Flex sensor

A flex sensor or bend sensor is a sensor that measures the amount of deflection or bending. Usually, the sensor is stuck to the surface, and resistance of sensor element is varied by bending the surface. Since the resistance is directly proportional to the amount of bend it is used as goniometer, and often called flexible potentiometer.
Applications.
Flex sensor is used in wide areas of research from computer interfaces, rehabilitation, security systems and even music interfaces. It is also famous among students and Hobbyists.
Human Machine Interface devices.
Dataglove is common HMI device, that is made possible by flex sensors. The sensing element of deflections of dataglove is flex sensor.
Rehabilitation Research.
In Rehabilitation research, wired gloves or dataglove is used to record the joint movement.
Security Systems.
Movement of doors is monitored by placing the sensor at the hinge. Also, damage to metal structures can be identified using the sensor.