Low‐Cost Paper‐Based Conducting Polymer‐Hydrogel Flexible Bio‐Radar Sensor for Detecting Biological Objects.

Bio‐machine interface (BMI) is a crucial bridge for information exchange between living organisms and smart electronics. Flexible bio‐radar sensors, an important component of BMI devices, can measure spatial information of biological objects in real time and thus have attracted considerable attention owing to their wide applicability. However, in various practical scenarios, developing noncontact‐type flexible bio‐radar sensors for remote identification and detection of free‐behaving biological objects remains a challenge. To address this, paper‐based conducting polymer‐hydrogel (PCPH) bio‐radar sensors can be fabricated using a simple, low‐cost process. An intertwined core/shell microstructure of a conducting polymer‐hydrogel compound is formed on the fibers of the paper substrate. The resulting PCPH sensors exhibit a highly sensitive and spatial‐dependent response to a human finger based on an inductance mechanism. Attributed to the merits of the fabricated PCPH bio‐radars, complex behaviors of a human finger and hand using a customized multilevel security protection system and multichannel virtual piano system, respectively, are successfully detected. Furthermore, the detection limit of the PCPH sensors is verified by performing unattended monitoring and automatic analysis of the feeding and defensive behaviors of freely moving mice. These results prove the advantages of flexible PCPH bio‐radar sensors and demonstrate their application potential in BMIs. [ABSTRACT FROM AUTHOR]