A Highly Elastic, Capacitive Strain Gauge Based on Percolating Nanotube Networks

Cohen, Daniel; Mitra, Debkishore; Peterson, Kevin; Maharbiz, Michel M.

doi:10.1021/nl204052z

Cited by 457 publications

(357 citation statements)

References 30 publications

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“…[1][2][3][4] "Electronic skin" is generally taken to be a stretchable sheet with area above 10 cm 2 carrying sensors for various stimuli, including deformation, pressure, light and temperature. The sensors report signals through stretchable electrical conductors [5] (e.g., carbon grease, [6] microcraked metal films, [1] serpentine metal lines, [2] graphene sheets, [7] carbon nanotubes, [8][9][10] silver nanowires, [11] gold nanomeshes, [12] and liquid metals [13,14] ). These conductors transmit signals using electrons.…”

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confidence: 99%

Ionic skin

et al. 2014

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Our skin is a stretchable, large-area sheet of distributed sensors. These properties of skin have inspired the development of mimics, with differing levels of sophistication, to enable wearable or implantable electronics for entertainment and healthcare. [1][2][3][4] "Electronic skin" is generally taken to be a stretchable sheet with area above 10 cm 2 carrying sensors for various stimuli, including deformation, pressure, light and temperature. The sensors report signals through stretchable electrical conductors [5] (e.g., carbon grease, [6] microcraked metal films, [1] serpentine metal lines, [2] graphene sheets, [7] carbon nanotubes, [8][9][10] silver nanowires, [11] gold nanomeshes, [12] and liquid metals [13,14] ). These conductors transmit signals using electrons.They meet the essential requirements of conductivity and stretchability, but struggle to meet additional requirements in specific applications, such as biocompatibility in biometric sensors, [15] and transparency in tunable optics. [16,17] By contrast, sensors in our skin report signals using ions. Here we explore the potential of ionic conductors in the development of a new type of sensory sheet, which we call "ionic skin".The sensory sheet is highly stretchable, transparent, and biocompatible. It readily monitors large deformation, such as that generated by the bending of a finger. It detects stimuli with wide dynamic range (strains from 1% to 500%). It measures pressure as low as 1 kPa, with small drift over many cycles. A sheet of distributed sensors covering a large area can report the location and pressure of touch. High transparency allows the sensory sheet to transmit electrical signals without impeding optical signals.Many ionic conductors, such as hydrogels and ionogels, are highly stretchable and transparent. [18][19][20] These gels are polymeric networks swollen with water or ionic liquids. They behave like elastic solids and eliminate the need for containers as required in the case of liquid metal conductors. Whereas familiar elastic gels, such as Jell-O, are brittle and easily rupture, the recent decade has seen the development of hydrogels and ionogels as tough as elastomers. [20][21][22] Many hydrogels are biocompatible. They can be made softer than tissues, achieving the "mechanical invisibility" required for biometric sensors, which monitor soft tissues without 3 constraining them. Although most hydrogels dry out in open air, hydrogels containing humectants retain water in environment of low humidity, and ionogels are nonvolatile in vacuum. [18][19][20] We have recently used ionic conductors-together with stretchable and transparent dielectrics-to make actuators, which deform in response to high voltages, on the order of kilovolts. [18] By contrast, the sensors described here deform in response to applied forces, giving signals that can be measured using voltages below 1 volt. To illustrate principles in our design of the ionic skin, consider a simple example-a dielectric sandwiched between two ionic conductors (Figure 1). In many...

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confidence: 99%

Ionic skin

et al. 2014

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“…The key toward stretchable sensing is to develop highly stretchable, conductive materials as electrodes. So far, conductive fabric,85, 86 nanocomposites,87 conductive polymer/hydrogel,57 bulking thin film,88 and conductive liquid89 have been deployed as stretchable electrodes. Capacitive sensors have good linearity, high sensitivity, large dynamic range, and rapid response.…”

Section: Sensing Technologies For Soft Robotsmentioning

confidence: 99%

Toward Perceptive Soft Robots: Progress and Challenges

2018

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In the past few years, soft robotics has rapidly become an emerging research topic, opening new possibilities for addressing real‐world tasks. Perception can enable robots to effectively explore the unknown world, and interact safely with humans and the environment. Among all extero‐ and proprioception modalities, the detection of mechanical cues is vital, as with living beings. A variety of soft sensing technologies are available today, but there is still a gap to effectively utilize them in soft robots for practical applications. Here, the developments in soft robots with mechanical sensing are summarized to provide a comprehensive understanding of the state of the art in this field. Promising sensing technologies for mechanically perceptive soft robots are described, categorized, and their pros and cons are discussed. Strategies for designing soft sensors and criteria to evaluate their performance are outlined from the perspective of soft robotic applications. Challenges and trends in developing multimodal sensors, stretchable conductive materials and electronic interfaces, modeling techniques, and data interpretation for soft robotic sensing are highlighted. The knowledge gap and promising solutions toward perceptive soft robots are discussed and analyzed to provide a perspective in this field.

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“…[107] When the applied strain is released, it is difficult for the nanomaterials to slide back to the initial position or for the cracks to be completely closed. Due to the viscoelasticity of polymers and the friction between the nanomaterials and the polymer matrix during loading and unloading, rearrangement of nanomaterials Polyaniline doped AuNW/Latex rubber [68] Resistive 2-12 for 0-100% 149.6% -Human finger-controlled robotic arm system AuNW/Latex rubber [44] Resistive 9.9 (0-5%), 6.9 (5-50%) 300% 0.01% Data glove, monitoring of forearm muscle movement, cheek movement, phonation, and wrist pulse AgNW/Ecoflex/AgNW [41] Capacitive 0.7 50% -Monitoring of finger bending and knee motion CNT/Ecoflex/CNT [25] Capacitive 0.4 50% --CNT/silicone/CNT [127] Capacitive 0.99 100% -Robotic linkage CNT/Dragon Skin/CNT [129] Capacitive 1 300% -Date glove, monitoring of balloon inflation and chest movement PVDF-TrFE with graphene FET [134] Piezoelectric 389 ≈0.3% 0.008% Monitoring of hand movement ZnO NW array [132] Piezoelectric 1813 0.8% --Carbon fiber-ZnO NW [217] Piezoelectric 60-80 1.2% 0.2% -www.advancedsciencenews.com www.advhealthmat. de and opening of cracks results in time delay between electrical output and mechanical input.…”

Section: Resistive Strain Sensorsmentioning

confidence: 99%

“…The reported GF varies between 0.4 and 1.3 due to the fringing fields associated with finite-size parallel-plate capacitors, [127] and the strain range varies between 50% and 300% depending on the stretchability of the electrodes and the dielectric. [24,25,41,43,[127][128][129][130][131] For example, a capacitive strain sensor was fabricated with stretchable AgNW/PDMS conductors as the top and bottom electrodes and Ecoflex as the dielectric material. The sensor exhibited good linearity, GF of 0.7 and a sensing range of 50%.…”

Section: Capacitive Strain Sensorsmentioning

confidence: 99%

Nanomaterial‐Enabled Wearable Sensors for Healthcare

Yao

Swetha

Zhu

2017

Adv Healthcare Materials

435

296

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humidity level, and concentration of harmful gases, and airborne particulates can provide valuable information for the prediction, management, and treatment of chronic diseases. [4,5] In addition to the applications in wearable health monitoring, continuous tracking of daily and sports activities can offer an efficient way to assess the well-being and athletic performances. [6] In order to ensure a robust and conformal contact with the curvilinear, coarse, and dynamic surface of skin without impeding daily activities, the wearable sensor should have low modulus and high stretchability. The epidermis has a modulus of 140-600 kPa while the dermis has an even lower modulus of 2-80 kPa. [7] Skin itself can be stretched elastically up to 15% and with the help of wrinkles and creases, the overall stretchability can reach as high as 100% during daily motions. [8] In addition to good wearability, wearable sensors should be highly sensitive, lightweight, low-cost, and with low power consumption. To achieve these features, nanomaterials that are compliant, possessing larger surface area and exceptional material properties, and compatible with low-cost fabrication processes are widely employed as building blocks for developing wearable sensors.In this review, we start from a brief overview of nanomaterials, their related structural designs and fabrication processes (Section 2). Following that, recent advances of nanomaterialenabled wearable sensors including temperature, electrophysiological, strain, tactile, electrochemical, and other sensors will be summarized (Section 3). A survey on the integration of multiple sensors and other components into wearable systems will be given in Section 4. The application of nanomaterialenabled wearable sensors for healthcare including health monitoring, activity tracking, and electronic skin will be presented in Section 5. The challenges and opportunities will be discussed at the end. Nanomaterials, Structural Designs, and Fabrication ProcessesNanomaterials can be classified into two categories-top-down fabricated ones and bottom-up synthesized ones. [9] The focus of this review is on the wearable sensors based on bottom-up synthesized nanomaterials. Nanomaterials can be synthesized into various dimensions, from 0D such as metallic nanoparticles (NPs), to 1D such as carbon nanotubes (CNTs), and metallic nanowires (NWs), to 2D such as graphene and transition metal Highly sensitive wearable sensors that can be conformably attached to human skin or integrated with textiles to monitor the physiological parameters of human body or the surrounding environment have garnered tremendous interest. Owing to the large surface area and outstanding material properties, nanomaterials are promising building blocks for wearable sensors. Recent advances in the nanomaterial-enabled wearable sensors including temperature, electrophysiological, strain, tactile, electrochemical, and environmental sensors are presented in this review. Integration of multiple sensors for multimodal sensing and integration with...

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A Highly Elastic, Capacitive Strain Gauge Based on Percolating Nanotube Networks

Cited by 457 publications

References 30 publications

Ionic skin

Ionic skin

Toward Perceptive Soft Robots: Progress and Challenges

Nanomaterial‐Enabled Wearable Sensors for Healthcare

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