UBC Theses and Dissertations

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UBC Theses and Dissertations

MEMS-enabled drug delivery through wirelessly controlled pumping and valving actuation Yang, Ryan


Commercialised drug delivery devices (DDD) have enhanced healthcare treatments. The two main types of devices are active and passive drug releasing. Active release devices allow for more control and patient-customised treatments, but often require a battery as a power source, which accounts for a large portion of the size of the device. Passive release devices can have a larger holding reservoir, but do not offer the ability to tailor treatments. In both kinds of devices, reducing leakage is a challenge. This thesis presents a proof-of-concept test prototype of the implantable DDD that allows for active drug release that can be wirelessly powered. The prototype also has two actuators that enable simultaneous pumping and valving of the active drug release mechanism to meet the leakage challenge. An inductor-capacitor (LC) circuit patterned on a copper-clad polyimide sheet, using photolithography technique, acts as a wireless heat source. This LC circuit is activated with a radio frequency (RF) electromagnetic signal. At resonance, the inductor will heat up and this thermal energy then induces a displacement in the shape memory alloy (SMA) actuators. The SMA actuators are cantilevers that have been deposited with a SiO₂ stress layer which resets its position at room temperature. With the thermal energy, the SMA cantilevers undergo a change in crystal phase that result in a displacement of between 50-60 µm and exerts a force of about 170 mN. This actuation is applied onto a microfluidic chamber made of Parylene-C to force a release of drug from the pumping chamber. Another cantilever that acts in the opposite direction is attached onto an outlet channel. This cantilever acts as a pinch valve which when simultaneously heated, will allow flow out of the channel. Experimental testing of this prototype has shown single release volume of about 72 nL. A leakage comparison between attaching the valving cantilever and without is also shown. This prototype seeks to reduce leakage while still functioning as a wirelessly actuated active release implant through the novel design of dual cantilevers that can simultaneously pump and valve within the same LC circuit heat source.

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