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A novel pressure transducer concept is introduced in which external pressure variations induce changes in the volume of a trapped microbubble ( \mu \textB ) in an electrolyte solution. These volumetric changes are monitored by electrochemical impedance-based measurements and may be used for pressure tracking applications. Microbubbles are nucleated on-demand by electrolysis within a confinement chamber with high precision (measured size RSD $\sim 1$ %). This pressure transducer concept was developed specifically for operation in liquid environments and features biocompatible construction, small footprint (<0.1 mm2), and low power consumption (<1 nW). This combination of features is ideal for in vivo pressure monitoring applications. [2015-0203] [ABSTRACT FROM PUBLISHER]

To investigate the mechanical interactions between the implanted cortical multielectrode probes and brain tissue, a Parylene C-based electrochemical-microelectromechanical systems force sensor array was developed. The array consists of seven linearly distributed sensor units arranged along the length of a flexible Parylene C microchannel. The seven sensor units are formed by eight fluidically coupled and adjacent platinum electrode pairs enclosed within the microchannel. Deformation of the top surface of the mechanically compliant microchannel changes the volumetric conduction path between the pairs of sensing electrodes, and therefore, the measured electrochemical impedance, which is proportional to the magnitude of the contacting force. Each sensor unit demonstrated a linear response from 0 to 60 mN with a sensitivity of 0.13 ± 0.01 percentage change in impedance/ \mu \textN (%/ \mu \textN ; mean ± SE, n = 6 ). The sensor arrays were mounted onto a ceramic intracortical probe and inserted into the tissue phantoms to verify in situ functionality and assess interfacial probe mechanics. Probe surface force distribution was measured under various insertion speeds and the results indicated that interfacial forces are distributed nonuniformly along the probe shaft length, concentrating within the first 1 mm of the advancing probe tip. Faster insertion speeds were also found to decrease the magnitude of the interfacial forces, suggesting that the tissue strain during cortical implantation may be minimized through appropriate selection of the insertion speed.[2014-0320] [ABSTRACT FROM PUBLISHER]

We report on the use of electrochemical impedance (EI) as the basis for force transduction in Parylene-based microdevices. Electrolyte-filled microstructures were realized for extremely sensitive contact-force detection (10 mN range, \pm0.023 mN resolution) enabled by EI-based transduction and are a promising platform for next-generation biomedical sensing technology. The design, fabrication, and characterization of Parylene-based electrochemical-MEMS (EC-MEMS) devices capable of microNewton contact-mode force measurement are presented and discussed.\hfill[2011-0040] [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and characterization of electrochemical microelectromechanical systems (EC-MEMS) devices featuring encapsulated fluid as the basis for transduction. Parylene microstructures, including discrete chambers (square or circular geometry), are utilized as physical transducers for electrochemically mediated liquid impedance transduction of physical phenomenon such as contact and force. Parylene-based EC-MEMS technologies uniquely leverage advantages in size (<500\ \mu\m diameter), packaging (no hermetic packaging necessary), power (nanowatts to microwatts), and flexibility to address the physical sensing requirements of in vivo applications. Robust EC impedance (EI) sensor responses (up to 20% from base-line) and discrimination of 200-nm chamber deflections were possible using the EI transduction technique. Additional transducer configurations enabling electrolysis-based out-of-plane actuation and biomimetic mechanotransduction in microfluidic channels are also presented. \hfill[2010-0157] [ABSTRACT FROM AUTHOR]