Terahertz spectroscopy and spectral imaging

Over recent years, terahertz wavelengths (over 0.1-10 THz frequencies) have contributed strongly to spectroscopy and imaging in Biomedical Engineering. Terahertz radiation is sensitive to the vibrational and rotational modes of biomolecules, making it ideal for identifying chemical signatures. Additionally, terahertz radiation is non-ionizing and safer than other frequencies (e.g., x-rays). Given these motivations, there is significant interest in the generation and detection of terahertz radiation. However, current terahertz time-domain spectroscopy systems have challenges related to dynamic range and acquisition time. The Collier Research Group has developed a terahertz time-domain spectroscopy system that makes use of Kalman filtering to produce high dynamic range measurements with short acquisition time.

A related spectral imaging technology is hyperspectral imaging, whereby wavelength information (over the visible spectrum) for a line of pixels is stored on a two-dimensional sensor. An image is then scanned line-by-line. The Collier Research Group has made advancements in snapshot hyperspectral imaging, whereby the full image can be stored instantly. Such advancements come about through strategic implementation of Fourier analyses.

Microfluidic systems in agri-food and biomedical

Lab-on-a-chip systems have revolutionized the biomedical device industry and Biomedical Engineering. These microsystems allow high throughput analyses of biofluids for diagnostics and scientific pursuits. Traditionally, these systems are continuous-flow-based and make use of micropumps, microvalves, and other components. The Collier Research Group has developed a Microchip Capillary Electrophoresis device that can detect antibiotics in dairy milk.

A reconfigurable form of microfluidics has emerged whereby microdroplets are actuated on a two-dimensional planar structure using electric fields. These systems are Digital Microfluidic devices. The Collier Research Group investigated such Digital Microfluidic devices and produced multiplexed systems whereby individual microdroplets are actuated with a trinary activation algorithms and sensed through integration of fibre-optic cables. This multiplexed system has been integrated with optical and terahertz spectroscopy techniques. The Collier Research Group has also developed digital microfluidic platforms for potential use in polymerase chain reaction. Here, enhanced infrared annealing is achieved through total internal reflection of an optical beam.

Optofluidic elements

There is great potential in optofluidic lenses. Such lenses use the refractive properties of fluid for focusing and magnification of light. A liquid lens has advantages over a fixed lens in that its optical properties (e.g., focal length) can be adapted in real-time. Therefore, adaptive optofluidic lenses are sought after in beam steering applications and on-chip integration. Further applications include free-space optical communication devices and remote sensing requiring high field-of-view.

The Collier Research Group has developed optofluidic lenses. These lenses are able to create subunit aspect ratio lenses and have been implemented in closed systems with mechanical tuning for in-plane focusing and low-voltage operation.