Bio-mimetic synthetic cell hydrogel magnetometer

We present a bio-inspired hydrogel magnetometer where the cell potential (V _oc) between two hydrogels is used to measure an external magnetic field. Ferromagnetic particles located in the hydrogels move in response to the external field and change the V _oc (sensitivity ~ 3.7 V T^-1). As the field becomes larger than a critical field B _c (~38 mT), these particles puncture the hydrogel boundary shorting out the concentration gradient region and abruptly reducing the V _oc (sensitivity ~ 23.5 V T^-1). In this regime, the V _oc behaves similar to the neuron firing. In subsequent measurement cycles, the particles remain in punctured holes and the sensor behaviour is neuron-like with lower sensitivity (~20 V T^-1). V _oc also changes as a function of pressure (8 mV kPa^-1) and temperature (2 mV K^-1). After 4 h, the ionic concentration gradient diminishes in the device, and similar to biological cell fatigue, V _oc decreases and can be recharged with many different techniques.