Polymeric Sensors and Actuators

Chapter 6

Mechanical Sensors

Mechanical sensor technologies have been reviewed, inter alia, in a monograph (1). Comprehensive descriptions of the principles of sensors for mechanical quantities are available in the literature (2,3).

The basic principle of mechanical sensors relies on the mechanical deformation of a device which is translated into an electrical signal. The mechanical deformation can be measured in a number of ways, such as piezoelectricity, change in the electric resistance with the geometry, change in the electric capacity, and changes in the resonant frequency of vibrating systems.

6.1 Basic Principles

6.1.1 Bending Sensors

A mechanical sensor has been described that is manufactured from a polymer film. Its upper part is modified to be electrically conductive, but its lower part remains as an insulator. When a strain is applied to this film, the mechanical sensor distorts. The electrical resistance of the upper part changes. In this way, the strain can be measured.

The polymer used can be a poly(imide), a poly(phenylquinoxaline) or a poly(phenylene sulfide) (4). The film can be irradiated by an ion beam via a mask to form patterns of conductive lines, aligned with the direction in which the sensor will distort during use. The conductive lines can also be produced by reactive ionic etching or photoablation, using an excimer laser.

The variation in resistance ΔR depends solely on angle θ representative for the flection. The mechanical sensor is capable of withstanding ...