Table 3.

A review of printed respiratory rate sensors.

Group	Position	Printing Method	Substrate	Active Material	Sensing Method	Sensitivity
Al-Halhouli et al. [184,255,256]	Chest, abdomen	Inkjet	PDMS	Silver nanoparticles	Resistive/strain	0.11 S −1
Yang et al. [259]	Facemask	Screen	PVDF NM	Silver nanowires	Capacitive/pressure	4.2 kPa−1
Cao et al. [260]	Facemask	Screen	PVDF NM	Silver nanoparticles	Triboelectric/pressure	0.065–0.385 kPa−1
Lu et al. [262]	Mouth	Inkjet	glossy photo-paper	Graphene	Impedance/temperature, humidity	N/A
Su et al. [261]	Facemask	Inkjet	PET	Gold nanoparticles	Resistive/humidity	N/A
Mohapatra el at. [263]	Nose	Inkjet	Polyimide	Silver nanoparticles	Resistive/moisture	N/A