We report the design and operation of an optical fibre manometry catheter for measuring variation in pressure in the
oesophagus during peristalsis. Catheters of this kind are used to help diagnose oesophageal disorders by recording the
muscular contractions of the oesophageal wall in patients having difficulty swallowing. Traditional oesophageal
catheters consist of an array of recording sites enabling pressure measurement from multiple locations along the the
oesophagus. However, these catheters tend to be bulky or complex to operate whereas our optical equivalent uses a
series of Fibre Bragg Grating (FBG) pressure sensors on a single fibre; significantly reducing complexity and allowing
the catheter diameter to be minimised. The data from each FBG was recorded using a solid state spectrometer in which
the reflected peaks each covered a number of pixels of the spectrometer. This has enabled the FBG peaks to be tracked
in wavelength with sub-nanometre precision resulting in pressure sensitivities of less than 1mmHg. Results from a
clinical trial carried out on 10 healthy subjects will be presented. For the trial, each subject was simultaneously intubated
with the optical catheter and a commercially available solid-state catheter. Back-to-back readings were taken from both
devices during a series of controlled water swallows. Ten swallows were recorded with the catheters sensors positioned
in proximal, mid, and distal regions of the oesophagus and the data analysed statistically. The fibre optic device
accurately picked up the dynamic variations in pressure, and can react at least as fast as the solid state device.
We report the methodology and fabrication of α-Fe2O3 nanostructured photoelectrodes for water splitting applications. Thin films of α-Fe2O3 (hematite) were deposited onto nanostructured substrates (ZnO nanowires and TiO2 nanotubes) using filtered arc deposition (FAD). It is proposed that such nanostructured electrodes can overcome the poor absorption and high charge carrier recombination of planar α-Fe2O3 films used for water splitting. Results of the characterization and optimization of the α-Fe2O3 films and the nanostructured substrates are presented. The filtered arc deposition technique is shown to produce high purity α-Fe2O3 films. Results of preliminary studies of silicon doping of the hematite films are presented. The filtered arc deposition technique is shown to be suitable for coating highly structured substrates.
The short diffusion length of photo-excited charge carriers in Fe2O3 is one of the factors limiting the water splitting
efficiency of iron oxide based materials. To overcome this problem we are engineering transparent arrays of nanowires
to act as conducting substrates for the Fe2O3. To help understand the charge transport characteristics of the Fe2O3
component we report transient photocurrent measurements performed on an absorbing thin film of Fe2O3 deposited by
filtered arc deposition on conducting glass with a semi-transparent silver Schottky top contact. Ultraviolet laser pulses
were used to generate charge carriers near the surface and the resulting current transients were measured. A simulation
of this charge transport has also been developed. The sign of the observed transients was independent of applied bias,
consistent with a fully depleted film. The measurements also suggest that recombination may play a significant factor in
determining the transient shape. Further investigation is required to confidently predict mobilities.
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