A MEMS electrochemical bellows actuator for fluid metering applications.

We present a high efficiency wireless MEMS electrochemical bellows actuator capable of rapid and repeatable delivery of boluses for fluid metering and drug delivery applications. Nafion®-coated Pt electrodes were combined with Parylene bellows filled with DI water to form the electrolysis-based actuator. The performance of actuators with several bellows configurations was compared for a range of applied currents (1-10 mA). Up to 75 boluses were delivered with an average pumping flow rate of 114.40 ± 1.63 µL/min. Recombination of gases into water, an important factor in repeatable and reliable actuation, was studied for uncoated and Nafion®-coated actuators. Real-time pressure measurements were conducted and the effects of temperature, physiological back pressure, and drug viscosity on delivery performance were investigated. Lastly, we present wireless powering of the actuator using a class D inductive powering system that allowed for repeatable delivery with less than 2 % variation in flow rate values.

An implantable MEMS micropump system for drug delivery in small animals.

We present the first implantable drug delivery system for controlled timing and location of dosing in small animals. Current implantable drug delivery devices do not provide control over these factors nor are they feasible for implantation in research animals as small as mice. Our system utilizes an integrated electrolysis micropump, is refillable, has an inert drug reservoir for broad drug compatibility, and is capable of adjustment to the delivery regimen while implanted. Electrochemical impedance spectroscopy (EIS) was used for characterization of electrodes on glass substrate and a flexible Parylene substrate. Benchtop testing of the electrolysis actuator resulted in flow rates from 1 µL/min to 34 µL/min on glass substrate and up to 6.8 µL/min on Parylene substrate. The fully integrated system generated a flow rate of 4.72 ± 0.35 µL/min under applied constant current of 1.0 mA while maintaining a power consumption of only ~3 mW. Finally, we demonstrated in vivo application of the system for anti-cancer drug delivery in mice.

Silver nanosystems for photoacoustic imaging and image-guided therapy.

Due to their optical absorption properties, metallic nanoparticles are excellent photoacoustic imaging contrast agents. A silver nanosystem is presented here as a potential contrast agent for photoacoustic imaging and image-guided therapy. Currently, the nanosystem consists of a porous silver layer deposited on the surface of spherical silica cores ranging in diameter from 180 to 520 nm. The porous nature of the silver layer will allow for release of drugs or other therapeutic agents encapsulated in the core in future applications. In their current PEGylated form, the silver nanosystem is shown to be nontoxic in vitro at concentrations of silver up to 2 mgml. Furthermore, the near-infrared absorbance properties of the nanosystem are demonstrated by measuring strong, concentration-dependent photoacoustic signal from the silver nanosystem embedded in an ex vivo tissue sample. Our study suggests that silver nanosystems can be used as multifunctional agents capable of augmenting image-guided therapy techniques.