Materials-Enabled Stretchable, Flexible and Wearable Electronics and Their Biomedical Applications

The pursuit of state-of-the-art stretchable, flexible and wearable electronics has changed our daily-life activities. To achieve the desired stretchability designs that can stretch due to topology and intrinsically stretchable materials significantly impact the efficacy of IoT and IoE applications [1,2]. As the mechanics of these devices dictate the overall response of the devices, the geometrical topology of interconnects such as serpentine and lateral spiral play a decisive role. Likewise, various materials, including copper and carbon nanotubes, have proved their great performance for identical devices while encapsulating in flexible polymers. Therefore, these stretchable designs and materials play an important role in bio-related flexible devices. Currently, wearable and flexible electronics analyze sweat, glucose, blood pressure, and other skin conditions. However, localized jaw-bone swelling called parotid swelling caused by some viruses has never been tracked before. This work reports carbon nanotubes (CNTs)-based piezoresistive sensing patch encapsulated in a highly flexible polymer and can record muscle deformations in real-time. The developed patch offers an excellent gauge factor (~16) for in-plane stretching and spatial expansion with low hysteresis. We fabricated the pneumatic actuator that experienced volumetric expansion and thus redefined the gauge factor to calibrate the volumetric muscle expansion. Moreover, we employ a Bluetooth-low-energy system that can send information about muscle activity in real-time to a smartphone app. We utilized COMSOL calculations to reveal the mechanical robustness of the patch. The experiments showed the sensing patch's greater cyclability, making it a great choice for personal healthcare, i.e., monitoring the real-time POC of human muscle swelling. Likewise, another application of copper-based stretchable interconnect is in thermal therapy. Thermal therapy is widely used to treat arthritis- the stiffness or pain of human muscle/bone. This work reveals the copper-based stretchable thermal patch that can digitally control the temperature of the patch, making it an excellent device for thermal therapy. We have used a CMOS-compatible nano/microfabrication scheme to make the thermal patch encapsulated in polyimide, making it flexible. The developed thermal patch gives a safe range of heating, can be stretched to fit any part of the body, and be wirelessly controlled. Our results have shown the exciting applications of copper and CNT-based smart patches, opening doors to various futuristic bio-medical applications.<br/><b>References</b><br/>1- N. Qaiser, A. N. Damdam, S. M. Khan, S. Bunaiyan, M. M. Hussain, Adv. Funct. Mater. 2007445 (2020).<br/>2- N. Qaiser, A. N. Damdam, S. M. Khan, S. F. Shaikh, M. M. Hussain, Appl. Phys. Lett., 115, 181904 (2019).