Thermoplastic Elastomer Systems Containing Carbon Nanofibers as Soft Piezoresistive Sensors

Abstract

Soft, wearable or printable strain sensors derived from conductive polymer nanocomposites (CPNs) are becoming increasingly ubiquitous in personal-care applications. Common elastomers employed in the fabrication of such piezoresistive CPNs frequently rely on chemically cross-linked polydiene or polysiloxane chemistry, thereby generating relatively inexpensive and reliable sensors that become solid waste upon application termination. Moreover, the shape anisotropy of the incorporated conductive nanoparticles can produce interesting electrical effects due to strain-induced spatial rearrangement. In this study, we investigate the morphological, mechanical, electrical, and electromechanical properties of CPNs generated from thermoplastic elastomer (TPE) triblock copolymer systems containing vapor-grown carbon nanofiber (CNF). Modulus-tunable TPE gels imbibed with a midblock-selective aliphatic oil exhibit well-behaved properties with increasing CNF content, but generally display nonlinear negative piezoresistance at different strain amplitudes and stretch rates due to nanofiber mobility upon CPN strain-cycling. In contrast, a neat TPE possessing low hard-block content yields a distinctive strain-reversible piezoresistive response, as well as low electrical hysteresis, upon cyclic deformation. Unlike their chemically cross-linked analogs, these physically cross-linked and thus environmentally benign CPNs are fully reprocessable by thermal and/or solvent means.

Thermoplastic elastomer composite filaments for strain sensing applications extruded with a fused deposition modelling 3D printer

“…The rapid advancement in the field of soft robotics and wearable electronic devices calls for the development of soft, stretchable sensors that are able to conform to complex structures and geometries [1][2][3][4][5][6][7][8]. Typically, soft sensor materials are extrinsic conductive composites, consisting of an elastomeric material and a conductive filler like graphite, carbon black, carbon nanotubes, nanofibers or graphene [9][10][11][12]. In the case of soft material strain sensors, the stretchability is a crucial characteristic of the sensor performance.…”

Fabrication and characterization of vapor grown carbon nanofiber reinforced flexible polymer composites

“…Although, SEBS can be filled with various nanofillers [26][27][28][29], depending on our experience and previous studies CNFs are one of the most suitable materials [16,18]. Their contribution to mechanical property improvement stemmed from their unique structure.…”

“…Mechanical and electromechanical properties were investigated. Mechanical properties were reported to increase by the addition of CNFs [16].…”

“…In all these applications flexibility is particularly crucial for microelectro-mechanical systems (MEMS), sensors and actuators whose basic function is depended on their electromechanical properties. For the flexible electronics various polymers can be used as basic or auxiliary components including inherently conductive polymers [1][2][3][4][5], thermoplastics [6][7][8], thermosets [9,10], elastomers [11][12][13], and thermoplastic elastomers [14][15][16] or polymer blends [17]. In this case, in addition to electrical character, mechanical character plays an important role during the functioning and not only flexible but also stretchable, bendable, twistable materials are required with high resilience and satisfying recoverability after unloading the mechanical effect [18].…”

1st Symposium on Polydopamine and NanoTech Poland 2018: Conference Report

“…He also presented thermoplastic elastomers where the end blocks were mechanically uncompromised and capable of stabilizing a midblock-rich network in various environments. His final topic was about the selective sulfonation of polydiene and polystyrene midblocks in triblock copolymers, which are analogous to commercial midblock-sulfonated multiblock copolymers that can be successfully used in water desalination, gas separation, organic photovoltaics, and ionic polymer–metal composites [32,33,34].…”