Development of a Transparent Pressure Display with 20 Times Higher Sensitivity
Real-time 3D display of fingerprints with new sensor material
Application prospects for biometric authentication wearable devices


Domestic researchers have developed a technology capable of detecting even minute changes in pressure. This technology is suitable for fields such as biometric authentication, wearable devices, and medical assistive devices, as it can determine not only the intensity and location of pressure but also the three-dimensional surface information of the object to which the pressure is applied.

The Electronics and Telecommunications Research Institute (ETRI) announced on the 13th that, together with a research team from Seoul National University (Professor Yongtaek Hong and Researcher Byungmoon Lee), they have developed an ultra-sensitive transparent pressure sensor using nanocomposite materials that is up to 20 times more sensitive than existing sensors. This research achievement was published online in 'Nature Communications' on the 31st of last month.

Conventional pressure sensors are made by creating a cross pattern with electrodes and incorporating a sensor material whose conductivity changes depending on the pressure at the contact points. This structure had limitations, such as low sensitivity making it difficult to detect minute pressure changes, and the requirement to additionally process pressure signal data to view relevant information.

ETRI has developed a new sensor that utilizes nanomaterials and applies them to a stacked structure of quantum dot light-emitting devices, enabling enhanced sensitivity while allowing for direct visualization of pressure distribution. It is designed so that only the areas in contact with pressure emit light.

The research team used a composite material mixing conductive polymer nanowires and nanocellulose as a sensor material. They utilized the property that conductivity increases as the contact between nanowires increases.

To increase contact volume, it was made of a composite material into an ultra-thin, transparent, high-sensitivity sensor with a thickness of 1 µm (micrometer), which is 1/100 the thickness of a human hair. Approximately 100 layers can be stacked on the 1 µm sensor layer.

In addition, a quantum dot device with a sensor material was also created. The researchers placed a nanomaterial they developed on top of a quantum dot layer that emits light when electricity is applied, so that current flows and light is emitted only when pressure is applied.

The sensor developed by the research team is transparent, 2㎛ thick, and 100×100mm in size; when pressure is applied, the pressure distribution area is displayed in red in real time. RGB display is also possible.

The sensor sensitivity is sufficient to display a human pulse, and the pressure range is sufficient to indicate pressure when the entire palm is pressed. It can even detect needle-level pressure.

Since there is no need for a complex arrangement of electrodes, highly sensitive devices can be fabricated even with a thickness of 1㎛. Because the nanocomposite material is transparent, the device can also be made transparent, making it easy to mount and utilize on various substrates.

The sensor material is flexible and easy to apply via solution processing, making it advantageous for fabricating large-area substrates or wearable devices. Since the material is inexpensive and eco-friendly, it is harmless to the body, and results have been confirmed that its performance remains stable even when used for a long period in environments where everyday contamination, such as moisture, occurs.

By utilizing the ultra-high sensitivity performance of the sensor developed by the research team, it is possible to distinguish the load of an object and the appearance of its surface. The research team displayed the surfaces of objects with small, detailed patterns, such as the vein patterns of leaves, the shape and depth of fingerprints, in real time and rendered them in 3D through data processing.

Looking ahead, the research team anticipates that if the sensor is made into a thin film and attached directly to the skin, it will emit light in sync with the pulse, enabling the transmission of bodily data within hospitals. It is also expected to be useful for biometric security, as it can even represent the elevation of fingerprint ridges. Furthermore, when attached to a robot, the sensor can detect the roughness and smoothness of the objects it perceives.

The research team plans to transfer the technology to pressure sensor developers and related industries in sectors such as security, electronics, and medical fields while conducting further research to verify the stability of the sensors and their characteristics.