6 research outputs found
MEMS micro-contact printing engines
This thesis investigates micro-contact printing (µCP) engines using micro-electro-mechanical
systems (MEMS). Such engines are self-contained and do not require further optical
alignment and precision manipulation equipment. Hence they provide a low-cost and
accessible method of multilevel surface patterning with sub-micron resolution. Applications
include the field of biotechnology where the placement of biological ligands at well
controlled locations on substrates is often required for biological assays, cell studies and
manipulation, or for the fabrication of biosensors.
A miniaturised silicon µCP engine is designed and fabricated using a wafer-scale MEMS
fabrication process and single level and bi-level µCP are successfully demonstrated. The
performance of the engine is fully characterised and two actuation modes, mechanical and
electrostatic, are investigated. In addition, a novel method of integrating the stamp material
into the MEMS process flow by spray coating is reported.
A second µCP engine formed by wafer-scale replica moulding of a polymer is developed to
further drive down cost and complexity. This system carries six complementary patterns and
allows six-level µCP with a layer-to-layer accuracy of 10 µm over a 5 mm x 5 mm area
without the use of external aligning equipment. This is the first such report of aligned
multilevel µCP.
Lastly, the integration of the replica moulded engine with a hydraulic drive for controlled
actuation is investigated. This approach is promising and proof of concept has been provided
for single-level patterning
Radio-frequency microplasmas with energies suited to in situ selective cleaning of surface adsorbates in ion microtraps
We have demonstrated a capacitively-coupled, radio-frequency (RF) microplasma inside the 3D electrode structure of an ion microtrap device. For this work, devices with an inter-electrode distance of 340 μm were used. The microplasmas were operated at Ω RF /2π = 23 MHz, in both He and He:N2 gas mixtures, over a range of RF amplitudes (140–220 V) and pressures (250–910 mbar). Spectroscopic analysis of the He I 667 nm and Hα 656 nm emission lines yielded the gas temperature and electron density, which enabled calculation of the mean ion bombardment energy. For the range of operating parameters studied, we calculated mean He+ energies to be between 0.3 and 4.1 eV. While these energies are less than the threshold for He sputtering of hydrocarbon adsorbates on Au, we calculate that the high energy tail of the distribution should remove adsorbate monolayers in as little as 1 min of processing. We also calculate that the distribution is insufficiently energetic to have any significant effect on the Au electrode surface within that duration. Our results suggest that the microplasma technique is suited to in situ selective removal of surface adsorbates from ion microtrap electrodes
A micro-optical module for multi-wavelength addressing of trapped ions
The control of large-scale quantum information processors based on arrays of
trapped ions requires a means to route and focus multiple laser beams to each
of many trapping sites in parallel. Here, we combine arrays of fibres, 3D
laser-written waveguides and diffractive microlenses to demonstrate the
principle of a micro-optic interconnect suited to this task. The module is
intended for use with an ion microtrap of 3D electrode geometry. It guides ten
independent laser beams with unique trajectories to illuminate a pair of
spatially separated target points. Three blue and two infrared beams converge
to overlap precisely at each desired position. Typical relative crosstalk
intensities in the blue are and the average insertion loss
across all channels is dB. The module occupies times less
volume than a conventional bulk-optic equivalent and is suited to different ion
species
Optothermal profile of an ablation catheter with integrated microcoil for MR-thermometry during Nd:YAG laser interstitial thermal therapies of the liver-An in-vitro experimental and theoretical study
PURPOSE: Flexible microcoils integrated with ablation catheters can improve the temperature accuracy during local MR-thermometry in Nd:YAG laser interstitial thermal therapies. Here, the authors are concerned with obtaining a preliminary confirmation of the clinical utility of the modified catheter. They investigate whether the thin-film substrate and copper tracks of the printed coil inductor affect the symmetry of the thermal profile, and hence of the lesion produced. METHODS: Transmission spectroscopy in the near infrared was performed to test for the attenuation at 1064 nm through the 25 μm thick Kapton substrate of the microcoil. The radial transmission profile of an infrared high-power, light emitting diode with >80% normalized power at 1064 nm was measured through a cross section of the modified applicator to assess the impact of the copper inductor on the optical profile. The measurements were performed in air, as well as with the applicator surrounded by two types of scattering media; crystals of NaCl and a layer of liver-mimicking gel phantom. A numerical model based on Huygens–Fresnel principle and finite element simulations, using a commercially available package (COMSOL Multiphysics), were employed to compare with the optical measurements. The impact of the modified optical profile on the thermal symmetry was assessed by examining the high resolution microcoil derived thermal maps from a Nd:YAG laser ablation performed on a liver-mimicking gel phantom. RESULTS: Less than 30% attenuation through the Kapton film was verified. Shadowing behind the copper tracks was observed in air and the measured radial irradiation correlated well with the diffraction pattern calculated numerically using the Huygens–Fresnel principle. Both optical experiments and simulations, demonstrate that shadowing is mitigated by the scattering properties of a turbid medium. The microcoil derived thermal maps at the end of a Nd:YAG laser ablation performed on a gel phantom in a 3 T scanner confirm that the modified irradiation pattern does not disrupt the thermal symmetry, even though, unlike tissue, the gel is minimally scattering. CONCLUSIONS: The results from this initial assessment indicate that microcoils can be safely integrated with ablation catheters and ensure that the complete necrosis of the liver tumor can still be achieved