Stretchable fine fiber with high conductivity fabricated by injection forming

Abstract

Stretchable conductors are necessary to realize soft and rubbery electronics. A stretchable fine fiber with high conductivity was fabricated by a injection forming. The fiber is made of silicone series conductive adhesive containing Ag flake fillers. The fiber has uniform diameter without any substrate and has very long length by the injection forming method. The diameters can be controlled by changing the bore diameter of the injection needle. Furthermore, the fine fiber, 230 μm in diameter, maintains excellent conductivity under cyclic tensile stress. The conductivity is approximately 470 S/cm without tensile stress and maintains over 90 S/cm under cyclic tensile test which is stretched up to 10% strain. The result exhibits a great potential of the conductive fine fiber as a stretchable conductor.

Fiber‐Based Wearable Electronics: A Review of Materials, Fabrication, Devices, and Applications

“…Some of them are made from CNTs, metals or metal alloys like copper, silver, nickel alloys, stainless steel; others are made from dielectric textiles by surface coating, plating, embroidery, printing, and lamination. Thus there are many hybrid or composite structures, including reduced graphene oxide/nylon yarn, graphene‐ferroelectric hybrid electrode, functional coatings on yarn, Poly(styrene‐ β‐isobutylene‐ β‐styrene)‐poly(3‐hexylthiophene) (SIBS‐P3HT) conducting composite fibers, Ag‐silicone fibers, fibers containing liquid metal alloy like eutectic gallium indium (EGaIn) injected into the core of stretchable hollow fibers composed of a triblock copolymer, SEBS resin (EGaIn in SEBS resin), a conductive composite mat of silver nanoparticles and rubber fibers, and twisted graphene yarns …”

“…The first approach relies on the development of new stretchable and elastic conductive materials, such as (1) graphene elastomeric composites: graphenes in polydimethylsiloxane (PDMS) or well controlled graphene on PDMS substrates, (2) carbon nanotube elastic materials: SWNT elastic conductor, MWNT/Ag composites in a polystyrene‐polyisoprene‐polystyrene matrix, and heavily‐twisted carbon nanotube ropes, (3) organic elastomer‐like conductor based on polyaniline (PANI) conducting polymer, and (4) PEDOT:PSS/PDMS composites, (5) (liquid) metal films or particles (e.g. eutectic gallium indium, gold or silver in/on elastomeric membranes or fibers. Those organic elastic conductors normally have an electric resistivity in the order of KΩ cm thus do not have sufficient conductivity to work as elastic connecting wires in integrated circuits .…”

Three-dimensionally deformable, highly stretchable, permeable, durable and washable fabric circuit boards

“…The stretchability has been increased by either structural conversion or using organic materials from approximately 3% (SiNW on PDMS substrate [110]) to more than approximately 400% (wrinkled graphene on PDMS substrate [71]). The relative change in electrical resistance varies from approximately 2.1% (horseshoe pattern on PDMS substrate [108]) to approximately 7300% (Ag-MWNT-SIS nanocomposite film [73]), which may hinder the use as conductive tracks in stretchable circuit boards, in particular, for low-impedance electronic components or high-precision measurements [96,97]. By contrast, the knitted FCB has exhibited an extraordinarily electrical stability with almost no change in electrical resistance up to strain of 300% in unidirectional tensile deformation.…”

“…PDMS). The conductivity for those organic elastic conductors, except MWNT/Ag composite (conductivity: 3700 S cm −1 ) [73], is too low (conductivity: less than 1000 S cm −1 ) to perform as electrical wirings, particularly for integrated circuits [96][97][98]. More crucially, most of such organic conductors, except polymeric ionic conductors [99], drop their conductivity by at least several orders of magnitude even within 10% strain [75].…”

Impact of geometry on stretchable meandered interconnect uniaxial tensile extension fatigue reliability

“…Reviewing the stretchable technologies developed in the recent years [3][4][5][6][7][8][9][10] we find no stretchable, conductive, composite elastomers that fulfill these requirements all at once. Only structured metals (meanders [11][12][13][14], meshes [15], yarns or buckled films [16]), forming a stretchable interconnect exhibit electro-mechanical properties that can fulfill the above mentioned requirements.…”