This paper reports on the feasibility study of an ingestible pH sensor using polyaniline (PANI) of which conductivity depends on pH values. Ingestible pH sensors have the potential to promote gastrointestinal health. However, existing devices are still large due to the use of complex pH sensors and several button batteries, and thus have a risk to cause retention and obstruction. To address these issues, we propose a system that combines a PANI-based resistive pH sensor with an ultra-low power custom integrated circuit (IC) designed for ingestible sensors. The PANI-pH sensor can be simply fabricated by dropping a PANI solution solved in N-Methyl-2-Pyrrolidone solution on an interdigital electrode and exhibited approximately 1.8 times/pH as the resistance change rate to pH up to pH 9. Next, we built an experiment system using an evaluation board containing all the functions of the ingestible sensor, and demonstrated whole operation i.e. the pH measurement, making data packet, wireless transmission etc... Finally, our proposing system was proved to have little power consumption enough to operate for 5 days with a measurement frequency of once every 6 seconds even using a single silver oxide button battery. This research represents a significant step toward the realization of a small, affordable, and safe ingestible pH sensor.

This paper addresses a new insight into the properties of a tactile sensing microfinger. The tactile sensing microfinger integrates a pneumatic balloon actuator (PBA) and a liquid metal strain sensor. Integration of the actuator and sensor enables active sensing that is a sensor can approach and contact objects. This paper investigated the parameters that affect both actuator and sensor properties for the optimization of the microfinger design. It is possible to optimize the performance of actuator and sensor by controlling parameters such as bending stiffness EI. The design focuses on bending stiffness EI successfully improved the sensitivity of the liquid metal strain sensor.