Dr. Tharshan C. Vaithianathan Profile

Dr. Tharshan C. Vaithianathan

at Univ of South Australia

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Proceedings Article | 14 December 2006 Paper

An electrically controlled micromachined drug delivery device employing two silicon wafers

Robin Rajan, Syed Mahfuzul Aziz, Tharshan Vaithianathan

Proceedings Volume 6416, 64160P (2006) https://doi.org/10.1117/12.695644

KEYWORDS: Silicon, Semiconducting wafers, Gold, Oxides, Etching, Glasses, Photomasks, Chromium, Photoresist materials, Metals

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There is constant interest and research being conducted in devising new means to deliver drugs to the internal organs of the human body to overcome the shortcomings of conventional systems. In this paper we propose a micro fabricated drug delivery system capable of storing drugs in the range of micro-litres (μL) in its secondary reservoir. It will deliver drugs by electrochemical disruption of thin gold membranes. This device is proposed to be integrated in an endoscopic capsule with a view to deliver drugs in areas that are difficult to access, such as the small and large intestines. The design of the device is based on two microfabricated silicon wafers having multiple cavities etched into them. The cavities on the silicon wafers are covered by thin gold membranes. These membranes act as the openings for the release of drugs stored in a secondary reservoir sandwiched between the two silicon wafers. The secondary reservoir is being named so because the cavities in the silicon wafer act as the primary reservoir. The secondary reservoir having holes made in them can be made to align with cavities on the silicon wafers and bonded. On applying suitable voltage, the gold membranes disrupt electrochemically, providing outlets from both sides. The drug diffuses out from both ends of the device.

Proceedings Article | 29 July 2003 Paper

Functional imaging of the brain using a portable NIR instrument

Tharshan Vaithianathan, Iain Tullis, Nicholas Everdell, Terence Leung, Judith Meek, David Delpy

Proceedings Volume 4955, (2003) https://doi.org/10.1117/12.478168

KEYWORDS: Light emitting diodes, Photodiodes, Palladium, Sensors, Near infrared, Brain, Optical amplifiers, Silicon, Head, Neuroimaging

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Near Infrared Spectroscopy (NIRS) is a powerful method for non-invasive mapping of cerebral functional activation. We have developed an NIRS instrument that is portable, inexpensive and lightweight consisting of an array of light emitting diodes (LEDs) and photodiodes (PDs) mounted on a flexible printed circuit board (PCB). The flexibility and portability of the instrument makes it easy to apply to subjects ranging from premature babies in intensive care to adults. The flexible PCB array consists of 48 LEDs operating at two different wavelengths (780nm & 880nm) together with 14 photodiodes. Transimpedence amplifiers for each of the PDs are located on the flexible pad to minimise noise pick up. The LEDs are pulsed (10ms) at a peak optical power of 20mW, while a sample and hold circuit monitors the voltages at all of the PDs. The array is also encapsulated in black silicon rubber, except for the regions directly above the LED's and PD's, which have a clear silicone rubber cover. The sensor array is attached to the electronics by two one metre long flexible ribbon cables. The monitoring circuit provides medical grade electrical isolation between the patient and computer. Studies have been conducted on phantoms to test the penetration depth of the sensor array for two different separations of LEDs and PDs (11mm and 27mm). The maximum depths that can be probed are 5mm and 11mm respectively. This makes it suitable for studying cortical activation in babies.

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