Smart Material Constructed Flexible and Stretchable Electronics for Knee Joint Health Monitoring and Improved Drug Delivery

This paper presents a flexible and stretchable electronic device with multi-functionality. This device contains the functional node array coated smart materials and can be packaged with biocompatible polydimethylsiloxane (PDMS) films as a smart patch. Two kinds of smart materials are utilized: piezoelectric lead zirconate titanate (PZT) film for sensing acoustic emission (AE) wave and thermally activated Poly(N-isopropylacrylamide) PNIPAM film for delivering drug. The functional node array is implemented on a thin flexible titanium sheet with serpentine network electrically connected. This design has two advantages: (1) the serpentine network allows the node array to stretch in an arbitrary planar direction; (2) while the patch is stretched, the normal force exerted by the node can enhance the AE detection head coupling to the sensing object as well as increase the contact force/area of PNIPAM film. The fabrication and experimental results of the designed serpentine network AE sensing module along with the temperature controlled drug release element are reported. The demonstration of the smart patch assembled with a knee band strap for monitoring the knee joint motion is also described.