Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have produced a high-performance and transparent nanoforce touch sensor by developing a thin, flexible, and transparent hierarchical nanocomposite (HNC) film. The team said their sensor features all the necessary characters for industrial-grade application: high sensitivity, transparency, bending insensitivity, and manufacturability.
Because of their ability to recognize the location and pressure of external stimuli, force touch sensors can play an important role in wearable devices, flexible displays, and humanoid robots. However, applying force touch sensors in flexible applications is a challenging process because sensing performance can change and degrade due to induced mechanical stress and deformation when the device is bent, reports ScienceDaily.
To overcome these obstacles, the researchers decided to develop sensors without any air gaps. The conventional technology uses touch sensors with air gaps between electrodes for high sensitivity and flexibility.
The non-air-gap force sensor has transparent nanocomposite insulator containing metal nanoparticles which can maximize the capacitance change in dielectrics according to the pressure, and a nanograting substrate which can increase transparency as well as sensitivity by concentrating pressure. That’s how the team was able to develop a highly sensitive, transparent, flexible force touch sensor that is mechanically stable against repetitive pressure.
By placing the sensing electrodes on the same level as the neutral plane, the researchers enabled the force touch sensor to operate even when bending to the radius of the ballpoint pen, without changes in performance levels.
The newly proposed touch sensor also meets the requirement in mass production like large-area uniformity, production reproducibility, and reliability according to temperature and long-term use.
To test the sensor, the researchers applied it to a pulse-monitoring wearable device and detected a real-time human pulse. Additionally, the researchers confirmed with HiDeep, Inc. that a seven-inch large-area sensor can be integrated into a commercial smartphone.