Papers by Author: Dermot Diamond

Abstract: In recent years, there has been significant progress in a number of sensing technologies related to on-body measurements, such as platforms for monitoring respiration, heart rate, location and movement. In these cases, the sensing element (s) are based on highly effective transducers that are increasingly integrated into garments such that they are becoming innocuous to the user. In contrast, the area of on-body chemical sensing remains highly under-developed. In this paper, we will address the significant challenges that are inhibiting the practical realisation of reliable chemical sensors and biosensors capable of generating accurate data in real time.

Abstract: Solid-contact Ion Selective Electrodes (SC-ISEs) for the detection of lead are prepared on screen printed substrates in order to have low-cost and disposable sensors which may be useful in long-term environmental monitoring. It is shown that the materials used as solid contact layer, the deposition techniques and their thickness affect greatly the performances of the sensors. Poly(3-octylthiophene-2,5-diyl) (POT) and poly-3,4-ethylenedioxithiophene (PEDOT) are employed in this investigation. A trend showing an optimum is found for sensors prepared with POT as the batch reproducibility depends on the amount drop-cast, i.e., thickness. In case of PEDOT which is grown amperometrically the trend is more complex but an optimum for the batch reproducibility is again found depending on the current density. In the latter case, the film thickness and the overoxidation degree of the polymer probably concur in determining a more complex relationship.

Abstract: Spiropyran photochromic compounds can be switched using light exposure between a non-polar spiro form (SP) and a zwitterionic merocyanine form (MC) that is subject to protonation (MC-H+). It has recently been demonstrated by Walsh et al. that, under acidic conditions, electroosmotic flow (EOF) generated in vinyl based spiropyran monoliths can be modulated using light irradiation [1]. In this paper, we report a spiropyran-modified acrylate based monolith which is particularly sensitive to protonation in the MC form, producing a positively charged surface that converts to the unpolar SP form by exposure to white light. When the MC-H+ form is dominant, it produces a charged surface which enables a relatively high flow rate (up to 1.6 μl/min) to be generated under electroosmotic conditions. Upon exposure to white light, the concentration of MC-H+ decreases due to the photo-conversion to the uncharged SP form, with up to 20% reduction of the EOF. The process is reversible, and removal of the light source results in a flow increase back to the original rate. The ability to alter flow rates in micro-fluidic channels using light has very significant implications, as it could dramatically simplify the manner in which micro-flow systems are controlled.