33,816 research outputs found
Temperature compensated tactile sensing using MOSFET with P(VDF-TrFE)/BaTiO3 capacitor as extended gate
This work presents Poly(vinylidene fluoride – trifluoroethylene))/Barium Titanate (P(VDF-TrFE)-BT) nanocomposite based touch sensors tightly coupled with MOSFET devices in extended gate configuration. The P(VDF-TrFE)-BT nanocomposite exploits the distinct piezo and pyroelectric properties of P(VDF-TrFE) polymer matrix and BT fillers to suppress the temperature response when force and temperature are varied simultaneously. The reasons for this unique feature have been established through structural and electrical characterization of nanocomposite. The proposed touch sensor was tested over a wide range of force/pressure (0-4N)/(0-364 Pa) and temperature (26-70°C) with almost linear response. The sensitivity towards force/pressure and temperature sensor are 670 mV/N/7.36 mV/Pa and 15.34 mV/°C respectively. With this modified touch sensing capability, the proposed sensors will open new direction for tactile sensing in robotic applications
Shape Memory Polymer Resonators as Highly Sensitive Uncooled Infrared Detectors
Uncooled InfraRed (IR) detectors have enabled the rapid growth of thermal
imaging applications. These detectors are predominantly bolometers, where the
heating of pixel from incoming IR radiation is read out as a resistance change.
Another uncooled sensing method is to transduce the IR radiation into the
frequency shift of a mechanical resonator. We present here a highly sensitive,
simple to fabricate resonant IR sensor, based on thermo-responsive Shape Memory
Polymers (SMPs). By exploiting the phase-change polymer as the transduction
mechanism, our approach provides 2 orders of magnitude improvement of the
temperature coefficient of frequency (TCF). The SMP has very good absorption in
IR wavelengths, obviating the need for an absorber layer. A Noise Equivalent
Temperature Difference (NETD) of 22 mK in vacuum and 112 mK in air are obtained
using f/2 optics. Such high performance in air eliminates the need for vacuum
packaging, paving a path towards flexible IR sensors
Tactile feedback display with spatial and temporal resolutions.
We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications
A flexible and highly sensitive pressure sensor based on a PDMS foam coated with graphene nanoplatelets
The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams loaded with multilayer graphene nanoplatelets (MLGs) for application as high sensitive piezoresistive pressure sensors. The effective DC conductivity of the produced foams is measured as a function of MLG loading. The piezoresistive response of the MLG-PDMS foam-based sensor at different strain rates is assessed through quasi-static pressure tests. The results of the experimental investigations demonstrated that sensor loaded with 0.96 wt.% of MLGs is characterized by a highly repeatable pressure-dependent conductance after a few stabilization cycles and it is suitable for detecting compressive stresses as low as 10 kPa, with a sensitivity of 0.23 kPa−1, corresponding to an applied pressure of 70 kPa. Moreover, it is estimated that the sensor is able to detect pressure variations of ~1 Pa. Therefore, the new graphene-PDMS composite foam is a lightweight cost-effective material, suitable for sensing applications in the subtle or low and medium pressure ranges
Materials science and the sensor revolution
For the past decade, we have been investigating strategies to develop
ways to provide chemical sensing platforms capable of long-term
deployment in remote locations1-3. This key objective has been driven by
the emergence of ubiquitous digital communications and the associated
potential for widely deployed wireless sensor networks (WSNs).
Understandably, in these early days of WSNs, deployments have been
based on very reliable sensors, such as thermistors, accelerometers, flow
meters, photodetectors, and digital cameras. Biosensors and chemical
sensors (bio/chemo-sensors) are largely missing from this rapidly
developing field, despite the obvious value offered by an ability to measure
molecular targets at multiple locations in real-time. Interestingly, while
this paper is focused on the issues with respect to wide area sensing of
the environment, the core challenge is essentially the same for long-term
implantable bio/chemo-sensors4, i.e.; how to maintain the integrity of the
analytical method at a remote, inaccessible location
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Printed, Flexible Lactate Sensors: Design Considerations Before Performing On-Body Measurements.
This work reports the process of sensor development, optimization, and characterization before the transition to on-body measurements can be made. Sensors using lactate oxidase as a sensing mechanism and tetrathiafulvalene as a mediator were optimized for sporting applications. Optimized sensors show linear range up to 24 mM lactate and sensitivity of 4.8 μA/mM which normalizes to 68 μA*cm-2/mM when accounting for surface area of the sensor. The optimized sensors were characterized 3 different ways: using commercially available reference and counter electrodes, using printed reference and counter electrodes, and using a printed reference electrode with no counter electrode. Sensors intended for measuring sweat must be selective in the presence of sweat constituents. Thus, in addition to traditional characterization in pH 7.0 buffer, we characterized sensor performance in solutions intended to approximate sweat. Sensor performance in pH 7.0 buffer solution was not reflective of sensor performance in artificial sweat, indicating that further characterization is necessary between sensor measurement in pH 7.0 buffer and on-body measurements. Furthermore, we performed enzyme activity measurements and sensor measurements concurrently in five different salts individually, finding that while NH4Cl and MgCl2 do not affect enzyme activity or sensor performance in physiologically relevant ranges of salt concentration, NaCl concentration or KCl concentration decreases enzyme activity and sensor current. On the other hand, CaCl2 induced a nonlinear change in sensor performance and enzyme activity with increasing salt concentration
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