Search

Abstract: A microelectromechanical systems (MEMS) thermal flow sensing array constructed of biocompatible materials has been designed, fabricated, and tested. In addition to the construction, the electronic biasing conditions were selected such that sensor operation was compatible with biological fluids. The device comprises several thin film platinum sensing elements sandwiched in a Parylene C membrane. The membrane is suspended over a bulk-micromachined silicon channel for improved thermal isolation. This sensing array layout permits, for the first time, operation in multiple flow sensing modes using a single device. Multi-mode testing was performed in hot-film, calorimetric, and time-of-flight modes at low overheat ratios. Furthermore, constant current (CC) and constant temperature (CT) biasing methods were explored in hot-film mode. The results of the various testing modes were compared and flow sensing down to 0.5μL/min has been demonstrated. [Copyright &y& Elsevier]

We present an implantable micropump with a miniature form factor and completely wireless operation that enables chronic drug administration intended for evaluation and development of cancer therapies in freely moving small research animals such as rodents. The low power electrolysis actuator avoids the need for heavy implantable batteries. The infusion system features a class E inductive powering system that provides on-demand activation of the pump as well as remote adjustment of the delivery regimen without animal handling. Micropump performance was demonstrated using a model anti-cancer application in which daily doses of 30 μL were supplied for several weeks with less than 6% variation in flow rate within a single pump and less than 8% variation across different pumps. Pumping under different back pressure, viscosity, and temperature conditions were investigated; parameters were chosen so as to mimic in vivo conditions. In benchtop tests under simulated in vivo conditions, micropumps provided consistent and reliable performance over a period of 30 days with less than 4% flow rate variation. The demonstrated prototype has potential to provide a practical solution for remote chronic administration of drugs to ambulatory small animals for research as well as drug discovery and development applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the design, fabrication, and functional testing of a fully implantable, flexible, Parylene-enable neurostimulator that features single-channel wireless stimulation capability . This system comprises a fold-and-bond microelectromechanical systems (MEMS) coil for wireless power and data transmission, a BION 1-3 CMOS stimulator chip, discrete capacitors, as well as a carrier substrate with two platinum stimulating electrodes and interconnections for system assembly. The physical geometries of the devices are designed for use in retinal implantation with the specifications determined from the implantation results in canine eyes. The coil and carrier substrate are separately fabricated using a Parylene–metal skin technology. The unique properties of Parylene C allow these MEMS devices to be flexible and biocompatible, facilitating surgical procedure. The system assembly is achieved by interconnecting individual components together on the carrier substrate with a biocompatible silver epoxy. A 10μm layer of Parylene C is selectively deposited on the integrated system to protect it from corrosive eye environment. The system functionality is verified using a telemetry link setup, and single-phase pulses with amplitudes ranging from 7 to 8.5V are detected. [Copyright &y& Elsevier]

Abstract: A microelectromechanical systems (MEMS) drug delivery device is investigated for the treatment of incurable ocular diseases. Unlike conventional ocular drug delivery devices, this MEMS device is capable of being refilled, features electronic control of the drug regimen, and enables targeted intraocular drug delivery. The refillable design permits long-term drug therapy and avoids repetitive surgeries. Electronic control of dosing is achieved by using electrolysis-actuated pumping to deliver pharmaceuticals directly to the intraocular space. A flexible Parylene transscleral cannula allows targeted delivery to tissues in both the anterior and posterior segments of the eye. This electrochemically driven drug delivery device was demonstrated to provide flow rates suitable for ocular drug therapy (pL/min to μL/min). Both continuous and bolus drug delivery modes were performed to achieve accurate delivery of a target volume of 250nL. An encapsulation packaging technique was developed for acute surgical studies and preliminary ex vivo drug delivery experiments in porcine eyes were performed. [Copyright &y& Elsevier]