Dueck, B.; (2010) Robust optical diffractive technique to read out cantilever defl�ection. Doctoral thesis , UCL (University College London).

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Abstract

Microcantilevers have now been used successfully for over a decade. New assays are being developed and tested continuously but the technique has not arrived in hospitals and surgeries yet. The main obstacle was that a robust and reliable readout system which does not need intricate alignment before each measurement was not available. Therefore cantilever devices have only been used in university laboratories. The aim of the research presented in this thesis is to provide a diffractive optical readout for cantilever bending that is rapid, robust and easy to use. The diffractive readout discovered during my PhD involves a laser illuminating the entire cantilever and additionally parts of the chip base to which it is attached. The laser light diffracted from the cantilever contains information that allows a distinction to be made between tilting and bending of the cantilever. Additionally, measurements of the absolute tilting and bending can be performed and the time needed for aligning the cantilever chip in the laser beam is reduced to a minimum. This thesis describes the tools used to develop the diffractive readout and presents experimental results. First, a simulation was programmed to predict results and optimise experimental conditions. Second, an experimental setup was built from scratch and a new ow cell designed which was needed for transmission mode experiments. Third, test experiments in air were performed using a transmissive and a reflective diffraction approach. Fourth and finally, the applicability of the diffractive readout was shown by demonstrating that the binding of the antibiotic vancomycin to a glycopeptide could be measured successfully. I hope that the invention presented in this thesis will help to commercialise the cantilever setup and make it attractive for the use in hospital and surgeries speeding up diagnostic steps from days down to a few minutes. This thesis lays the cornerstone of the discovered, patented and tested optical diffractive readout technique for cantilever based biosensors. Optimisation of the experiment, being very important and essential, has to be focused on in the future and is not dealt with in detail in here.

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