# Shape Memory-Enhanced Electrical Self-Healing of Stretchable Electrodes
## 1 Introduction  
Self-healing polymers are one set of very important bio-mimetic materials, which have been catching increasing academic and industrial interests over the recent years. The underlying mechanisms towards heal-ability in the polymeric systems included various types of reversible bonding, such as hydrogen and disulfide bonding [1, 2]. Unlike the previous reports on the self-healable polymers commonly requiring complex macro-molecular design and synthesis, shape memory-assisted self-healing was explored for a thermoplastic shape memory polymers matrix containing the healing reagent [3]. In this shape memory-assisted self-healing polymeric systems, the polycaprolactone (PCL) was chosen as the healing reagent due to the programmable crystallization/melting transitions, compatibility with the polymer matrix and the moving ability of the molecules in the melted states [4]. For instance, the PCL was integrated into an epoxy or polyurethane polymeric matrix via direct physical blending or electro-spinning to nonwoven meshes [5]. The reversible thermal transitions at the aid of the shape memory effect enabled the scratches on the surfaces even in the scale of several micro-meters to heal under thermal stimulations. Furthermore, the integration of the conductive nano networks with intelligent polymers lead to flexible and stretchable electronics possessing multi-functionalities. For instance, [PERSON] et al. explored a dynamic cross-linked hydrogel featuring the stain-dependent conduction and the high stretch-ability, which was applied to detect human-motion. The conductive networks were constructed by carbon nanotubes (CNTs) and the strain sensing properties werecapable of self-healing [6]. [PERSON] et al. demonstrated a multiple hydrogen bonding network with the CNTs which exhibited extremely fast and repeatable self-healing ability with high healing efficiency of 93% [7]. Particularly, a multi-layer structure shape memory strain sensor was reported comprising a polyurethane fiber core, interconnected CNTs filament, and a polypyrrole cladding layer. The microcracks generated under strain endowed this fibriform sensor with the superior sensitivity, a wide detectable range and the ability to detect multimodal deformation and human motions [8]. [PERSON] et al. designed a two-way composite, which was comprised of an electroactive polymer providing actuation force and a traditional shape memory polymer to fix the temporary shapes due to the modulus changing abilities.  
Although shape memory assisted self-healing has been developed for several years, there are few reports on the heal-ability of the conductivity for the shape memory-based conductive composites. We embedded the AgNWs into an epoxy shape memory matrix and achieved multi-stimuli triggered self-healing effect, i.e., healing the surface cracks under electrical and thermal stimulations [9]. Herein, a novel shape memory-based stretchable healable electrode was explored. The resultant composites were capable of healing the damaged conduction as exposed upon the scratch under thermal stimulation. To be interested, we pre-stored the strain energy perpendicular to that of the scratch by taking advantage of the stretch-ability and shape memory effect. The healing efficiency was greatly enhanced due to the closure of the crack surfaces driven by the release of the strain energy. We called the \"pre-stored and release of the strain energy in order to improve the self-healing\" as the shape memory-enhanced self-healing. The studies provided a facial physical programming to optimize the behaviors of shape memory conductive composites and may greatly benefit the application of intelligent polymers in the field of functional flexible electronics.