MEMS technology yields smallest, high sensitivity force sensor

August 07, 2015 // By Graham Prophet
ALPS has developed the “HSFPAR Series” Force Sensor, for force sensing in input devices and posture control in industrial equipment and robots, using MEMS technology to achieve the smallest size.

Demand for high-precision pen-shaped input devices (stylus pens) is growing, Alps says, with the rising popularity of digital drawing and painting. Stylus pens, or styli, contain force sensors that are used to trace the trajectory of the pen tip, as well as to reproduce different thicknesses in the artwork corresponding to the pressure applied. To enable smoother tone transitions, however, styli require sensors with high resolution, leading to pen shafts that are too thick.

Similarly, demand for compact, highly sensitive force sensors for applications such as load detection on touch or contact, and load balance and grip strength control, is expected to rise.

Force sensors today (Alps notes) are generally either semiconductor strain gauge or metallic strain gauge types, and both have their issues. Semiconductor strain gauge force sensors offer high precision, but are large. Metallic strain gauge force sensors, on the other hand, can be made compact, though this comes with diminished sensitivity.

Responding to these issues, Alps Electric has developed a versatile, high-precision force sensor, the HSFPAR Series. The force sensor was developed by applying to a semiconductor strain gauge original MEMS and packaging technologies built up over the years. Not only does the HSFPAR Series have compact, low-profile dimensions of 2.00 × 1.60 × 0.66 mm, the sensor can detect stress as low as 0.01N, enabling high-precision sensing of, for example, minor variations in pen pressure and load shift in robots.

The HSFPAR Series is also available as a unit type with a FPC (Flexible Printed Circuit) included for easy integration into end products. It is suitable for diverse applications, including such input devices as styli and touch panels, as well as industrial equipment and robots.