Rupture stress of liquid metal nanoparticles and their applications in stretchable conductors and dielectrics

Abstract

Few works had systematically investigated the relationship between the rupture stress of the oxide shell and the diameter of liquid metal nanoparticles (LMNPs). Here, we fabricated a series of elastomer/LMNPs composites, which were based on various polyurethanes with different shore hardness and LMNPs with different diameters, to systematically study the rupture stress of LMNPs. We established a reliable and guidable relationship between the stress–strain curves of elastomers with different shore hardness and rupture stress of LMNPs with various diameters by both experiments and numerical calculations. Based on this guidance, we can facilely prepare stretchable conductors with remarkable stretchability and conductivity (i.e., 24,130 S · cm−1 at 500% strain) and stretchable dielectrics with excellent stretchability and permittivity (i.e., dielectric constant of 76.8 with 580% strain) through controlling the shore hardness of elastomers and diameter of LMNPs. This work will facilitate the systematic study of LMNPs and expand their use in stretchable electronics.

Multifunctional liquid metal polymer composites

“…Both mixtures were then mixed with a supplemental uncured polymer in a planetary mixer to reach their desired loading percentages. Other research has exemplified the use of another solvent, dimethylformamide (DMF), to produce EGaIn particles in the sub‐micron range as well 66 . The researchers used a polyurethane material as the matrix for the nanoparticles and were able to reach particle sizes as small as 300 nm.…”

“…Various stress–strain curves of polyurethanes (PU) are comparatively plotted. Reproduced with permission, 66 copyright 2021, Springer Nature…”

“…Composites with larger particles can be readily activated while smaller LM particles require higher force to rupture the oxide shell. For submicron LM particles, the rupture stress versus diameter relationship has been determined 66 . They found that the activation stress was inversely proportional to the diameter of the LM droplets, meaning larger droplets ruptured with less stress, calculated as shown in Equation (). where S is the activation stress and d is the LM particle diameter.…”

“…For submicron LM particles, the rupture stress versus diameter relationship has been determined. 66 They found that the activation stress was inversely proportional to the diameter of the LM droplets, meaning larger droplets ruptured with less stress, calculated as shown in Equation (1).…”

Liquid Metal Based Nano-Composites for Printable Stretchable Electronics

“…Although the oxides can change the material composition to improve interfacial wetting, the intrinsically fragile oxide shell (usually 0.7–3 nm) [ 32 ] stabilized LM particles are susceptible to rupture or leakage under strain or pressure stimuli [ 33 , 34 ]. To address this concern, surface ligand modification is potential solution to enable mechanical property and chemical function enhancement of the oxide layer.…”