Heat generation in active/passive layer-based piezoelectric actuators is unavoidable due to the mechanical, dielectric, and resistive losses in the material. In this work, a polyvinylidene fluoride (PVDF)-based unimorph cantilever actuator is developed with simulation and experimental studies on the effect of DC high voltages on heat production in the PVDF layer. A layer of one-way shape memory polymers (1W-SMPs) is integrated in the actuator to exploit the heat produced to increase the bending angle. The length and mounting location of the SMP layer impacts the bending of the actuator; by using an SMP layer with a length equal to half of the PVDF layer at the center of the unimorph actuator, the absolute bending angle is increased to 40° compared to the base piezo bending angle of 4° at 20 V/µm.

Stainless steel (SS304) is a widely used material in underwater nuclear applications due to its superior corrosion resistance and high strength. Along with these superior properties, the application demands neutron absorption and high wear resistance under dynamic operations. The ceramic reinforcements help to enhance these properties of metal alloy with a suitable composite design. The present work deals with the development of high wear-resistant and radiation (nuclear) tolerant boron carbide (B4C)–SS 304 composite material. SS304 metal matrix with 0–5 vol% of B4C ceramic reinforcement is produced by powder metallurgy technique. The presence of reinforcement was confirmed with X-ray diffraction analysis. Properties such as density, hardness, and water absorption are measured. A pin-on-disc tribology study is conducted to evaluate the coefficient of friction and wear of developed compositions at a sliding distance of 200 m, contact load of 10 N, and sliding speed of 1 and 5 m/s under dry lubrication conditions. The lowest density of 2.96 g/cc was noted for 15% B4C-reinforced composite as compared to the density of SS304 metal matrix (5.71 g/cc). The water absorption capacity of the composite was increased with percentage reinforcement, and it was found 62% higher than the unreinforced matrix. The hardness of composite increases with B4C particle reinforcement and maximum microhardness of 153 HV was measured for 15 vol% reinforced composites. Wear and coefficient of friction decrease with an increase in the percentage of B4C particles. At 15 vol% of B4C in the composite, lowest wear (1.91 mm3@1 m/s and 2.51 mm3@5 m/s) and COF (0.021@1 m/s and 0.042@5 m/s) were observed. This suggests that the developed composite can be effectively used in low-pressure–high-speed nuclear applications.

Polymers have enormous potential in the optoelectronic and biomedical fields due to flexibility, biocompatibility, and ease of fabrication. Recent developments in the use of terahertz (THz) waves for biomedical and security applications demand information on the optical properties of the polymers and polymer composites in this region. In the present work, transmission, refractive index (n), and extinction coefficient (k) of PVDF-TrFE (75/25 mol.) copolymer and PVDF-TrFE-CTFE (73/23/4 mol.) terpolymer films with different thicknesses (40 µm, 60 µm, 80 µm) are measured by the THz-TDS system (up to 1 THz). PVDF copolymer and terpolymer films show average transmission of more than 90% irrespective of thickness. The average refractive index of PVDF-TrFE (75/25 mol.) copolymer and PVDF-TrFE-CTFE (73/23/4 mol.) terpolymer films are 1.50±0.04 and 1.45±0.05 respectively. The estimated extinction coefficient is considerably low for both polymer films for frequencies less than 0.6 THz. The average indices for PVDF-TrFE and PVDF-TrFE-CTFE films are close, however, the loss in PVDF-TrFE films is larger than the PVDF-TrFE-CTFE films. High transmission, low loss and ferroelectric properties make these PVDF based polymers highly desirable in light-wave manipulation, flexible electronic and solar devices.

In the present study, a broad negative refractive index (NRI) performance is achieved in the terahertz frequency range (0.6-0.9 THz) through the design of multi-layered fishnet metamaterial (FMM). Herein, the conventional fishnet structure is modified by smoothing the sharp corners to reduce the electric field concentration and improve NRI. At corner radius, r = 30 µm, an effective refractive index of −11.14 is achieved with lower electric field concentration at the corners. A multilayer structure of up to 40 layers is studied to achieve a broad NRI frequency response. The frequency band of NRI response is improved from 0.034 THz for a single layer structure to 0.178 THz for 28 layer structure, almost 6 times the original bandwidth. With the increase in the number of layers, the improvement in NRI and Figure of Merit (FOM) is observed, and maximum NRI and FOM values of −87.5 and 12.67 are achieved at 28 layers. This multilayer broadband design can surpass tunable response of available electro-optic materials. With an optimal combination of NRI and FOM, the presented multilayer approach can achieve a low-loss, broadband performance.