This paper describes the application of laser micromachining techniques for the fabrication of microfluidic channels in low temperature co-fired ceramic, LTCC, technology. It is shown that embedded cavities can be successfully realised by employing a recently proposed progressive lamination process with no additional fugitive material. Various microfluidic structures have been fabricated and X-ray imaging has been used to assess the quality of the embedded channels after firing. The problem of achieving accurate alignment between LTCC layers is addressed such that deeper channels, spanning more than one layer, can be fabricated using a pre-lamination technique. A number of possible applications for the presented microfluidic structures are discussed and an H-filter particle separator in LTCC is demonstrated.

We report on hard-field tomography measurements in the THz spectral range and subsequent image reconstruction of a phantom subject. At THz wavelengths, the traditional hard-field tomography approach to measure attenuation is hindered by a substantial diffusely scattered component. Consequently, we work in optical density image contrast, as opposed to material density typical in high-energy hard-field modalities, such as X-ray CT. The hard-field component of the signal is extracted with a spatial filter, efficiently suppressing the soft-field contributions from the imaged subject. Using time-domain THz spectroscopy, line integrals of the real part of the refractive index are taken, by measuring the delay of the THz pulse across the subject at 12 angles and 0.5 mm steps in the transversal direction for each angle. The delay values are calculated from the location of the first peak in the integrated time-domain waveforms. This is justified by the physics of THz generation with ultrashort pulses in a biased-gap antenna and is shown to be superior to existing alternatives. The resulting tomography projections provide evidence for the hard-field character of the line integrals. The quality of the reconstructed image is interpreted and discussed, together with some limitations and future avenues.

We demonstrate the use of a full-wave electromagnetic field simulator to verify terahertz (THz) transmission-mode spectroscopic measurements of periodic arrays containing subwavelength cylindrical scatterers. Many existing THz scattering studies utilize analytical solutions, which were developed for a single scatterer. For multiple scatterers, a scaling factor equal to the number of scatterers is applied, accounting for interference between far-field radiative contributions from those scatterers but not their near-field mutual coupling. Consequently, analytical solutions do not accurately verify measurements. Conversely, results from the full-wave electromagnetic field simulator elucidate our measurements well, and provide an important insight into how the scattering behavior of cylindrical scatterers is influenced by test conditions.

We report on tomographic measurements in the terahertz spectral range and subsequent image reconstruction of a phantom subject. At terahertz wavelengths we abandon the traditional hard-field tomography approach to use attenuation measurements for imaging, because of the strong beam steering at the periphery of objects and the existence of a substantial diffusely scattered component. Under these conditions we focus on imaging from the measurements of the terahertz pulse propagation delay, taken with a system for time-domain terahertz spectroscopy, and reconstruct the subject's optical density instead of e.g. material density as in x-ray tomography. The novelty is our experimental approach to retain, by spatial and temporal filtering, only the photons that propagate along the shortest straight paths allowing hard-field tomography, approach for the image reconstruction. We show that pulse delay measurements result in path integrals of the light's group velocity in the subject and therefore the image reconstruction yields the spatial distribution of the real part of the refractive index. Furthermore, we suggest a procedure whereby the pulse delay time is calculated from the time-domain waveform with a better precision, taking into account the physics of THz generation by ultrashort pulses in a biased-gap antenna.

Thin films of barium strontium titanate (BST), lanthanum modified bismuth titanate (LBT) and lead zirconate titanate (PZT) were fabricated by sol-gel methods onto sapphire substrates. They were transferred to a second substrate by using UV eximer laser radiation to delaminate the films from the fabrication substrate. Scanning electron microscopy revealed melting at the interfacial region of the LBT and PZT films, thus providing the delamination mechanism, but melting was not observed in the BST films. Only the PZT film, after laser transfer, retained its ferroelectric properties, with remnant polarisation of similar to 30 mu C/cm(2), and a high coercive field of 150 kV/cm.

We have performed 2-dimensional tomographic measurements upon shaped phantoms constructed from material with low optical power, using a time-domain THz arrangement. While the phantom morphology can be successfully reconstructed using the time-delay data, use of the THz pulse amplitude is less reliable, demonstrating distortions that may be a consequence of beam diffraction effect. This effectively masks the true attenuation contrast of the object.

Scattering of terahertz radiation from cylindrical strands is explored as a means of studying the effects of hair on the results of bio-tissue analysis. Strands of fiberglass are aligned either parallel or perpendicular to the polarization vector of the incoming terahertz beam. Spectroscopic results reveal that the materialpsilas intrinsic THz transmission properties are highly dependent on fiber orientation.

Thick films of 0.7BiFeO3–0.3PbTiO3 have been deposited on sapphire substrates by tape casting and sintering at 1000°C. Films 20μm in thickness were released from the fabrication substrate using KrF pulsed laser radiation, and epoxy bonded to platinized silicon substrates in order to demonstrate the low-temperature integration possibilities of xBiFeO3–(1−x)PbTiO3 films. Despite structural changes at the laser-released film interface, strain-electric field loops are typical of a ferroelectric, showing an ultimate strain of 0.09%. X-ray diffraction and scanning electron microscopy observations suggest that interfacial melting and migration of Bi2O3 is involved in the lift-off process.

The design, simulation and fabrication of high-Q zipping MEMS varactors is presented. A novel, stable zipping design allows continuous tuning as well as a large tuning range. High quality factors can be obtained using gold electrodes in order to minimise series resistance. By incorporating a high-permittivity dielectric in the varactor, the tuning range can be greatly increased and at the same time, the device size can be reduced. A fabrication process has been developed, including pre-stressed layers to provide the initial curvature, and this has been demonstrated up to and including transfer and bonding of the top electrodes from a carrier wafer.

Preferential binding of F-actin to lipid bilayers containing ponticulin was investigated on both planar supported bilayers and on a cholesterol-based tethering system. The transmembrane protein ponticulin in Dictyostelium discoideum is known to provide a direct link between the actin cytoskeleton and the cell membrane ( Wuestehube, L. J. ; Luna, E. J. J. Cell Biol. 1987, 105, 1741- 1751 ). Purification of ponticulin has allowed an in vitro model of the F-actin cytoskeletal scaffold system to be formed and investigated by AFM, epi-fluorescence microscopy, surface plasmon resonance (SPR), and quartz crystal microbalance with dissipation (QCM-D). Single filament features of F-actin bound to the ponticulin containing lipid bilayer are shown by AFM to have a pitch of 37.3 +/- 1.1 nm and a filament height of 7.0 +/- 1.6 nm. The complementary techniques of QCM-D and SPR were used to obtain dissociation constants for the interaction of F-actin with ponticulin containing bilayers, giving 10.5 +/- 1.7 microM for a physisorbed bilayer and 10.8 +/- 3.6 microM for a tethered bilayer, respectively.

The design and performance of a simple and compact far-infrared Fourier transform spectrometer is described. The spectrometer works as a Michelson interferometer without a beam splitter, and uses a Golay cell or a pyroelectric sensor for detection. A pair of flat lamellar mirrors with a computer-controlled displacement introduces a precisely defined phase difference between two parallel beams of nearly equal radiated power. The interferometer is intended for operation at frequencies between 0.1 and 3 THz with a frequency resolution of 6 GHz, and is used to characterize both continuous-wave and pulsed terahertz emitters, as well as different terahertz detectors.

We observe that the intensity of water vapour absorption lines in a combustion system containing a diffusion flame is highly dependent on the air flow rate. This implies that the recorded signal originates from (lower temperature) water vapour outside the volume of the flame. Seeding the flame enables water to be used as a fuel region marker.

Terahertz (THz) time-domain spectroscopy (TDS) is used to study two types of amorphous materials: glasses and polymers. The theory of far-infrared (IR) absorption in amorphous materials is used to analyse the results, and to understand the differences in THz absorption among the sample materials. A family of related borosilicate glasses has been examined along with silica glass, and their THz absorption coefficients and refractive indices are compared. Two chalcogenide glasses are also studied. Three types of polymer plates have been examined, and their THz transmission properties are compared with those of glasses. Polymerisation in SU8 films has been studied by exposing samples to UV for different lengths of time and comparing their THz transmission properties.

Terahertz time-domain spectroscopy is used to study properties of nonpolar amorphous materials. Terahertz absorption spectra and refractive indices were measured in a number of glasses, lubricating oils, and polymers, and the results were correlated with material properties.

Diffuse reflectance spectroscopy in the visible and NIR is widely used to measure complex dielectric constants of highly scattering opaque materials. Compared with specular reflectance measurements, it has the advantages of low sensitivity to sample position and surface preparation, and improved accuracy in the determination of optical constants. We extend this technique to the THz range, describing the design and performance of a THz diffuse reflectance system.

A series of gold nanoparticles stabilized by the adsorption of heterocyclic mercaptan derivatives, including 2-mercaptopyridine (2MPy), 2-mercaptopyrimidine (2MPm) and 4-mercaptopyridine (4MPy), were synthesized and characterized by TEM, FTIR, UV-vis, and XPS. The adsorption of 2MPy molecules led to the most stable and uniform nanoparticles. In contrast, the 4MPy-coated nanoparticles showed a strong tendency to form 3D aggregates, which is attributed to cross linking between sulfur groups on neighboring particles. FTIR and UV-vis spectroscopy were employed to study the chemical conformation of the heterocyclic molecules on the gold surface. Significant differences between the IR spectra of the functionalized nanoparticles and the free mercaptan molecules were observed. Interpretations of these IR spectra were achieved with the aid of ab initio calculations. We found that the "thione form" is predominant when the molecules are either in a polycrystalline state or in methanol solution; however, they are stabilized in the "thiol-like form" when adsorbed on the particles. The XPS spectra of the 2MPy nanoparticles showed narrow peaks with the expected peak position. In contrast, the peaks in the spectra of the 2MPm- and 4MPy-passivated nanoparticles were strongly shifted. Oxidization of the sulfur group was detected in the 4MPy-modified nanoparticles, indicating that some molecules were adsorbed onto the gold surface via their nitrogen groups.

This paper introduces the field of all-optical signal processing at microwave frequencies, in which optical fibre networks are used to realise signal processing functions. The fundamental principles are explained, and the components of these structures described. An analysis of basic film structures, which can be used as building blocks for more complicated structures, is included with supporting measurements. Finally a new algorithm for the synthesis of window responses using an all-passive network is explained and demonstrated