Flexible Strain Sensor based on Printed LC Tank on Electrospun Piezoelectric Nanofibers

his work presents a screen-printed LC resonant tank-based strain sensor. The resonant tank consists of a planar inductor and an interdigitated capacitor connected in parallel. The inductor was screen printed on flexible polyamide substrate and the capacitor is printed on the piezoelectric Poly-L-lactide (PLLA) nanofibers obtained by electrospinning. The resonant frequency of the tank is tuned for ~13.56 MHz. The inductors and capacitors were characterized using an impedance analyzer to evaluate the frequency characteristic of both. As the interdigitated capacitor is realized on a piezoelectric substrate the permittivity and hence the capacitance varies with the application of dynamic pressure. For the dynamic pressure, less than 2 kPa the sensitivity S 1 is 8.55 kPa -1 . The sensitivities in the range of 2-4 kPa -1 and 4-7 kPa -1 are calculated as S 2 = 31.27 kPa -1 and S 3 = 8.61 kPa -1 respectively. The fabricated flexible sensor shows the potential for wearable applications such as sub-bandage pressure monitoring while also exploiting the piezoelectric properties of PLLA to accelerate the wound healing through electrical stimulation

Graphene Based Low Voltage Field Effect Transistor Coupled with Biodegradable Piezoelectric Material Based Dynamic Pressure Sensor

Pressure sensors form the basic building block for realization of an electronic or tactile skin used in prothesis, robotics, and other similar applications. This paper presents a device consisting of biodegradable piezoelectric material based dynamic pressure sensor coupled with a graphene field-effect-transistor (GFET) operated at very low voltage (50 mV). The device has a biodegradable β-glycine/chitosan composite based metal–insulator–metal (MIM) structure connected with GFET in an extended gate configuration. The developed device shows a sensitivity of 2.70 × 10–4 kPa–1 for a pressure range of 5–20 kPa and 7.56 × 10–4 kPa–1 for a pressure range between 20 and 35 kPa. A distinctive feature of the presented device is its very low operation voltage, which offers a significant advantage toward the development of energy efficient large-area electronic skin. Further, the biodegradability of piezoelectric material makes the presented sensors useful in terms of reduced electronic waste, which is currently another growing area of interest

Porous Elastomer based Soft Pressure Sensor for Autonomous Underwater Vehicles

This work presents a soft capacitive pressure sensor fabricated by sandwiching a porous elastomeric dielectric layer between two electrodes on flexible polyimide (Kapton) substrate. The fabricated sensor was tested over a wide pressure sensing range (0-300 kPa), similar to pressures experienced up to approx. 30m below the sea level. In this range, the sensor presented a near-linear response (94.5%) and a sensitivity of 0.0007 kPa −1 . The sensor also featured fast response and recovery times (0.8 s and 1.2 s, respectively), as well as good repeatability and stability - thus proving its applicability for a wide range of pressure sensing applications, particularly underwater robotics for real-time monitoring and surveillance operations

Soft Robotic Finger with Integrated Stretchable Strain Sensor

This work presents an advanced soft robotic finger with integrated strain sensor based on carbon nanotubes (CNTs). The interdigitated strain sensor is obtained by dielectrophoretic assembled CNT network. The sensor is connected to stretchable interconnects to ensure robust electrical connection during movements of the soft finger. The sensor is highly sensitive with up to 1300% change in the resistance for 11% strain. Finally, the CNT strain sensor is integrated with a soft robotic finger to monitor the bending for real time kinesthetic tactile feedback

Bio-Organic Glycine Based Flexible Piezoelectric Stress Sensor for Wound Monitoring

The application of controlled mechanical stress on a wound site can accelerate the wound healing by improving the cellular proliferation during tissue regeneration. To facilitate this there is need to monitor the applied stress around the wound site and hence there is need to develop a biocompatible stress sensor. Here we present the glycine-based biocompatible and flexible piezoelectric stress sensor. The sensor is based on novel piezoelectric composite comprising of piezoelectric y-glycine micro-crystals embedded in PDMS. On application of external force the sensor generates an average output voltage of 250 mV, with current density of 0.010 μA/cm 2 and a power density of 2.5 nW/cm 2 . While the produced piezoelectric voltage helps accelerate the wound healing, the energy generation by the sensor could also find potential applications in self-powered touch sensors. The successful demonstration of presented stress sensor, we will pave the way for their integration on compression bandages and dressings used for chronic wound management

Glycine–Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine-chitosan piezoelectric films. Fabricated by self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of stable spherulite structure of β-glycine (size varying from few millimetres to centimetre) embedded in amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms the formation of pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent casting method can be used to prepare a biodegradable β-glycine/chitosan based piezoelectric film with sensitivity (~ 2.82 ± 0.2 mV kPa−1) comparable to those of non-degradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range of 0.26 nF to 0.12 nF at a frequency range of 100 Hz and 1 MHz and its dielectric constant and the loss factor are 7.7 and 0.18 respectively in high impedance range under ambient conditions. The results suggest that glycine-chitosan composite is a promising new bio-based piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics