SCIENTIA SINICA Informationis, Volume 48 , Issue 6 : 650-669(2018) https://doi.org/10.1360/N112018-00117

Recent advances in flexible self-healing materials and sensors

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  • ReceivedMay 7, 2018
  • AcceptedMay 18, 2018
  • PublishedJun 12, 2018


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  • Figure 1

    (Color online) Schematic of self-healing mechanism of polymers [32]@Copyright 2017 John Wiley and Sons. protectłinebreak(a) Intrinsic; (b) extrinsic

  • Figure 2

    (Color online) Schematic of self-healing of conductive material/polymer composites: (a) Schematic of self-healing via embedding liquid conductive materials capsules [67]@Copyright 2011 John Wiley and Sons. (b) Schematic of self-healing of AgNWs/(bPEI/PAA-HA) composite with the aid of water [19]@Copyright 2012 John Wiley and Sons. (c) Schematic of the microstructure of $\mu$Ni/L composite and the process of electrical self-healing. 1. Undamaged material; 2. completely fractured material; 3. Self-supporting material with its fractured surfaces contact for 15 s; 4. Flexed material after being healed for 5 min, showing its mechanical strength and flexibility [14]@Copyright 2012 Springer Nature

  • Figure 3

    (Color online) Self-healing piezoresistive force sensor based on $\mu$Ni/L composite [14]@Copyright 2012 Springer Nature. (a) Current-voltage curve of a commercial LED using self-healing $\mu$Ni/L composite as conducting wire. Inset: optical photograph of the circuit taken at 2.5 V (scale bar, 10 mm). (b) and (c) Self-healing of the (b) electrical and (c) mechanicalperformance of $\mu$Ni/L composite. (d) Electrical response of the flexion sensors based on $\mu$Ni/L composite in free-standing modes and self-adhered modes on PET substrate. (e) Electrical response of the parallel-plate structured tactile sensor based on $\mu$Ni/L composite. (f) Self-healing flexion and tactile sensor circuit schematic and the optical photograph of a fully articulated wooden mannequin with its elbow and palm region mounted with the flexion and tactile sensor circuits

  • Figure 4

    (Color online) Real-time monitoring of human motions using the superelastic strain sensor based on self-healing SWNT/PVA-borax hydrogel composite [78]. (a) Bending and release of the finger; (b) bending of the knee; (c) bending and release of the neck; (d) bending and release of the elbow

  • Figure 5

    (Color online) Self-healing piezoresistive stress/strain sensor based on conductive polymer [15]@Copyright 2017 John Wiley and Sons. (a) Schematic of the self-healing mechanism; (b) self-healing efficiency of mechanical property; protectłinebreak(c) electrical self-healing property; (d) schematic of the preparation of wearable sensor via 3D printing technique; protectłinebreak (e) real-time human motion monitoring system based on the wearable sensor and smart phone

  • Figure 6

    (Color online) SWNT/L composite [91]@Copyright 2016 John Wiley and Sons. (a) Schematic of the structure; (b) and (c) optical photographs; (d) and (e) temperature sensing performance and the optical photographs showing the measurement procedure; (f) electrical self-healing performance

  • Figure 7

    (Color online) Self-healable flexible gas sensor based on MWNT/PEM composite film [21]@Copyright 2015 John Wiley and Sons. (a) Schematic showing the self-healing procedure of the gas sensor; (b)–(e) SEM images of MWNT/PEM film with a cut before and after being healed; (f) electrical self-healing property; (g) the sensing sensitivity of MWNT/PEM film to 25 ppm ${\rm~NH}_{3}$ after healing for different times

  • Figure 8

    (Color online) Self-healing flexible multifunctional sensor [22]@Copyright 2015 John Wiley and Sons. protectłinebreak(a) Schematic of the device structure and its optical photograph; SEM images of the microstructure of (b1)–(b4) PU substrate, (c1)–(c4) PU/$\mu$Ag composite, and (d1)–(d4) AuNP film with a cut showing the self-healing procedure; (e) electrical response to bending deformation; (f) electrical response to stretching deformation; (g) electrical response to VOC n-octanol; (h) electrical response to temperature variation

  • Figure 9

    (Color online) The overall experimental strategy relating to the flexible self-healable multifunctional sensor for human health monitoring application [98]@Copyright 2016 American Chemical Society. (a) Schematic of the structure; protectłinebreak(b) schematic of the molecular structure used for the functionalization of AuNP; (c) demonstration of the self-heal of the sensor under 3 different damage modes

  • Table 1   Summary of the self-healing performance of typical polymers $^{\rm~a)}$
    Material Mechanical Healing Healing Healing Ref.
    strength mechanism condition efficiency (%
    3M4F 121 MPa/ Thermal reversible 120${^\circ}$C$\sim$150${^\circ}$C 41$\sim$50 [34]
    Compression DA reaction (N$_{2})$/2 h$~\to~$RT
    2MEP4F 121 MPa/ Thermal reversible 115${^\circ}$C/30 min 80 [35]
    Compression DA reaction $\to~$40${^\circ}$C/6 h
    DCPD based 85 MPa/par Compression Thermal reversible 120${^\circ}$C(Ar)/20 h 46 [36]
    polymer DA reaction
    Epoxy based par rubber 0.5 MPa/par Stretch Disulfide bond 60${^\circ}$C/1 h 95 [41]
    PU rubber 3.9 MPa/par Stretch Disulfide bond Visible light/ 24 h 97 [42]
    Ru/PBD 0.4 MPa/par Stretch C-C double bond 20 kPa/1 h 100 [47]
    CF/polyimine 140 MPa/par Bending Imine bond 121${^\circ}$C/45 MPa 100 [46]
    M1-TEGMEMA Acylhydrazone bond 100${^\circ}$C/24 h 100 [44]
    Fatty acid based SR 2 MPa/par Stretch Hydrogen bond RT/3 h 100 [50]
    PDMS-COOH$_{2}$ par based SR 0.4 MPa/par Stretch Hydrogen bond 80${^\circ}$C/16 h 100 [53]

    a) 3M (maleimide monomor); 4F (furan monomer); RT (room temperature); 2MEP (1, 8-Bis(maleimido)-1-ethylpropane); DCPD (dicyclopentadiene); PU (polyurethane); PBD (polybutadiene); CF (carbon fiber); M1 (acylhydrazone monomer); TEGMEMA (triethylene glycol methylether methacrylate); SR (supermolecular rubber); PDMS (polydimethylsiloxane oligomers); COOH (carboxyl)

  • Table 2   Summary of typical research about flexible self-healing sensors$^{\rm~a)}$
    Material Healing par mechanism Healing condition/par efficiency Application Ref.
    MDPB-TDF/ S-CCTO Self-healing of SWNT 105${^\circ}$C/30 min: Capacitive [13]
    driven by thermal electrical$\sim~$89%; force sensor
    reversible DA reaction mechanical$\sim~$86%
    $\mu~$Ni/L Hydrogen bond 50 kPa/15 s: electrical$\sim~$90% Piezoresistive [14]
    50${^\circ}$C/10 min: mechanical$\sim~$100% force sensor
    rGO/PBS B-O dative bond & RT/10 min: par electrical$\sim~$90%; Piezoresistive [26]
    hydrogen bond mechanical$\sim~$80% force sensor
    SWNT/ PVA-borax Hydrogen bond RT/3.2 s: electrical$\sim~$98% Piezoresistive [78]
    force sensor
    m-PCL/GO/ AgNWs Hydrogen bond 80${^\circ}$C/3 min: par electrical$\sim~$80%; Piezoresistive [79]
    mechanical$\sim~$100% force sensor
    CNT-Fe$^{3~+~}$/PDA@ENR Metal coordination bond RT/24 h: par electrical$\sim~$100%; Piezoresistive [80]
    mechanical$\sim~$89.3% force sensor
    CNTs@(PEI@CNC)/ Hydrogen bond Hot-press: par electrical$\sim~$100%; piezoresistive [81]
    XNBR mechanical$\sim~$83% force sensor
    C-CNC@GA@Ca$^{2+}$ Hydrogen & RT/30 s: par electrical$\sim~$100%; Piezoresistive [82]
    @CNTs/ENR metal coordination bond mechanical$\sim~$90% force sensor
    C-CNC@CT@CNTs/ENR Hydrogen bond RT/15 s: par electrical$\sim~$100%; Piezoresistive par [83]
    mechanical$\sim~$100% force sensor
    Amylopectin par hydrogel Hydrogen bond RT/3 s: electrical$\sim~$99.3%; Piezoresistive [84]
    RT/5 min: mechanical$\sim~$98.4% force sensor
    PVA-PEDOT: PSS Hydrogen bond 80${^\circ}$C $\to~-$20${^\circ}$C: par electrical$\sim~$100%; Piezoresistive [85]
    mechanical$\sim~$85% force sensor
    PVA-PVP/CNC-Fe$^{3~+~}$ Ionic coordination bond RT/5 min: par electrical$\sim~$100%; Piezoresistive [86]
    mechanical$\sim~$100% force sensor
    $\kappa~$-carrageenan/PAAm Thermal-reversibleg 90${^\circ}$C/20 min: par electrical$\sim~$99.2%; Piezoresistive [87]
    $\kappa~$-carrageenan mechanical$\sim~$100% force sensor
    PEG-PAA Metal coordination & RT/2 h: electrical $\sim~$100% par RT/12 h: Piezoresistive [88]
    Hydrogen bond mechanical$\sim~$96.8% force sensor
    PANI-PAA-PA Hydrogen bond & Slight pressure/24 h: electrical$\sim~$99%; Piezoresistive [89]
    electrostatic interaction mechanical$\sim~$99% force sensor
    Graphene/PU Thermal reversible Microwave/5 min$~\to~$65${^\circ}$C/5 h: par Piezoresistive [90]
    DA reaction electrical$\sim~$75%; mechanical$\sim~$100% force sensor
    PAA-Fe$^{3~+~}$/DCh-PPy Ionic interaction RT/1 min: electrical$\sim~$96% par Piezoresistive [15]
    RT/2 min: mechanical$\sim~$100% force sensor
    PDMAA-PVA/rGO Hydrogen bond RT/12 h: par electrical$\sim~$89.6%; Piezoresistive [25]
    mechanical$\sim~$100% force sensor
    SWNT/L Hydrogen bond RT/1 h: electrical$\sim~$100% Temperature sensor [91]
    P(BMA-co-LMA)/MWNT C-C double cond 60${^\circ}$C/3 h: par electrical$\sim~$98%; Temperature sensor [92]
    MWNT/PEM Hydrogen bond & Water/30 min: par electrical $\sim~$91%; Gas sensor [21]
    electrostatic interaction mechanical$\sim~$100%

    a) S-CCTO (surface-modified CaCu3Ti4O12); MDPB (1, 1'-(methylene di-4, 1-phenylene) bismaleimide); TDF (2, 2'-(Thiodimethylene) difuran); PBS (polyborosiloxane); PVA (polyvinyl alcohol); m-PCL (poly( 3-caprolactone) microspheres); PDA (polydopamine); ENR (epoxidized natural rubber); PEI (polyethyleneimine); C-CNC (carboxyl cellulose nanocrystals); XNBR (carboxylated nitrile rubber); GA (gelatin); CT (chitosan); PEDOT:PSS (poly(3, 4-ethylenedioxythiophene):polystryrene sulfonate); PVP (polyvinyl pyrrolidone); PAAm (polyacrylamide); PEG (polyethylene glycol); PAA (poly(acrylic acid)); PANI (polyaniline); PA (phytic acid); DCh (double-bond decorated chitosan); PPy (polypyrrole); PDMAA (poly(N, N-dimethylacrylamide)); P(BMA-co-LMA) (poly(butyl methacrylate-co-lauryl methacrylate)); PEM (polyelectrolyte multilayer)