Micromachined Piezoelectric Film-Based Flexible Electronics with Integration of Film-Self Temperature-Detecting Breath Sensor and Acetone Gas Sensor

The state-of-the-art wearable micromachined flexible electronics consisting of the breath sensor with self-temperature monitoring and acetone gas sensor are presented (Fig. 1). The breath sensor constructed by a freestanding patterned titanium film coated with 1 μm-thick piezoelectric BaTiO
3
film possessing two novelties: (1) the stiffness designable triangular cantilever with uniform stress distribution when utilizing its piezoelectric property for airflow sensing. (2) The fixed film region utilizing its negative temperature coefficient (NTC) thermistor effect as a temperature sensor. We believe this simple-structured breath sensor is reported for the first time worldwide. The film-based breath sensor is integrated with the charge amplifier circuit implemented on a polyimide film as wearing flexible electronic device. This device also integrated with the acetone gas sensor, possessing high sensitivity at room temperature, based on tin dioxide (SnO
2
) reduced graphene oxide (RGO) composite film.