John M. Maloney

Chronic, programmed polypeptide delivery from an implanted, multireservoir microchip device

Implanted drug delivery systems are being increasingly used to realize the therapeutic potential of peptides and proteins. Here we describe the controlled pulsatile release of the polypeptide leuprolide from microchip implants over 6 months in dogs. Each microchip contains an array of discrete reservoirs from which dose delivery can be controlled by telemetry.

Large-force electrothermal linear micromotors

Electrothermal linear micromotors fabricated by deep reactive ion etching of silicon-on-insulator wafers are presented. These high-aspect-ratio motors are powered by thermal actuator arrays with a height of 50 µm. Synchronized arrays, each containing ten actuators connected by a midpoint yoke, are used to advance a slider through frictional contact. Forces of 6.7 mN have been demonstrated at a voltage of 12 V using motors measuring 2.5 mm by 2.1 mm. Unidirectional motors have been successfully operated at speeds of up to 1 mm s−1 over a range in excess of 2 mm. Motors are found to be well suited for positioning compliant mechanisms and similar applications requiring large forces and displacements at low drive voltages.

In Vivo Biostability of CVD Silicon Oxide and Silicon Nitride Films

Low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) silicon oxide and silicon nitride films were implanted subcutaneously in a rat model to study in vivo behavior of the films. Silicon chips coated with the films of interest were implanted for up to one year, and film thickness was evaluated by spectrophotometry and sectioning. Dissolution rates were estimated to be 0.33 nm/day for LPCVD silicon nitride, 2.0 nm/day for PECVD silicon nitride, and 3.5 nm/day for PECVD silicon oxide. A similar PECVD silicon oxide dissolution rate was observed on a silicon oxide / silicon nitride / silicon oxide stack that was sectioned by focused ion beam etching. These results provide a biostability reference for designing implantable microfabricated devices that feature exposed ceramic films.