Karin Potje-Kamloth

Carbon Fiber Microelectrodes

Electrodes of the smallest characteristic dimensions less than few micrometers have unique properties which make them very attractive for use in many electrochemical and biomedical applications. Because of the response of these small electrodes it is possible to change their properties drastically just by variation of the electrode diameter. Depending on their size it is possible to decrease their sensitivity to the effects of solution resistance as well as also to increase their temporal electrochemical resolution.

Electrochemical encapsulation for sensors

Abstract A high-resolution encapsulation procedure suitable for chemical sensors has been developed. It is based on the electrochemical generation of a poly-(oxyphenylene) film at the electrically active areas of the device. The 1.5 to 5 μ thick encapsulation film is selectively deposited on gold, platinum or carbon surfaces. No deposition takes place on aluminium, which allows this metal to be used as a mask. The resistivity of a 2 μm thick film after a four-week exposure to 0.1 M NaCl is 7 × 10 11 Ω cm.

Study of Electric Field Modulation in Organic Field-Effect Transistors

A solid-state test platform has been designed and fabricated that allows characterization of candidate organic semiconductor materials used in organic field-effect transistors. Origins of electric-field modulation in these devices have been investigated. Using a modified four-point-probe technique, it has been found that in addition to the resistance of the organic semiconductor, the resistances of the source and drain contacts are also modulated by the gate electric field. A systematic experimental protocol has been outlined that allows the separation and study of contribution of modulated contact resistances and of the organic film resistance to the overall response. From these measurements the true carrier mobility of the organic semiconductor can be determined.

Electrochemical Encapsulation of Solid State Devices

The need for encapsulation of solid state devices, particularly of those which are chronically exposed to chemical environment, has been long recognized as one of the outstanding problems in their use. These devices range from solar cells to chemical and physical sensors and the nature of the chemical environment varies from atmospheric exposure to biological fluids. Additional corrosion problems can occur due to presence of high electrical fields at the device surfaces and in dielectrics which may be as high as 100 kV/cm. The primary purpose of the encapsulation is to prevent the degradation of the materials from which the device is constructed which might result in the premature device failure. Equally important is the aspect of the electrical safety of the devices which are used for medical purposes or in the chemical environment in which the live electrical components could present operational problems such as contamination of the environment with the electrolytic products, explosion hazards etc..