissive to adapt the alignment mark. Using these 3D microfabricated modules, high resolution patterns including nanoimprint structures are produced on the fiber with high productivity in a continuous stepping-forward mode.

  There are three types of nanoimprint modes for producing microstructures on the fiber: (1) sliding nanoimprint, (2) continuous nanoimprint, and (3) continuous forward nanoimprint. The type of the sliding nanoimprint mode can be prepared by a conventional method. However, the sliding nanoimprint mode is associated with mold and fiber movement, and it is difficult to realize a continuous mode with a minimum of operation, so it is relatively unproductive. Continuous nanoimprint mode requires a roller-type mold that is difficult to prepare. Continuous forward nanoimprint requires a 3D microfabricated module as shown in FIG. Thermal imprint technology is used for these microfabrications with a large aspect ratio and thus a large reaction area. UV nanoimprint technology is recommended due to high productivity efficiency when the pattern is formed on a fiber substrate with a UV sensitive polymer coating. The present invention mainly relates to (3) continuous forward nanoimprint.

  A 3D exposure module that can be used for curved surfaces can be prepared using projection lithography, soft lithography, and other lithography techniques. The module substrate can be prepared using either a flat substrate or a half-pipe substrate. A planar substrate is associated with direct microfabrication of a trench structure on the planar substrate. In fact, the projection lithography technique can only be used for trenches with a depth of 100 μm or less. In addition, projection lithography has a limited resolution, thus limiting the mask pattern, which is not compatible with the nanoimprint process. In order to achieve high resolution patterns in 3D microfabricated modules, multi-photonic polymerization based direct laser writing technology is used. As a result, a 100 nm diameter structure is formed in the half pipe structure. The manufacturing method of the 3D microfabricated module is as follows.

  The module substrate is prepared by combining micromachining and high-precision machining technology. The module substrate may be glass, quartz, metal, other materials including transmissive and non-permeable. Not only a flat substrate but also a half-pipe substrate can be used. FIG. 3 shows a module fabrication process for photolithography on a half-pipe substrate using a lift-off process. The required cleaning is performed (FIG. 3 (a)). A thin resist material 5 is placed on the half-pipe substrate (FIG. 3B). A multi-photonic polymerization based direct laser writing technique is used to form a fine pattern inside the half-pipe substrate. A metal thin film having a thickness of 10 to 1000 nm is deposited. The remaining resist pattern is removed, and a mask metal pattern 6 is formed (FIG. 3C). A fine pattern of the exposure module may be formed using a direct etching process. . FIG. 4 shows a manufacturing process of a 3D nanoimprint mold in a continuous advance mode. A metal layer 7 is deposited in the half-pipe substrate 8 (FIG. 4A). A thick resist mold 9 is then formed using a multi-photonic polymerization based direct laser writing technique (FIG. 4 (b)). Next, a nickel alloy film or other material 10 having excellent mechanical properties is electroplated (FIG. 4 (c)). Next, the resist mold and the seed layer are removed (FIG. 4D). A non-permeable half-pipe substrate can be used. In practice, quartz and other permeable half-pipe substrates are preferred because alignment is possible and more complex microstructures can be realized. It is more preferable when the fiber base is a polymer base.

[Example: Nanoimprinted electrochemical electrode on fiber]
FIG. 5 shows the process of making an electrochemical electrode on a fiber using a combination of nanoimprint and photolithography techniques. The fiber 11 is sandwiched between the nanoimprint modules of the present invention shown in FIGS. 2B and 4 to form a micropattern 12 (FIG. 5B). The nanoimprinted fiber is covered with a Pt metal thin film. Next, it is covered with resists 13a to 13c, introduced into the 3D exposure module of the present invention shown in FIGS. 2 (a) and 3 (however, the fine pattern is different from that of FIG. 2 (a)), and photo A lithography process is performed (FIG. 5C). After development, the Pt film is patterned to form basic electrodes 14a-14c (FIG. 5 (d)). In order to form a reference electrode, a thin resist film 15 is formed and patterned. An Ag thin film having a thickness of 300 nm is formed, and its surface is modified to an AgCl layer 16 having a thickness of about 200 nm (FIG. 5E), and the resist is removed (FIG. 5F). Next, an enzyme and another functional material are introduced into the work electrode 16 (AgCl layer 16) by an ink jet method. Due to the presence of the nanoimprint pattern, enzymes and other functional materials are well confined within the work electrode 16. Spray coating techniques are used to form thin or thick films. Dip coating techniques are also possible. When the passivation layer is formed, the enzyme can be formed on the nanoimprint electrode by a dipping method.

  Details of this embodiment will be described below.

  The 3D exposure module of the present invention is manufactured as follows. A 3D exposure module is formed using a half-pipe substrate. The half pipe substrate is formed by high precision machining. A Cr thin film having a thickness of 120 nm is formed by sputtering the half pipe substrate. Next, a thin resist film is formed in the half pipe substrate. A fine pattern is then formed directly on the half-pipe substrate using a multi-photonic polymerization based direct laser writing technique. After development, etching is performed in an etchant of a Cr thin film.

  Using the 3D exposure module of the present invention, an electrochemical electrode on a fiber is produced as follows. A 330 μm diameter polyimide capillary was used as the substrate. A 3D nanoimprint module was formed on a quartz substrate using the process of FIG. A 50 nm thick Cr / Cu thin film was sputtered onto a half-pipe substrate and then covered with a thick resist solution. Pillar arrays with a diameter of 500 nm and a height of 200 nm were formed using a multi-photonic polymerization based direct laser writing technique. A 150 nm thick Ni film was then electroplated. Next, the resist module and the Cr / Cu seed layer were removed. Using a nanoimprint module, a 500 nm diameter pillar structure is formed directly on a polyimide capillary. The pillar structure has a height of about 100 nm and a pitch of 1 μm. The nanoimprinted polyimide capillary is then covered with a Pt metal thin film. A 3 μm thick Shipley 1830 photoresist is formed on the substrate using spray coating. The fiber covered with the resist is introduced into the 3D exposure module, and an alignment operation is performed. A thin Pt film is patterned to form an electrode structure. In the case of a three-electrode structure, after removing the resist layer, the capillary is again covered with a thin resist film and patterned to form an AgCl / Ag reference electrode. The AgCl / Ag reference electrode is formed as follows. A 300 nm thick Ag film is formed and patterned by a lift-off method. Next, it is immersed in HCl solution, and the Ag film is converted to AgCl. Since the nanoimprint pattern can confine the enzyme in the work electrode, the produced glucose sensor has good reproducibility.

DESCRIPTION OF SYMBOLS 1 Capillary 2a, 2b, 2c Electrode 3a, 3b, 3c Nanoimprint pattern 4, 8 Half pipe substrate 5, 13a, 13b, 13c Resist material 6 Metal film 7 Metal layer 9 Resist mold 10 Nickel alloy film or other material 11 Fiber 12 Micropattern 14a, 14b, 14c Basic electrode 15 Resist film 16 AgCl layer

Claims (8)

A 3D microfabrication module for producing a glucose sensor on a microcapillary,
Half pipe substrate,
And a metal thin film on the half-pipe substrate,
The metal thin film, 3D microfabrication module, wherein a fine pattern for forming a fine structure on the micro capillary is formed by nanoimprint process.   The 3D microfabricated module according to claim 1, wherein the fine pattern is formed so as to form a pillar structure on the microcapillary. The half pipe substrate is a UV transmissive, 3D microfabrication module of claim 1, wherein the nano-imprint process is characterized in that it is a UV-based. The 3D microfabricated module according to claim 1, wherein the nanoimprint process is heat-based. A glucose sensor produced using the 3D microfabricated module according to claim 1,
A microcapillary,
And an electrode on the small capillaries,
The glucose sensor, wherein the electrode has a micropattern and an enzyme is contained in the electrode. A method for producing a 3D nanoimprint module for producing a glucose sensor on a microcapillary,
Depositing a metal seed layer in the half-pipe substrate;
Installing a resist material in the half pipe substrate;
Forming a fine pattern in the half-pipe substrate using a multi-photonic polymerization based direct laser writing technique to form a fine structure on the microcapillary by a nanoimprint process ;
Depositing a nickel alloy film in the half-pipe substrate;
Removing the resist material and the seed layer. A method for producing a glucose sensor on a microcapillary,
And that charged by 3D nanoimprint module manufactured by the method according to claim 6 covering the micro capillary, imprinting the fine pore pattern on the fine capillaries,
Depositing a Pt metal thin film on the imprinted microcapillary;
Covering the Pt metal thin film with a resist;
Covering the previous Symbol micro-capillary, and performing a photolithography process,
Patterning the Pt metal thin film;
Covering the microcapillary patterned with the Pt metal thin film with a thin resist layer, and patterning;
Forming an Ag thin film on the patterned microcapillary;
Immersing the microcapillary on which the Ag thin film is formed in an HCl solution, converting the Ag thin film into AgCl, and forming an electrode;
Introducing an enzyme into the electrode. The method according to claim 7 , wherein the fine pattern has a pillar structure.

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