Herein, we report a de novo chemical design of supramolecular polymer materials (SPMs-1-3) by condensation polymerization, consisting of (i) soft polymeric chains (polytetramethylene glycol and tetraethylene glycol) and (ii) strong and reversible quadruple H-bonding cross-linkers (from 0 to 30 mol %). The former contributes to the formation of the soft domain of the SPMs, and the latter furnishes the SPMs with desirable mechanical properties, thereby producing soft, stretchable, yet tough elastomers. The resulting SPM-2 was observed to be highly stretchable (up to 17 000% strain), tough (fracture energy ∼30 000 J/m), and self-healing, which are highly desirable properties and are superior to previously reported elastomers and tough hydrogels. Furthermore, a gold, thin film electrode deposited on this SPM substrate retains its conductivity and combines high stretchability (∼400%), fracture/notch insensitivity, self-healing, and good interfacial adhesion with the gold film. Again, these properties are all highly complementary to commonly used polydimethylsiloxane-based thin film metal electrodes. Last, we proceed to demonstrate the practical utility of our fabricated electrode via both in vivo and in vitro measurements of electromyography signals. This fundamental understanding obtained from the investigation of these SPMs will facilitate the progress of intelligent soft materials and flexible electronics.

Stretchable conductors are the basic building blocks of advanced flexible electronic devices, such as flexible display, skin-like sensors, stretchable batteries, soft actuators and so forth. [1][2][3][4][5][6][7][8][9][10] They are used in a vast number of soft and stretchable devices developed in recent years, including biointerfacing electrodes, [11][12][13][14][15] transistors, [16][17][18] mechanical sensors, [19][20][21][22] energy devices [23][24][25][26] and many more. [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] To meet most application requirements, stretchable conductors need to remain conductive under tensile strain of more than 100%, and even more importantly, to show stable performance in terms of interfacial adhesion between conductive metal film and the supporting polymer substrate.[1] Current methods to achieve stretchable conductors generally fall into two categories. One involves a structural design strategy, where the conducting material is designed with specific structures/topographies including serpentines, [46][47][48][49][50][51][52] wrinkles, [53,54] meshes, [55][56][57][58] and microcracks. [59][60][61][62][63] The other strategy relies on intrinsic stretchability of Stretchable conductors are the basic units of advanced flexible electronic devices, such as skin-like sensors, stretchable batteries and soft actuators. Current fabrication strategies are mainly focused on the stretchability of the conductor with less emphasis on the huge mismatch of the conductive material and polymeric substrate, which results in stability issues during long-term use. Thermal-radiation-assisted metal encapsulation is reported to construct an interlocking layer between polydimethylsiloxane (PDMS) and gold by employing a semipolymerized PDMS substrate to encapsulate the gold clusters/atoms during thermal deposition. The stability of the stretchable conductor is significantly enhanced based on the interlocking effect of metal and polymer, with high interfacial adhesion (>2 MPa) and cyclic stability (>10 000 cycles). Also, the conductor exhibits superior properties such as high stretchability (>130%) and large active surface area (>5:1 effective surface area/geometrical area). It is noted that this method can be easily used to fabricate such a stretchable conductor in a wafer-scale format through a one-step process. As a proof of concept, both long-term implantation in an animal model to monitor intramuscular electric signals and on human skin for detection of biosignals are demonstrated. This design approach brings about a new perspective on the exploration of stretchable conductors for biomedical applications.