Designing Hierarchical Soft Network Materials with Developable Lattice Nodes for High Stretchability

Abstract

Soft network materials (SNMs) represent one of the best candidates for the substrates and the encapsulation layers of stretchable inorganic electronics, because they are capable of precisely customizing the J‐shaped stress–strain curves of biological tissues. Although a variety of microstructures and topologies have been exploited to adjust the nonlinear stress–strain responses of SNMs, the stretchability of most SNMs is hard to exceed 100%. Designing novel high‐strength SNMs with much larger stretchability (e.g., >200%) than existing SNMs and conventional elastomers remains a challenge. This paper develops a class of hierarchical soft network materials (HSNMs) with developable lattice nodes, which can significantly improve the stretchability of SNMs without any loss of strength. The effects of geometric parameters, lattice topologies, and loading directions on the mechanical properties of HSNMs are systematically discussed by experiments and numerical simulations. The proposed node design strategy for SNMs is also proved to be widely applicable to different constituent materials, including polymers and metals.

Hybrid-Microstructure-Based Soft Network Materials with Independent Tunability of Mechanical Properties over Large Deformations

“…Different from the conventional SNMs which consist of a certain type of microstructure, the HMSNMs are constructed from two distinct types of microstructures along different principal directions. The triangular lattice topology is adopted here to avoid the undesired shear deformation while offering auxetic behavior. − In this work, the HMSNMs are supposed to be subjected to uniaxial tension along the X -axis, unless otherwise specified. To achieve biomimetic J-shaped stress–strain curves and relatively high stretchability, we employ horseshoe-shaped microstructures (indicated by blue horizontal microstructures in Figure a) as the building-block structures of HMSNMs in the loading direction. − Conversely, zigzag-shaped microstructures are utilized as the building-block structures in the transverse direction (i.e., oblique microstructures marked in orange), with reduced widths at turning sites to induce significantly negative Poisson’s ratios .…”