Moiré-free fingerprint sensors based on multilayer oxide-metal-oxide electrodes

Cho, Eun−Hyoung; Kim, Hyun Joon; Koo, Bon Won; Hong, Seog Woo; Jung, Won Seok; Kim, Haesung; Kim, Hong Suk; Chung, Soonwan; Kim, Yong‐Sung; Lee, Byung-Kyu; Lee, Chang Seung

doi:10.1364/oe.26.024973

Cited by 2 publications

(4 citation statements)

References 23 publications

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“…A higher transmittance implies a lower contrast when the patterns overlap, and thus, a pattern having the same period would be less noticeable according to the CSF. Therefore, the Moiré pattern may not be visible when the transmittance of the electrode is very high, even if the electrode pattern is not rotated or the electrode pitch is not adjusted, as suggested in a previous report 5 . However, the contrast sensitivity significantly varies according to the luminance and viewing angle of the object along with other factors 35 .…”

Section: Characterization and Demonstration Of Fingerprint Sensorsmentioning

confidence: 82%

“…However, the most convenient and intuitive location of the fingerprint sensor is on the front face. Various types of sensors that can recognize fingerprints on display screens have been developed [1][2][3][4][5][6][7][8][9][10][11] . Typical examples include capacitive, optical, and ultrasonic fingerprint sensors.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of the on-screen fingerprint sensor, a repetitive pattern of the display overlaps with another repetitive pattern of the sensor. Consequently, a Moiré pattern is observed, which can significantly reduce the display image visibility 5 .…”

Section: Introductionmentioning

confidence: 99%

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On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

et al. 2020

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In this study, a mutual capacitive-type on-screen fingerprint sensor, which can recognize fingerprints on a display screen to provide smartphones with full-screen displays with a minimal bezel area, is fabricated. On-screen fingerprint sensors are fabricated using an indium tin oxide transparent conductor with a sheet resistance of ~10 Ω/sq. and a transmittance of ~94% (~86% with the substrate effect) in the visible wavelength range, and assembled onto a display panel. Even at this high transmittance, the electrodes can degrade the display quality when they are placed on the display. The interference between periodic display pixel arrays and sensor patterns can lead to the Moiré phenomenon. It is necessary to find an appropriate sensor pattern that minimizes the Moiré pattern, while maintaining the signal sensitivity. To search for appropriate patterns, a numerical calculation is carried out over wide ranges of pitches and rotation angles. The range is narrowed for an experimental evaluation, which is used to finally determine the sensor design. As the selected sensor pitches are too small to detect capacitance variations, three unit patterns are electrically connected to obtain a unit block generating a larger signal. By applying the selected sensor pattern and circuit driving by block, fingerprint sensing on a display is demonstrated with a prototype built on a commercial smartphone.

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Section: Characterization and Demonstration Of Fingerprint Sensorsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

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On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

et al. 2020

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“…However, the production efficiency for these methods is always low, increasing the cost of the regular metal mesh-based FTCE. Furthermore, the appearance of the regular metal mesh-based FTCE still suffers from the Moiré pattern phenomenon, which limits its application in optoelectronic devices . In contrast, RM-FTCE, which is formed by metal grids with random orientation, can be fabricated by ingenious nature-inspired methods, such as the self-cracking template method, − grain boundary lithography, electrospinning nanofiber template method, spider silk web template method, and leaf venation method. , Among these methods, a lot of approaches, such as the self-cracking template method and grain boundary lithography, have the potential to be compatible with the conventional roll-to-roll process, indicating a promising potential for low-cost and large-scale fabrication.…”

Section: Introductionmentioning

confidence: 99%

Cohesively Enhancing the Conductance, Mechanical Robustness, and Environmental Stability of Random Metallic Mesh Electrodes via Hot-Pressing-Induced In-Plane Configuration

Wang¹,

Jiao²,

Huang

et al. 2021

ACS Appl. Mater. Interfaces

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Flexible transparent conductive electrode (FTCE) is highly desirable due to the fast-growing flexible optoelectronic devices. Several promising FTCEs based on metal material have been developed to replace conventional indium tin oxide (ITO). The random metal mesh is considered to be one of the competitive candidates. However, obtaining feasible random metal mesh with low sheet resistance, high transparency, good mechanical durability, and strong environmental stability is still a great challenge. Here, a random metal mesh-based FTCE with an in-plane structure, achieved by a facile hot-pressing process, is demonstrated. The hot-pressing process enables the fabrication of highly conductive FTCE with improved mechanical robustness and environmental stability. The in-plane FTCE shows a low sheet resistance of 1.63 Ω• sq −1 with an 80.6% transmittance, low relative resistance increase (RRI) of 7.9% after 240 h 85 °C/85% RH test, and low RRI of 8.0% after 10 5 cycles of bending test. Besides, various applications of the in-plane FTCE were demonstrated, including the flexible heater, flexible touch screen, and flexible electroluminescence. We anticipate that these results will spark interest in in-plane random metal mesh electrodes and enable the application of random metal mesh in flexible optoelectronic devices.

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Moiré-free fingerprint sensors based on multilayer oxide-metal-oxide electrodes

Cited by 2 publications

References 23 publications

On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

Cohesively Enhancing the Conductance, Mechanical Robustness, and Environmental Stability of Random Metallic Mesh Electrodes via Hot-Pressing-Induced In-Plane Configuration

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