Mechanically Strong and Multifunctional Hybrid Hydrogels with Ultrahigh Electrical Conductivity

Abstract

Stretchable conductive hydrogels with simultaneous high mechanical strength/modulus, and ultrahigh, stable electrical conductivity are ideal for applications in soft robots, artificial skin, and bioelectronics, but to date, they are still very challenging to fabricate. Herein, sandwich‐structured hybrid hydrogels based on layers of aramid nanofibers (ANFs) reinforced polyvinyl alcohol (PVA) hydrogels and a layer of silver nanowires (AgNWs)/PVA are fabricated by electrospinning combined with vacuum‐assisted filtration. The hybrid ANF‐PVA hydrogels exhibit excellent mechanical properties with the tensile modulus of 10.7–15.4 MPa, tensile strength of 3.3–5.5 MPa, and fracture energy up to 5.7 kJ m−2, primarily attributed to the strong hydrogen bonding interactions between PVA and ANFs and in‐plane alignment of the fibrous structure. Rational design of heterogeneous structure endows the hydrogels with ultrahigh apparent electrical conductivity of 1.66 × 104 S m−1, among the highest electrical conductivities ever reported so far for conductive hydrogels. More importantly, this ultrahigh conductivity remains constant upon a broad range of applied strains from 0–90% and over 500 stretching cycles. Furthermore, the hydrogels exhibit excellent Joule heating and electromagnetic interference shielding performances due to the ultrahigh electrical conductivity. These mechanically strong, hybrid hydrogels with ultrahigh and strain‐invariant electrical conductivity represent great promises for many important applications such as flexible electronics.

Ultra‐High Electrical Conductivity in Filler‐Free Polymeric Hydrogels Toward Thermoelectrics and Electromagnetic Interference Shielding

“…a) The swelling ratios and b) the electrical conductivities of PEDOT:PSS hydrogel /EMIM‐TFSI and PEDOT:PSS hydrogel /EMIM‐Cl vary with the glycerol concentration. c) Comparison of the highest electrical conductivities of PEDOT:PSS hydrogel /EMIM‐TFSI with literature reported values (: without conductive filler; [ 12,18,24,27 ] : Ag‐based hydrogel; [ 28,29 ] : graphene‐based hydrogel; [ 30 ] : CNT based hydrogel [ 17,31 ] ). d) Illustration of the formation of pristine PEDOT:PSS hydrogel formed in water, IL doped PEDOT:PSS hydrogel formed in water, IL doped PEDOT:PSS hydrogel formed in glycerol aqueous solution.…”

“…[ 39 ] Ye and Zhu reported a silver nanowire and polymer hybrid hydrogel with a maximum SSE of 173 dB mm −1 . [ 29 ] The commercial requirements were >15 dB for computers, >40 dB for the electronic control unit, and >50 dB for sensors as reported in the literature. [ 39,42 ] The EMI shielding efficiency for PEDOT:PSS hydrogel /EMIM‐TFSI/glycerol‐90 with a typical thickness of 46 µm was 54 dB, which could satisfy the commercial requirements.…”

“…The high electrical conductivity resulted in high areal thermoelectric output power of ≈3 times higher than that of DMSO doped PEDOT:PSS hydrogels reported previously, [15] which also resulted in high SSE that was about an order in magnitude higher than that of state-of-the-art conductive hydrogels in literature. [29,39] Theoretical calculation indicated that the high electrical conductivity of these hydrogels was attributed to the nano-phase segregation derived from the partially replacing of PSS with IL anions. The free energy of ion exchange was strongly related to the electrical and mechanical properties.…”

“…Therefore, the thickness was smaller for hydrogels formed in the aqueous solution with higher glycerol concentration when the initial PEDOT:PSS films were the same (Figure 3d). [12,18,24,27] : Ag-based hydrogel; [28,29] : graphene-based hydrogel; [30] : CNT based hydrogel [17,31] ). d) Illustration of the formation of pristine PEDOT:PSS hydrogel formed in water, IL doped PEDOT:PSS hydrogel formed in water, IL doped PEDOT:PSS hydrogel formed in glycerol aqueous solution.…”

Co‐MnO2 Nanorods for High‐Performance Sodium/Potassium‐Ion Batteries and Highly Conductive Gel‐Type Supercapacitors

“…However, there are many problems needed to be solved urgently, such as poor mechanics properties, and inferior ionic conductivity (10 −5 –10 −8 S cm −1 ). [ 6 ] Actually, doping inorganic substances, like borax and FeCl 3 , can not only improve the conductivity, but also cross‐link the PVA to form a polymer network and then improve the mechanical properties. [ 7 ]…”