Varij Panwar

Low voltage actuator using ionic polymer metal nanocomposites based on a miscible polymer blend

Bio-compatible actuators are required to exhibit a large actuation displacement and force at a low voltage for various applications in liquid environments, including swimming robots, biomedical catheters, biomimetic sensory-actuators, and drug delivery micro-pumps. Recently, ionic polymer metal nanocomposites (IPMNCs) based on Nafion have been widely used for bio-compatible actuators; however, they have been demonstrated to operate only at high voltages in the range of 2 to 5 V, resulting in water hydrolysis problems which are accompanied by a degradation of actuation performance. Here, we show that IPMNC actuators based on a poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)]/polyvinylpyrrolidone (PVP)/polystyrene sulfonic acid (PSSA) polymer blend membrane can exhibit a large actuation displacement and force at a low voltage of 1 V. Due to the ferroelectric nature of P(VDF-TrFE), the large dipole moment of P(VDF-TrFE) can cause strong intermolecular bonding, causing the P(VDF-TrFE)/PVP/PSSA blend membrane to be miscible. We found that the P(VDF-TrFE)/PVP/PSSA blend membrane with a blending ratio of 30/15/55 can produce the highest proton conductivity (0.0065 S cm−1) and ion exchange capacity (2.95 meq g−1) as compared to those of the commercial Nafion membrane, due to its miscible nature. Our IPMNC exhibits both an enhanced actuation displacement and force by up to 2 times in comparison with those of the IPMNC based on the commercial Nafion-based ionic membrane. Our P(VDF-TrFE)/PVP/PSSA IPMNC shows a stable actuation performance for up to 2200 cycles in hydrated conditions.

Enhanced sensing performance of carboxyl graphene–ionic liquid attached ionic polymer–metal nanocomposite based polymer strain sensors

Soft bendable polymer sensors have been widely used to monitor prosthetics, heartbeat, joint pain, and several other medical conditions because of their flexible nature. Recently, sensors based on piezoelectric inorganic materials, conducting polymers, and commercial Nafion based ionic polymer–metal nanocomposites (IPMNCs), have been extensively studied for sensor applications; however, existing inorganic and polymer materials exhibit low sensing currents due to weak interfacial bonding between the electrode and sensing material. Here, we show that biocompatible IPMNC sensors based on a carboxyl graphene (COG)–acidic ionic liquid (IL) (1-butyl-3-methylimidazolium-hydrogen sulfate)–poly(vinylidene fluoride–trifluoroethylene–chlorotrifluoroethylene) [P(VDF–TrFE–CTFE)]–polyvinylpyrrolidone (PVP)–polystyrene sulfonic acid (PSSA) ionic blend membrane can generate a high sensing current (6 mA cm−2) with a bending strain of 0.009. The ionic exchange capacity (IEC) (1.36 times), proton conductivity (3.4 times), and Youngs modulus (176 times) of P(VDF–TrFE–CTFE)/PVP/PSSA/COG ionic blend membranes are enhanced compared to those of P(VDF–TrFE–CTFE)/PVP/PSSA. In comparison to a commercial Nafion membrane, enhanced values of water uptake (WUP) (5.61 times), IEC (3.26 times), and Youngs modulus (6 times) were achieved by our P(VDF–TrFE–CTFE)/PVP/PSSA/COG/IL ionic blend membrane. Polymer sensors based on (PVDF–TrFE–CTFE)/PVP/PSSA/COG/IL IPMNC exhibit stable sensing currents in dry conditions for up to 6000 cycles. Our proposed blend fabricated through attaching COG and IL will find applications in several other devices such as supercapacitors due to its high capacitance (3.92 mF).

Comparative Analysis of MEMS Piezoelectric Materials for the Design of a Piezotube-Type Pressure Sensor

MEMS-based pressure sensors with high voltage sensitivity can be used in many areas of MEMS, biomedical, optical displays, automobile, etc. This paper focuses on the comparison of various types of MEMS piezoelectric materials which sense and convert the mechanical energy into electrical energy using MEMS technology. The model designing and working principle of proposed MEMS Piezotube-type pressure sensor is elucidated here. The modeling and simulation of MEMS Piezotube pressure sensor is done using COMSOL 5.2. The displacement of piezoelectric material and induced electric potential analysis are carried out for various types of MEMS piezoceramic materials. This paper shows the study of voltage generation using direct piezoelectric effect. Here, analysis is done in centimeter range making two sets of boundary conditions where internal fluid pressure of various ranges is applied onto MEMS Piezotube-type pressure sensor using various piezoceramic materials. Furthermore, analyses are done with increased value of pressure, but now the pressure is applied externally. The new result shows that there is a huge increment in induced electric potential on increasing the pressure and dimensions. Indirect piezoelectric effect is also shown in this paper, where on applying the electric field, material becomes strained and strain is directly proportional to electric field.