Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Patent
1997-01-27
2000-02-01
Duda, Kathleen
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
430311, G03F 726
Patent
active
06020110&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the fabrication of electrodes for use in an electrochemical test method for a species being detected.
BACKGROUND OF THE INVENTION
There is considerable demand for the testing of species using electrochemical methods. These species include but are not limited to metals, glucose, biochemical species, gases and other redox species. Analysis of these species may be achieved at conventional large electrodes or at microelectrodes. The latter offer improved precision, sensitivity, improved signal to noise ratios, reduced interference from interfering species such as oxygen, and in addition the potential to measure species in highly resistive media. Therefore a considerable effort has been expended on methods to produce these electrodes in a well-defined microelectrode array format that retains all the advantages of single microelectrodes and provides higher currents compared to those obtainable at individual microelectrodes (pA-nA).
Existing methods of fabrication for these electrodes are either by hand using epoxy resin encapsulation (W. L. Caudill et al, Anal. Chem. (1982) 54:2532) which is too time consuming and inefficient, or require expensive equipment, as in the case of fabrication by photo-ablation with lasers (WO-A-9108474) and electron beam etching techniques (M. S. Wrighton, Science (1986) 231:32). Other methods such as fabrication by the adhesion of microporous membranes (J. Wang and J. M. Zadeii, J. Electroanal. Chem. (1988) 249:339) failed due to heterogeneity in the arrangement of the pores resulting in poor reproducibility. J.Osteryoung and T. Hempel, J. Electrochem. Soc. (1986) 133:757, have investigated the use of thin film techniques but these have failed due to adhesion problems between the layers.
An object behind the present invention is to produce a satisfactory microelectrode array at low cost.
SUMMARY OF THE INVENTION
According to the invention, a method for making a microelectrode comprising a layer of apertures through an electrically-insulating layer to reveal an electrically-conducting layer, is characterised by the fact that the apertures are made by photoimaging (the use of substances that can be polymerized by the application of light or the use of substances that can have their bonds broken by the application of light). These light-sensitive materials are also known as photoimageable resists. Their use provides a convenient, economic process for the fabrication of products having properties comparable to those made by more expensive methods. An electrode produced by the method of the invention is suitable for use in analytical methods for the detection of species by an electrochemical reaction, and for incorporation in a suitable instrument.
DESCRIPTION OF THE INVENTION
In one embodiment of the invention, the microelectrode consists essentially of a conducting electrode material deposited on a non-conducting substrate. The substrate may be a polymer layer such as polyester, polycarbonate or polyvinyl chloride.
The conducting material of the electrode layer is not critical. It may be a carbon, gold or another metal in a printable ink formulation or another formulation that is suitable for the chosen deposition process. The electrode material may be deposited on the substrate by a conventional process including, but not limited to, thick film printing (also known as silk screen printing), lithography, vapour deposition, spray-coating, roller-coating or vacuum deposition.
A photoimageable dielectric layer, such as a photoimageable negative resist is then deposited over the conducting electrode material by a second process. This again may be conventional, such as vapour deposition, silk screen printing, spin coating, or lithographic printing.
An image of the required array is then held at the surface of the electrode, and the system is exposed to suitable light source for an appropriate period. The photoimageable layer is then photopolymerised by the light source in those areas that are exposed. In areas that are covered by th
REFERENCES:
Aoki et al. "Diffusion Controlled Current at a Stationary Finite Disk Electrode." J. Electroanal. Chem., vol. 125, 315-320, 1981.
J. Electroanal. Chem., vol. 125, 315-320 (1981).
Analytical Chemistry, vol. 62, 2206-2210 (1990).
Analytical Chemistry, vol. 63, 931-936 (1991).
Arnold Peter Thomas
Williams Stephen Charles
Yon-Hin Bernadette
Cambridge Sensors Ltd.
Duda Kathleen
Rauchfuss, Jr. George W.
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