Haptic touch sensor powered by static electricity
As the IoT evolves, tiny, low-power sensors and devices that can receive and send signals anytime and anywhere will become the norm. However, powering such a sensor or device is problematic due to size, weight and charging constraints off batteries. Also, changing batteries in countless devices raises a logistical nightmare. Researchers have proposed the triboelectric generator as a solution to the problem if they can be downsized for wearable electronics such as haptic sensors. The triboelectric generator provides energy in a semi-permanent manner by inducing triboelectricity from contact between different materials, just as how static electricity is produced in everyday life.
The Korea Institute of Science and Technology (KIST) has announced that a team of researchers led by Dr. Seoung-Ki Lee at the Center for Functional Composite Material Research have developed a haptic touch sensor that enhances the triboelectrification efficiency by more than 40% by forming crumple structured molybdenum disulfide through a joint study with Chang-Kyu Jeong, Professor of Advanced Materials Engineering at JeonBuk National University.
Today, general triboelectric generators excessively large and heavy at the required power levels for wearable electronic devices. Studies are being carried out that involve applying a two-dimensional semiconductor material that is atomically thin as an active layer in generating triboelectricity.
The intensity of the triboelectricity generated varies according to the type of two materials coming in contact. When it came to the two-dimensional materials used in the past, the transfer of electric charges with the insulating material did not occur smoothly, thus substantially lowering the output of energy produced from triboelectricity.
The joint research team formed by KIST and Jeonbuk National University adjusted the properties of molybdenum disulfide (MoS2), a two-dimensional semiconductor, and changed its structure to boost the triboelectricity generation efficiency. The material was crumpled during a strong heat treatment process that is applied in a semiconductor manufacturing process, and this resulted in a material with wrinkles to which internal stress has been applied. Due to the wrinkles, which help increase the contact area per unit area, the surface-crumpled MoS2 device can generate around 40% more power than a flat counterpart. Not only that, the triboelectricity output was maintained at steady levels in a cyclic experiment even after 10,000 repetitions.
By applying the crumpled two-dimensional material developed as above to a haptic touch sensor that can be used in a touchpad or touchscreen display, the joint research team came up with a lightweight and flexible self-powered touch sensor that can be operated without a battery. This type of haptic touch sensor with high power generation efficiency is sensitive to stimulation and can recognize touch signals even at a small level of force, without any electric power.
Dr. Seoung-Ki Lee from KIST said, “Controlling the internal stress of the semiconductor material is a useful technique in the semiconductor industry, but this was the first time that a material synthesis technique involving synthesis of a two-dimensional semiconductor material and application of internal stress at the same time was implemented” “It presents a way to increase the triboelectricity generation efficiency by combining the material with a polymer, and it will serve as a catalyst for the development of next-generation functional materials based on two-dimensional substances.”
This study was carried out with a grant from the Ministry of Science and ICT (MSIT), as part of the Institutional R&D Program of KIST and the Up-and-Coming Researcher Support Program.
Paper: https://dx.doi.org/10.1016/j.nanoen.2020.105266
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