Conducting composite for analytical microchip

FIELD: microtechnology; manufacture of microchip electrode systems for microanalytical devices.

SUBSTANCE: proposed conducting composite incorporates elastomer, conducting polymer, and conducting carbon filler in the form of polymethyl methacrylate. Proportion of components is as follows, mass percent: conducting carbon filler, 95-97; elastomer, 1-2; polymethyl methacrylate, the rest. It is most reasonable to use glass-reinforced carbon or granular graphite as conducting carbon filler and polydimethyl siloxane, as elastomer. To facilitate its use conducting composite may be transformed to suspension in volatile concentrated solution or hexane or cyclohexane in dichloroethane. Resistivity of dried composite is 0.05 - 0.14 Ohm-cm.

EFFECT: facilitated preparation and use, enhanced chemical and biological inertness of composite.

5 cl, 1 dwg, 1 tbl

 

The invention relates to micro-and can be used in the manufacture of the electrode system of the microchip for microanalytical devices for different purposes. The most effective to use in the design of the biochip to contact assay with a biologically inert material.

Known execution electrically conductive elements of the analytical microchip in the form of the electrode system, comprising contacting the analyzed biological or chemical breakdown metallic pad, the United electrical slats. Gas metallizing coating can be made of noble metal is Pt, Au, Ag (see, for example, RU 2200338, G 03 F 7/00, 7/06, 2003; US 2002179444, G 01 N 27/333, 2002).

However, this construction is expensive because of the use of noble metals and-low-tech, which is unacceptable in the manufacture of disposable microarray diagnostic systems.

These circumstances have led to the necessity to collect chemically and biologically inert, electrically conductive composites. Such is the composite containing granules, each of which contains one or more electrically non-conductive polymers and particles of one or more electrically conductive fillers selected from metals, their oxides, or alloys (US 5106540, N 01 In 1/06, 1992; DE 4315382 B 01 J 2/30, C 08 L 83/04, 09 With 3/12, 04 41/84, 35/00, 41/87, 1993; GB 2054277, N 01 10/12, 1981; EN 2096847, N 01 1/02, N 01 1/22, 1997). To enable load monitoring positive temperature coefficient and increase the conductivity of the composite particles of the electrically conductive filler are dendritic, fibrous or pointed structure, so that they are electrically insulating at rest, but conductive under the influence of mechanical deformation or electrostatic charge. As electrically non-conductive polymer is most appropriate to use elastomer (EN 222065, N 01 7/02, H 01 L 51/30, 2004).

However, the manufacture of these compositions ethnologica, in relation to chemical and biological samples requires the use of precious metals, as in the embodiment of the patent RU 222065 obtain the target product is sensitive to temperature and mechanical stress, which limits its scope.

Also known electrically conductive composite for analytical microchip containing graphite and polymeric binder is an acrylic emulsion or a fluorine-containing elastomer. When the target product is obtained and is applied at the place of use in the form of an aqueous suspension ingredients (US 6710259, N 05 To 1/09, 2004; US 4818438, N 01 In 1/06, 1989), or polytetrafluoroethylene (EN 2061713, C 08 L 27/18, C 08 K 3/00 C 09 D 5/24, 127/18, 08 3:04 3:28, 1996).

However, obtaining and using these options, the composite ethnologica because of the need for long-term (24-hour) drying the intermediate product is a water suspension of a mixture of components if the temperature is high, and possible shrinkage of the target product.

Closest to the claimed is electrically conductive composite containing elastomer, elektronoprovodyaschie polymer based on tetrafluoroethylene (TPV) and carbon conductive filler in the form of soot of different origin (acetylene, furnace, etc. or a mixture of soot with synthetic or crystalline graphite in the following ratio of ingredients, wt.%:

elastomer40÷85
carbon conductive filler10÷66
elektronoprovodyaschie the polymer backbone TPV15÷60

(US 4547311, N 01 In 1/06, 1985).

However, getting a prototype composite ethnologica due to the lengthy processing procedures of raw materials in the preparation of the working mixture in the presence of ligands (MgO) under the control of the viscosity and subsequent drying of the intermediate product is alcohol-ketone suspension of graphite with soot if the temperature is high, and possible shrinkage of the target p is oduct. While it is inconvenient to use because of the need for its retention in solution of lower alcohols or ketones to prevent irreversible drying and changes in physical properties. In addition, this composite is chemically and biologically inert, which leads to denaturation and degradation of the studied analytical sample, as well as the adsorption of low molecular weight components of the water-salt buffer solutions, i.e. distortion of the results of the analysis.

An object of the invention is to improve the manufacturability of the preparation and use of the composite, as well as its chemical and biological inertness.

The solution of the stated technical problem is that in the electrically conductive composite for analytical microchip containing elastomer, elektronoprovodyaschie polymer and conductive carbon filler, as elektronoprovodyaschego polymer is polymethylmethacrylate (PMMA) in the following ratios, wt.%.:

carbon conductive filler95÷97
elastomer1÷2
PMMAthe rest of it.

A causal relationship between the changes and achieved technical results which is that PMMA has a high inertia to chemical and biological samples by simultaneous chemical affinity with the substrate and other structural elements of the analytical microchip, which is important for use in the devices of the considered destination. When this replacement is known elektronoprovodyaschego of the polymer PMMA provides the possibility of dissolution of the semifinished product and the target product in volatile concentrated solution of hexane or cyclohexane dichloroethane, which allows to store the composite in dry form and adjust its consistency when applied at the place of use, and the volatility of the solvent, including the impact on the material of the substrate of the microchip when forming the conductive layer, dramatically accelerate the procedure of drying the composite.

The ratio of ingredients of the composite set of calculation of a suitable combination of its strength and electrical conductivity.

As the conductive carbon filler is most expedient to use the glass carbon or granular graphite, it is better bimodal mixture to seal the conductive structure, which has the consequence of increasing conductivity.

To improve the biocompatibility of the composite analyzed with the breakdown as suitable elastomer used is to use polydimethylsiloxane (PDMS), which is considered the appointment has not previously been used (see, for example, WO 02/010752, G 01 N 33/52, 2002).

We offer conductive composite is obtained by mixing the constituent components with subsequent suspendirovanie in volatile concentrated solution of hexane or cyclohexane dichloroethane, processing in ultrasonic homogenizer and (if necessary) by drying at room temperature. In the case of storage of the dried composite before application to the microarray his pre-treated with the same solvent until the desired consistency.

Used in this technology and the structure of the liquid form of the desired product solvent (volatile concentrated solution of hexane or cyclohexane dichloromethane) is new. He is able to dissolve used as the elastomer, and PMMA.

Technical characteristics of the variants of the composite resistivity ρ (Om·cm) and the physical properties listed in table 1 for the results of the author's trials compared with the prototype.

Variants of the composite containing 95÷97 wt.% carbon filler in the form of soot, fine glass carbon, odnomodovogo (10 μm) and bimodal (10+1 μm) granulated graphite, 1÷2 wt.% elastomer in the form of PDMS or natural rubber, PMMA - rest, have a low specific resistance, good discharge performance is of ρ =0,05÷0,14 Om·cm (prototype ρ=0,06 Om·cm). When this optimal composite (containing 96÷97 wt.% granular graphite, 1,5÷2 wt.% natural rubber and 1÷2.5 wt.% PMMA) are plastic, which allows their use as electrically conductive putty. When reducing the carbon content of the filler (89-95 wt.%) with a simultaneous increase in the content of PMMA (4,7÷to 9.0 wt.%) the resistivity of the composite increases significantly, reaching 50 Ohm·see Sample containing 95 wt.% bimodal graphite, 0.3 wt.% elastomer and 4 wt.% PMMA is permeable, and therefore it cannot be used on this purpose. The increased carbon content of the filler (97÷98 wt.%) due to the minimal content of the elastomer and PMMA (1 wt.%) reduce the strength of the target product (after drying the composite material becomes brittle and breaks down quickly at the place of application).

The drawing shows the design of the analytical microchip electrode system which is made on the basis of the proposed composite.

Analytical microchip contains a substrate 1 of PMMA, which is formed metallized areas 2 and 3 summarize the findings for connecting the microchip to the external electrical circuit. Areas 2 and 3 are electrically connected with the electrode 4 is 5, printed on the surface of the substrate 1 for the formation of the electrode coating of the bottom microanalytical chambers 6 and 7 are located above them. Elements 6 and 7 are formed by using screen printing in microproteinuria photoresistive protective layer 8 of a thickness of 40 microns, pre-printed metallic working surface of the substrate 1. On the outer surfaces of the elements 4, 5 and 8 tightly plotted cover 9 made of a solid dielectric. In this example, the cover 9, as the substrate 1, made of PMMA to provide rigidity and transparency of the design. In the cover 9 coaxial electrodes 4 and 5 are through holes for education microanalytical chambers 6 and 7 by volume of 100 μl. Camera 6 and 7 are connected by 10-mm capillary 10 section 2500 μm2, wepreserve in the cover 9.

In microanalytical camera 6 and 7 contribute analyzed a sample of the electrolyte and produce electrophoresis using an electric field applied to the electrodes 4 and 5. When the content of the ingredients used for the manufacture of electrodes 4 and 5 variants of the composite, in the claimed limits electrophoresis allows you to fractionate a wide class of bioassay on electrophoretic mobility.

As explained above examples, the technical use of the present invention is the I of the improving technology of preparation of the target product (composite obtained by mixing the components of its three simple components), manufacturability of its use (up to application in the form of putty), as well as its chemical and biological inertness (confirmed by chemical and biological inertness components).

Other types of positive effect, derived from the achieved technical result is to reduce the complexity and intensity of the manufacture and use of composite.

1. Conductive composite for analytical microchip containing elastomer, elektronoprovodyaschie polymer and conductive carbon filler, characterized in that as elektronoprovodyaschego polymer it contains polymethylmethacrylate under the following ratios, wt.%:

Carbon conductive filler95÷97
Elastomer1÷2
PolymethylmethacrylateRest

2. Conductive composite according to claim 1, characterized in that it contains carbon conductive filler in the form of a glass carbon.

3. Conductive composite according to claim 1, characterized in that for reducing the electrical resistivity of the target product it contains conductive carbon of napolnitel is in the form of a bimodal mixture of granulated graphite.

4. Conductive composite according to claim 1, characterized in that the elastomer he includes polydimethylsiloxane.

5. Conductive composite according to claim 1, characterized in that it is volatile suspended in a concentrated solution of hexane or cyclohexane dichloromethane.



 

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