Silver Nanowires in Stretchable Resistive Strain Sensors

Silver nanowires (AgNWs), having excellent electrical conductivity, transparency, and flexibility in polymer composites, are reliable options for developing various sensors. As transparent conductive electrodes (TCEs), AgNWs are applied in optoelectronics, organic electronics, energy devices, and flexible electronics. In recent times, research groups across the globe have been concentrating on developing flexible and stretchable strain sensors with a specific focus on material combinations, fabrication methods, and performance characteristics. Such sensors are gaining attention in human motion monitoring, wearable electronics, advanced healthcare, human-machine interfaces, soft robotics, etc. AgNWs, as a conducting network, enhance the sensing characteristics of stretchable strain-sensing polymer composites. This review article presents the recent developments in resistive stretchable strain sensors with AgNWs as a single or additional filler material in substrates such as polydimethylsiloxane (PDMS), thermoplastic polyurethane (TPU), polyurethane (PU), and other substrates. The focus is on the material combinations, fabrication methods, working principles, specific applications, and performance metrics such as sensitivity, stretchability, durability, transparency, hysteresis, linearity, and additional features, including self-healing multifunctional capabilities.

A Simple Technique for the Precise Establishment of the Working Gap in an Electrochemical Discharge Machining Process and Some Experimental Results Thereof

The working gap (Wg) between a tooltip and a substrate surface is a critical process parameter affecting the quality metrics and precision of microstructures fabricated using an electrochemical discharge machining (ECDM) process. Despite the extensive investigation carried out on ECDM processes for the last several years, only a few researchers have explicitly explained the technique used to establish the Wg. In the present work, the authors propose a simple, cost-effective technique using a commercially available metallic feeler gauge and a multimeter to precisely establish a Wg in an ECDM process. A systematic experimental investigation was carried out using the proposed method to study the influence of Wg on the quality metrics such as the depth, width, edge linearity, heat-affected zone, and surface finish of fabricated microstructures on a glass substrate. Experimental results revealed that even a 2 µm difference in Wg significantly influenced the quality and quantity metrics of an ECDM process. It was observed that no machining occurred beyond a W_g of 25 µm even when a TTR as low as 0.5 mm/min and an applied voltage greater than 44 V were used. A micro-channel with improved quality metrics was obtained using a tool travel rate (TTR) of 1 mm/min with an applied voltage of 33 V and a Wg of 2 µm while using 30% NaOH as an electrolyte. The proposed method would be helpful for researchers to fabricate precise micro-channels on glass substrates using ECDM processes.