Fig. 1. Design and characterization of a wireless device for monitoring the treatment of VLUs with compression stockings.

(A) Schematic, exploded-view illustration of an SCV with constituent layers and components: silicone elastomer, battery, BLE SoC, Wheatstone bridge circuits configured with a 3D pressure sensor (R_p) and a temperature sensor (R_T), and circuit traces (copper/PI). (B) Circuit and block diagrams of the system and its wireless interface to smartphones. Analog front-end circuits consist of two differential AMPs and Wheatstone bridge circuits including resistive sensors (R_P and R_T) and reference resistors (R, R_P0, and R_T0). A central processing unit (CPU) transmits the ADC-sampled data (pressure/temperature measurements; V_P and V_T) via BLE radio to user interfaces (smartphones). (C) Photographs of SCV on the leg of a healthy patient (left) and with compression stocking (right). (D) Photograph of SCV during bending and twisting. (E) Computed strains along the copper traces and the components on the flexible printed circuit board (FPCB) in twisted (left) and bent (right) configurations. Photo credit: Yoonseok Park, Northwestern University.