Ultraflexible Organic Active Matrix Sensor Sheet for Tactile and Biosignal Monitoring

Flexible sensors are currently the subject of intensive research, as they allow cost-effective and environmentally friendly production of large-area, flexible, and when fabricated on ultrathin substrates, highly conformable devices. Among many intriguing applications, tactile and biosignal monitoring, where lightweight sensors with high wearing comfort are particularly interesting, is focused on here. The required spatiotemporal resolution of the signals is achieved by integrating the sensors in an active matrix configuration. Organic ferroelectric transducers of high uniformity, characterized, for example, by a sensitivity spread of only 1.5%, are combined with similarly uniform ultralow noise level organic thin film transistors operating below 5 V, showing, for example, a threshold voltage variation of just 0.13 V, in a 12 × 12 sensor array. The transistors transition frequency of up to 160 kHz (saturation range) and 17 kHz (linear range) allows for a high spatiotemporal resolution of ≈3 mm at a frame rate of 1400 fps. The thickness of only 2.8 µm renders the organic active matrix sensor sheet ultraflexible and therefore virtually imperceptible on the human skin. Real-time monitoring of tactile modes in a subset of 8 × 3 pixels and of the pulse wave including heart rate and blood pressure using four sensors of the matrix is demonstrated.