Smart Test Strips: Next-Generation Inkjet-Printed Wireless Comprehensive Liquid Sensing Platforms

By combining radio-frequency identification (RFID) and paper-microfluidics technologies, a low-cost first-of-its-kind platform for comprehensive liquid sensing, i.e., the smart test strip, is presented, which enables portable wireless real-time liquid sensing with handhold devices (e.g., cell phones), and integration of various multifunctional electrical and chemical sensors, for numerous Lab-on-Chip applications, including manufacturing control, environmental monitoring, and point-of-care medical diagnostics. The fabrication of RFID tags and two types of microfluidics are accomplished by a single inkjet-printing process in a cost-effective environmental-friendly additive manufacturing approach, which makes possible the production of disposable, lightweight, and flexible sensing platforms. Taking advantage of the proposed smart test strips platforms, we demonstrate two proof-of-concept high-performance electrical sensors based on interdigitated electrode topologies: a resistivity-based sensor with a 1782 Omega/(Omega*m) sensitivity; nevertheless, the proposed permittivity-based sensor with a 15%/epsilon(r) sensitivity, but the proposed integrated wireless platform, can facilitate the integration of even more chemical and electrical sensors. In addition, two on-strip antenna prototypes have been designed, optimized, and tested to work at 2.4 GHz and 13.56 MHz, respectively. Furthermore, the wireless interrogation of a complete proof-of-concept smart test strip is presented, which shows an excellent sensing resolution of 1.33 Omega over the range of 0-1371 Omega.