Low‐Molecular‐Weight Supramolecular‐Polymer Double‐Network Eutectogels for Self‐Adhesive and Bidirectional Sensors

Abstract

Ionic conducting eutectogels have attracted enormous attention as an alternative to the conventional temperature-intolerant hydrogels and costly ionic liquid gels in constructing flexible electronic devices. However, current eutectogels prepared via cross-linked polymer or low-molecular-weight gelators suffer from limited stretchability and insufficient surface-adaptive adhesion. Herein, a low-molecular-weight supramolecular network is introduced into a covalent polymer network in a eutectogel architecture, and a novel supramolecularpolymer double-network (SP-DN) strategy is demonstrated to fabricate conductive SP-DN eutectogels with high stretchability (>4000% elongation) and toughness (≈800 J m −2 ), as well as self-healing, self-adhesive and anti-freezing/ anti-drying characteristics. These unique features lead to the successful realization of SP-DN eutectogels in wearable self-adhesive strain sensors, which can conformally deform with the skin and dynamically monitor body movements with high sensitivity and long-term stability over a wide temperature range (−40 to 60 °C). Furthermore, the strain sensors can accurately detect body movements along two opposite directions (bend up or bend down), which are rarely reported in the literature. Distinct from the widely explored polymer double-network (P-DN) hydrogels, the developed SP-DN eutectogel platform is capable of well-regulating molecular-scale noncovalent and covalent interactions, providing a paradigm for the creation of smart soft materials with versatile performance and high environmental adaptability.

Strong and Tough Conductive Organo‐Hydrogels via Freeze‐Casting Assisted Solution Substitution

“…As exhibited in Figure , the most sought‐after properties of flexible electronic engineering materials, including tensile strength, uniform strain, toughness, and conductivity, were selected as the comparison parameters (See Table S1, Supporting Information for detailed data). In comparison, we found that some hydrogels from other works showed exceptional performance regarding a particular property, such as the ultra‐high‐strength hydrogel from natural white wood as the raw material, [ 35 ] super‐stretchable hydrogel of eutectic dual network, [ 36 ] and highly conductive hydrogel incorporating sulfuric acid. [ 37 ] Nonetheless, our organo‐hydrogel showed an exceptional all‐around performance with a high average strength of 5.75–6.77 MPa, high uniform strain of 1400–1710%, and high conductivity of 1.3–6.5 S m −1 .…”

Mxene Reinforced Supramolecular Hydrogels with High Strength, Stretchability, and Reliable Conductivity for Sensitive Strain Sensors

“…and 260-370%, respectively (Figure 7B; Figure S7, Supporting Information), it was comparable to or a bit higher than the mechanosensation behavior of the hydrogel-based sensors reported. [6,13,20] PNAGA/MXene displayed higher sensitivity in the range of 0-185% than the MXene hydrogels reported. [17] The results verified that PNAGA/MXene hydrogel displayed great sensitivity and stability that increased with the increase of strain.…”

“…However, the poor mechanical properties and limitation of sensitivity have paved the related researchers devoting to search and develop conductive fillers and polymer matrices for new types of conductive hydrogels including supramolecular hydrogels, double cross-linked hydrogels, nanocomposite hydrogels, and zwitterionic hydrogels. [19][20][21][22] Conductive hydrogels are engineered with multifunctional, high stretchability, anti-freezing, stimuli-responsive, and self-healing by designing the cross-linked network, chemical covalent bonds, or physical reversible dynamic bonds. [23][24][25][26] Furthermore, to achieve the feasibility and accuracy of conductive hydrogel sensors, the conductive networks should be enough stable to maintain high sensitivity and linearity at high strain, [27] which mostly depends on the interactions between conductive fillers and flexible polymer matrix.…”

Tough and Ultrastretchable Liquid‐Free Ion Conductor Strengthened by Deep Eutectic Solvent Hydrolyzed Cellulose Microfibers

“…Similar to many reported strain sensors, the GF was divided into three regions: when the strain was 0-300%, the GF was 1.46; when the strain was 300-800%, the GF was 2.59; when the strain was 800-1300%, the GF was 3.71. Both the large work range and high sensitivity of PDES/CMFs-1 IC surpass the values of many other sensors reported elsewhere [21,[45][46][47][48]57,58] and hence demonstrated huge application potentials. Furthermore, ΔR/R 0 under small strains (5%, 10%, 20%, and 50%) and large strains (100%, 200%, and 500%) were also recorded as shown in Figure 4b,c, respectively.…”

“…Overall, PDES/CMFs ICs achieved both superb stretchability and excellent tensile strength, compared to previously reported DES based gels and elastomers as summarized in Figure 1i. [22,24,28,[44][45][46][47][48][49][50][51] We speculated that the enhanced mechanical properties of PDES/CMFs ICs were ascribed to the load transfer mechanism. [52][53][54][55][56] As shown in Figure 2, in the initial state, the CMFs were uniformly and randomly distributed in the PAA network.…”