Microfabricated impedance sensors for concurrent tactile, biopotential, and wetness detection

Several biomedical applications require concurrent measurement of movement of the subject, sensing of the biopotentials and detection of wetness caused by bodily fluids. This paper presents the use of flexible capacitive tactile sensing arrays for concurrent monitoring of biopotential and wetness. This has been enabled by designing the cross-section of the capacitive sensor in a specific “H” shape where the movement of the capacitive plates is used for estimating the presence and the value of tactile forces. The capacitive plates act as biopotential sensors when coupled to the skin and the presence of conductive fluids in-between the plates can be sensed through impedance spectroscopy. We have designed a preliminary miniaturized circuit front-end using commercial-of-the-shelf components to interface the sensors and wirelessly transmit the data through a Bluetooth low energy link. Using the designed circuitry, the force applied to the pixel in the array has been estimated through capacitive sensing with a linear change in the capacitance with the applied force. Same sensor was used to detect EKG waveforms and sense the presence of wetness and salinity using impedance characterization.