AN ION SELECTIVE MICROGRIPPER SENSOR DEVICE

Abstract

This thesis presents the design, fabrication, characterisation and testing of a chemically modified electrothermally actuated microgripper. The chemical modification involves the integration of a potentiometric ion selective electrode (ISE) onto a bare electrode fabricated within the tip of the microgripper. This microgripper sensor device is intended for use in the application of detecting, in real time, the movement of key ions that are involved in intercellular communication from a mechanically stressed cell.
An optimised fabrication route for the specifically designed microgrippers, which have tip dimensions of 10 – 60 µm, is described in detail. The fabrication route delivers a high yield (95%) of operational unmodified devices. An 1800 ± 20 µm2 bare gold electrode that is fabricated at the tip of the microgripper is modified into an all solid state ISE that uses PEDOT as the ion-to-electron solid contact. Suitable ionophores that selectively detect K+, Na+ and Ca2+ are used to fabricate potassium, sodium and calcium ion selective microgripper sensor devices.
The quality control and testing characteristics that follow the guidelines defined by IUPAC are performed to ascertain the sensitivity, selectivity and stability of the microgripper sensor devices. Good selectivity is achieved, with limits of detection of 2.4 x 10-4 M, 1.8 x 10-4 M and 2.0 x 10-5 M for the K+, Na+ and Ca2+ devices respectively. Proof of concept experiments of the real life testing of the K+ ISE device used to mechanically stress mouse oocytes gave preliminary measurements that indicate that stress signalling occurs via a switch on mechanism, and that there is a small increase in K+ concentration as applied stress increases. Due to the high systematic error within the calibration process the magnitude of this concentration increase is unknown. The Na+ and Ca2+ ISE devices suffer from interference and sensitivity restrictions respectively so a signal response vs. applied cell stress relationship of these ions is currently unobtainable.