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Sensors (Basel). 2015 Nov 13;15(11):28732-41. doi: 10.3390/s151128732.

Development of a Carbon Nanotube-Based Touchscreen Capable of Multi-Touch and Multi-Force Sensing.

Author information

1
Next Generation Convergence Sensor Research Center, Korea Electronics Technology Institute, 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Korea. kimwh@keti.re.kr.
2
Display and Nanosystem Laboratory, Department of Electrical Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea. kimwh@keti.re.kr.
3
Next Generation Convergence Sensor Research Center, Korea Electronics Technology Institute, 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Korea. ajounasa@gmail.com.
4
Next Generation Convergence Sensor Research Center, Korea Electronics Technology Institute, 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Korea. yhkwak@keti.re.kr.
5
Next Generation Convergence Sensor Research Center, Korea Electronics Technology Institute, 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Korea. parkkb@keti.re.kr.
6
Display and Nanosystem Laboratory, Department of Electrical Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea. bkju@korea.ac.kr.
7
Next Generation Convergence Sensor Research Center, Korea Electronics Technology Institute, 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Korea. kimkn@keti.re.kr.

Abstract

A force sensing touchscreen, which detects touch point and touch force simultaneously by sensing a change in electric capacitance, was designed and fabricated. It was made with single-walled carbon nanotubes (SWCNTs) which have better mechanical and chemical characteristics than the indium-tin-oxide transparent electrodes used in most contemporary touchscreen devices. The SWCNTs, with a transmittance of about 85% and electric conductivity of 400 Ω per square; were coated and patterned on glass and polyethyleneterephthalate (PET) film substrates. The constructed force sensing touchscreen has a total size and thickness of 62 mm × 100 mm × 1.4 mm, and is composed of 11 driving line and 19 receiving line channels. The gap between the channels was designed to be 20 µm, taking visibility into consideration, and patterned by a photolithography and plasma etching processes. The mutual capacitance formed by the upper and lower transparent electrodes was initially about 2.8 pF and, on applying a 500 gf force with a 3 mm diameter tip, it showed a 25% capacitance variation. Furthermore, the touchscreen can detect multiple touches and forces simultaneously and is unaffected by touch material characteristics, such as conductance or non-conductance.

KEYWORDS:

multi-force; multi-touch; single-walled carbon nanotubes (SWCNTs); touchscreen

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