Rough‐Surface‐Enabled Capacitive Pressure Sensors with 3D Touch Capability

Lee, Kilsoo; Lee, Jae Hong; Kim, Gwangmook; Kim, Young-Jae; Kang, Sanghyeok; Cho, Sungjun; Kim, Seul Gee; Kim, Jae Kang; Lee, Wooyoung; Kim, Dae Eun; Kang, Shinill; Lee, Taeyoon; Shim, Wooyoung

doi:10.1002/smll.201700368

Cited by 147 publications

(123 citation statements)

References 62 publications

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“…Various advanced materials have been used to fabricate the active layer, such as silver nanowires (AgNWs),[3h,9] copper nanowires (CuNWs), gold nanowires (AuNWs), carbon nanotubes (CNTs), graphene, and conductive polymers. [3c,14] In addition to the use of new materials, the properties of flexible sensors may be enhanced by constructing sensors with novel structures …”

Section: Introductionmentioning

confidence: 99%

High‐Performance Pressure Sensors Based on 3D Microstructure Fabricated by a Facile Transfer Technology

Liu

Huang

Zheng

et al. 2019

Adv Materials Technologies

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In this paper, a high‐performance pressure sensor that imitates the sensing functions of human skin is proposed. A rough poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film transferred from abrasive paper acts as the sensing layer, while silver nanowires deposited on the bottom Ecoflex film with a 3D microstructure serve as the electrodes. Because of the bionic hierarchical structure, the resulting sensor exhibits a high pressure sensitivity of 6.13 kPa−1, low limit of detection (20 Pa), low operating voltage (0.1 V), and broad sensing range (up to 90 kPa). Furthermore, as the sensor is ultrathin, ultraflexible, and stretchable, it can easily conform to the uneven surface of human skin to allow monitoring of physical signals from the human body or detect the tactile stimulation of objects. In addition, a sensor array consisting of 4 × 4 pixels is assembled to realize the precise mapping of spatial pressure distribution. By virtue of its superior performance and low‐cost fabrication, the proposed pressure sensor may potentially be applied to next‐generation wearable devices such as e‐skin, soft robotics, and human–machine interaction systems.

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Section: Introductionmentioning

confidence: 99%

High‐Performance Pressure Sensors Based on 3D Microstructure Fabricated by a Facile Transfer Technology

Liu

Huang

Zheng

et al. 2019

Adv Materials Technologies

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“…Paper electronics is thriving in electronic security, flexible display, and biological diagnose for its outstanding features such as low‐cost, lightweight, and disposability . A series of investigations were dedicated to create functional modules on paper like 3D antenna, sensor, actuator, memory, and transistor . Recently, by integrating many functional modules together through paper‐based circuits, more complex functional systems were realized, such as a keyboard, sensor system, and touch panel .…”

Section: Introductionmentioning

confidence: 99%

Recyclable Liquid Metal‐Based Circuit on Paper

Qin

Zhou

et al. 2018

Adv Materials Technologies

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and touch panel. [18] As people expected, [17] the processability, performance, and stability of electronic materials are basic characteristics of paper electronics which demand that paper-based circuits must have controllable scale, low resistance and high stability under deformation. Although most paper electronics are disposable, the circuits on paper will also raise environmental concern as they cannot be degraded or recycled like their substrate paper. [19] Burning is the popular method to recycle functional materials such as silver nanoparticles on paper, [1,20,21] it will be detrimental to environment and functional materials which are also difficult to be separated from the debris of paper. Therefore, an environmentally friendly method for fabricating and recycling of paper-based circuits is urgently needed. Basically, all paper electronic devices contain functional modules and circuits. The circuit with controllable scale and high folding stability is the key point on deciding the integration level of devices and electrical stability under deformation. Recently, the fabrication of flexible circuits on paper is mostly based on the connection of tiny conductors, such as metal nanoparticles, [3,7,9,18,22,23] metal nanowires, [15,24] and graphene. [16] Alternatively, conductive liquids (especially liquid metals) were expected to realize circuits with high folding stability for intrinsically combined characteristics of both high electrical conductivity and excellent fluidity. [25] Liquid metal (LM, Galinstan: 68.2 wt% Ga, 21.8 wt% In, 10 wt% Sn [26] ) exhibits favorable properties such as low melting point, [27] high electrical conductivity, [28] and low toxicity. [29] LM has been patterned on a variety of smooth substrates such as polydimethylsiloxane and polyvinyl chloride [25,26,[30][31][32][33][34][35][36][37] to function as circuits, sensors, and antennas. [25,31,32,[37][38][39] However, impeded by the porous topography of paper, it is hard to reduce the line-width of paper based LM circuits thinner than 200 µm with methods like direct writing, [40] desktop printing, [37,41] and screen printing. [42] With the LM, here the method for fabricating circuits with controllable line-width and high stability is demonstrated, and these circuits can be recycled based on the transforming mechanism between different morphologies of LM (bulk, wires, and microparticles). Bulk LM can be deformed into LM particles (LMPs) by sonication. [43] Then, LMPs can be deposited on paper which can further be selectively transformed into LM wires through mechanically sintering. [38,44] Two strategies were introduced in the mechanically sintering process to control the width of circuit (pristine circuit) by controlling the contact Paper electronics is considered very environmentally friendly, but effective recyclability of metallic circuits on paper still needs more improvement. Therefore, liquid metal (Galinstan) circuits based on the reversible conversion from particles to wires are fabricated on paper using mechanical methods, i....

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“…When a larger ionic liquid droplet with 600 µm diameter is used, a capacitance change from 1 to 250 pF is observed under a pressure of 8 kPa (Figure S4 in the Supporting Information). In this case, the sensitivity is calculated to be 31.1 kPa −1 , which is one of the highest values reported in the medium‐pressure range (> a few kPa) so far (see Table S1 in the Supporting Information) . Although higher sensitivities have been reported in the previous reports, these values are typically obtained in extremely low pressure regimes (below 1 kPa) .…”

Section: Resultsmentioning

confidence: 54%

“…It has been reported that the viscoelastic behavior of the elastomer in the capacitive‐type pressure sensor significantly increases the relaxation time under unloading . The short relaxation time in our sensor originates directly from the use of an ionic liquid with viscosity lower than that of a sticky elastomer, such as poly(dimethylsiloxane) (PDMS) or ecoflex . When a larger ionic liquid droplet with 600 µm diameter is used, a capacitance change from 1 to 250 pF is observed under a pressure of 8 kPa (Figure S4 in the Supporting Information).…”

Section: Resultsmentioning

confidence: 88%

Enhanced Sensitivity of Iontronic Graphene Tactile Sensors Facilitated by Spreading of Ionic Liquid Pinned on Graphene Grid

Kim

Lee

Hwang

et al. 2020

Adv Funct Materials

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Iontronic graphene tactile sensors (i‐GTS) composed of a top floating graphene electrode and an ionic liquid droplet pinned on a bottom graphene grid, which can dramatically enhance the performance of capacitive‐type tactile sensors, are presented. When mechanical stress is applied to the top floating electrode, the i‐GTS operates in one of the following three regimes: air–air, air–electric double layer (EDL) transition, or EDL–EDL. Once the top electrode contacts the ionic liquid in the i‐GTS, the spreading behavior of the ionic liquid causes a capacitance transition (from a few pF to over hundreds of pF). This is because EDLs are formed at the interfaces between the electrodes and the ionic liquid. In this case, the pressure sensitivity increases to ≈31.1 kPa−1 with a gentle touch. Under prolonged application of pressure, the capacitance increases gradually, mainly due to the contact line expansion of the ionic liquid bridge pinned on the graphene grid. The sensors exhibit outstanding properties (response and relaxation times below 80 ms, and stability over 300 cycles) while demonstrating ultimate signal‐to‐noise ratios in the array tests. The contact‐induced spreading behavior of the ionic liquid is the key for boosting the sensor performance.

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Rough‐Surface‐Enabled Capacitive Pressure Sensors with 3D Touch Capability

Cited by 147 publications

References 62 publications

High‐Performance Pressure Sensors Based on 3D Microstructure Fabricated by a Facile Transfer Technology

High‐Performance Pressure Sensors Based on 3D Microstructure Fabricated by a Facile Transfer Technology

Recyclable Liquid Metal‐Based Circuit on Paper

Enhanced Sensitivity of Iontronic Graphene Tactile Sensors Facilitated by Spreading of Ionic Liquid Pinned on Graphene Grid

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