The development of sensors for monitoring hazardous materials in security and environmental applications has been increasing in the last few years. In particular, organophosphates pose a serious health threat that affects the food and agriculture industries. Hence, their rapid on-site detection is highly desired, especially through remote robotic sampling that can minimize the exposure of humans to these hazardous chemicals. To handle sample collection, a robotic manipulator requires tactile feedback, to ensure that no damage will be done to either the robot or the other object in contact due to excessive force. To provide tactile feedback, porous polydimethylsiloxane pressure sensors based on a capacitive mechanism were chosen here, and integrated with enzyme-based electrochemical sensors specific for organophosphate compounds (e.g. methyl paraoxon). This results in a hybrid physical-chemical sensing glove that can simultaneously measure the pressure and chemical target without interference between the two sensors. Our pressure sensors showed 455% relative capacitance change per 10 kPa applied pressure, with an average sensitivity (S) of 0.057 AE 0.004 kPa À1 in the 3-20 kPa range and a maximum sensitivity of 0.30 AE 0.08 kPa À1 in the o0.05 kPa range. The chemical biosensors showed a detection range of 20-180 lM for methyl paraoxon in the liquid phase. We have thus combined low-cost chemical and pressure sensors together on disposable, retrofitting gloves, and demonstrated simultaneous tactile sensing and organophosphate pesticide detection in a point-of-use robotic field platform that is scalable, economical, and adaptable for different security, environmental, and food-safety applications.

An inkjet-printed inductor-capacitor (LC) resonator is demonstrated for wireless monitoring of pressure in aqueous environments. The sensing mechanism is based on a compressible capacitor that modulates the LC circuit resonant frequency depending on the applied pressure. The trace conductivity and geometric designs of inductors are improved to increase mutual inductive coupling between the sensor and the readout coil. The dielectric porosity in the capacitive sensors are tuned to enhance pressure sensitivity. The encapsulated sensor showed a linear response to pressure between 30 and 170 mmHg (4-23 kPa) with respect to atmospheric pressure and a resolution of 3 mmHg. The sensor temporal response is up to 6 Hz and capable of capturing typical heart-pulse waveforms as a proof-of-concept demonstration.

The effects of metal objects on the mutual inductance, self-inductance, and effective series resistance (ESR) of the coaxial coils of a transcutaneous energy transmission system (TETS) were investigated theoretically and experimentally. The theory considers a thin conducting sheet of infinite size aligned parallel to a current-carrying coil. Results of the theory indicate that coil parameters vary with the distance from the sheet to the coil. Changes in mutual and self inductance are independent of the conductivity and thickness of the sheet, with a larger percentage change for mutual inductance than for self inductance. Changes in ESR are proportional to the surface resistivity of the sheet. Experimental measurements using several aluminum sheets and a titanium alloy can in the presence of the TETS coils used for the Penn State artificial heart showed excellent agreement with the theory for inductance parameters and agreed within a factor of 2 for ESR measurements when skin effect was considered. It was generally observed that mutual inductance drops to 65% of its initial value as a metal sheet is moved to within 1-2 cm of the coil, while self-inductance drops to 80% of its initial value when the sheet is 2 cm from the coil. Measured changes in ESR tended to be higher than the calculated values with the discrepancy depending on distance to the metal object. Theory and measurements were extended to the case of lateral misalignment of the coils.