Polyurethane foam coated with a multi-walled carbon nanotube/polyaniline nanocomposite for a skin-like stretchable array of multi-functional sensors

Abstract

Body-attachable sensors can be applied to electronic skin (e-skin) as well as safety forewarning and health monitoring systems. However, achieving facile fabrication of high-performance, cost-effective sensors with mechanical stability in response to deformation due to body movement is challenging. Herein we report the material design, fabrication and characteristics of a skin-like stretchable array of multi-functional (MF) sensors based on a single sensing material of polyurethane foam coated with multi-walled carbon nanotube/polyaniline nanocomposite, which enables simultaneous detection of body temperature, wrist pulse and ammonia gas. These sensors exhibit high sensitivity, fast response and excellent durability. Furthermore, the fabricated sensor array shows stable performance under biaxial stretching up to 50% and attachment to skin owing to the use of directprinted Galinstan liquid metal interconnections. This work proposes a facile method for fabrication of high-performance, stretchable MF sensors via appropriate selection of sensor design and functional materials that are applicable to e-skin and health monitoring systems. NPG Asia Materials (2017) 9, e448; doi:10.1038/am.2017.194; published online 17 November 2017 INTRODUCTIONWearable electronics have attracted considerable attention for use in electronic skin (e-skin) and health monitoring systems in order for a comfortable and secure life. 1-5 e-Skin is a human interactive device that can simultaneously sense signals from the body and respond to the environment. Thus it should be capable of measuring the five types of senses (taste, sight, hearing, olfactory and touch sensation) with high sensitivity and show mechanical stability against deformation due to skin movement. As a result, e-skin is required to be very thin and have a strain-relaxed design. 6 Because of the increasing importance of e-skin, extensive efforts have been undertaken to develop various sensors with high sensitivity. 7 Beyond the conventional sensor that can detect a single stimulus, novel advanced sensors for simultaneous monitoring of multiple stimuli (multi-functional (MF) sensors) have been actively investigated. 8,9 For practical application of such MF sensors, it is necessary to eliminate the interference between different stimuli that is commonly observed in conventional MF sensors, 10 in addition to fabricating cost-effective sensors on a deformable substrate. Development of MF sensors that transduce different stimuli into separate signals can intrinsically minimize signal interference, thus allowing for sensitive detection of multiple parameters, such as temperature and pressure, in a single device without decoupling analysis. Many power-

A High‐Performances Flexible Temperature Sensor Composed of Polyethyleneimine/Reduced Graphene Oxide Bilayer for Real‐Time Monitoring

“…It might be caused by the redissolution phenomenon of PEI and GO during dipping in the L(+)‐AA solution, and therefore the PEI penetrated into the graphene interlaced sheets structure, showing good compatibility. [11b,25]…”

“…When the PEI impregnated rGO sheets are relatively close to each other, the carriers on the rGO sheets can break through the barrier and transfer to the adjacent rGO sheet via the tunneling effect. [11b] The special structure modified by PEI benefits the above‐mentioned carrier hopping and tunneling dominated temperature‐sensitive mechanism and therefore increases the sensitivity of sensor. Moreover, PEI have enhanced the adhesion of rGO sensitive film to the substrate, so that it remains stable contact and does not detach from the substrate during the immersion reduction process and bending process.…”

“…To date, some researches on skin‐attachable temperature sensors were reported, in which different kinds of materials, including metal nanoparticles/nanowires, graphene, carbon nanotubes (CNTs), polymers (such as poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS)),[5a,10,12,14] and others, have been explored as temperature sensing materials. Among various materials, graphene and its derivatives are wildly applied in temperature sensors owing to its outstanding electrical and thermal properties .…”

Comparative Studies on Polyurethane Composites Filled with Polyaniline and Graphene for DLP-Type 3D Printing

“…Polyurethane (PU) and its composites are thermosetting polymers, meaning that the PU-based composites can exhibit the properties of the thermoplastic polymer and the properties of the elastomer at the same time. Moreover, PU is extremely resistant to water, oil, heat, fire, ozone, and corrosion [11][12][13][14][15][16][17][18]. Therefore, the demand for using PU is rapidly growing in various applications, such as protective films, shoes, foams, automotive parts, biomedical devices, adhesives, coatings, and so forth [11][12][13][14][15][16][17][18].…”

Physical sensors for skin‐inspired electronics

“…The thermoelectric effect is widely present in semiconductors and conductors, wherein the effect of semiconductors is more pronounced. In recent years, some new thermoelectric materials (eg, organic semiconductors, conductive polymers, graphene, and CNTs) have received extensive attention. Based on organic thermoelectric materials (PEDOT:PSS), Zhang reported a flexible temperature sensor with an accurate resolution of 0.1 K (Figure E) .…”