Korean researchers develop transparent nanoforce touch sensor for future wearables

Created via a thin, flexible, and transparent hierarchical nanocomposite film

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) have developed a new high-performance and transparent nanoforce touch sensor that could be used in future wearables.

Created via a thin, flexible, and transparent hierarchical nanocomposite (HNC) film, the sensor apparently features all the necessary characters for an industrial-grade application, such as high sensitivity, transparency, bending insensitivity, and manufacturability.

Force touch sensors that recognise the location and pressure of external stimuli have received considerable attention for various applications, such as wearable devices, flexible displays, and humanoid robots.

However, despite huge amounts of research and development over many years to improve pressure sensitivity to realise industrial-grade sensing devices, it remains a challenge to apply force touch sensors in flexible applications.

The his is because sensing performance is subject to change and degraded by induced mechanical stress and deformation when the device is bent.

Nevertheless, to overcome these issues, the Korean research team focused on the development of non-air gap sensors to break away from the conventional technology where force touch sensors need to have air-gaps between electrodes for high sensitivity and flexibility.

The proposed non air-gap force touch sensor is based on a transparent nanocomposite insulator containing metal nanoparticles which can maximise the capacitance change in dielectrics according to the pressure, and a nanograting substrate which can increase transparency as well as sensitivity by concentrating pressure.

As a result, the team succeeded in fabricating a highly sensitive, transparent, flexible force touch sensor that is mechanically stable against repetitive pressure.

To test the sensor worked, the scientists placed the sensing electrodes on the same plane as the neutral plane, the force touch sensor can operate, even when bending to the radius of the ballpoint pen, without changes in performance levels.

To ensure the sensor could be used in the wearable space, the research team applied it to a pulse-monitoring capable healthcare wearable device and detected a real-time human pulse.

They also claimed that a seven-inch large-area sensor could eventually be integrated into a commercial smartphone.