Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices.

Lightweight and elastic carbon materials have attracted great interest in pressure sensing and energy storage for wearable devices and electronic skins. Wood is the most abundant renewable resource and offers green and sustainable raw materials for fabricating lightweight carbon materials. Herein, a facile and sustainable strategy is proposed to fabricate a wood-derived elastic carbon aerogel with tracheid-like texture from cellulose nanofibers (CNFs) and lignin. The flexible CNFs entangle and assemble into an interconnected framework, while lignin with high thermal stability and favorable stiffness prevents the framework from severe structural shrinkage during annealing. This strategy leads to an ordered tracheid-like structure and significantly reduces the thermal deformation of the CNFs network, producing a lightweight and elastic carbon aerogel. The wood-derived carbon aerogel exhibits excellent mechanical performance, including high compressibility (up to 95% strain) and fatigue resistance. It also reveals high sensitivity at a wide working pressure range of 0-16.89 kPa and can detect human biosignals accurately. Moreover, the carbon aerogel can be assembled into a flexible and free-standing all-solid-state symmetric supercapacitor that reveals satisfactory electrochemical performance and mechanical flexibility. These features make the wood-derived carbon aerogel highly attractive for pressure sensor and flexible electrode applications.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201910292. important applications in wearable sensors, electronic skins, and flexible energy storage devices. Although carbon aerogels with good mechanical performances can be achieved from nanocarbon unites, their carbon precursors are nonrenewable, and the synthesis process of CNT, graphene, or their aerogels is high-cost and complicated.Considering the natural abundance, renewability, environmental friendliness, and low cost, biomass has been regarded as a renewable and sustainable carbon precursor for fabricating carbon aerogels. Up to now, several biomass-derived carbon aerogels have been successfully developed from gelatin, [16] winter melon, [17] protein, [18] bacterial cellulose, [19] and raw cotton. [20] However, those carbon aerogels show poor compressibility, elasticity, and fatigue resistance owing to the intrinsic random porous architecture and severe volume shrinkage at annealing or carbonization. Wood, as one of the most abundant biomass resources, demonstrates hierarchical tracheid structure that is composed of CNFs and amorphous matrix (lignin and hemicelluloses). [21] Owing to the compact structure (large amounts of additives and various interaction among tracheids or CNFs), natural wood is rigid and the tracheids are hard to be compressed and easily collapsed. Therefore, fabricating compressible and elastic conductive carbon aerogel from original wood tracheids is challenging. To solve this problem, Hu et al. [22] put forward a "top-down" stra...

Stretchable and tough hydrogels are highly required for various flexible devices. Liquid metal (LM) emerges as an attractive applicant in preparing functional hydrogels due to its unique features. However, the high fluidity of LM and incompatibility between LM and polymer matrix make it hard to fabricate tough hydrogels. Herein, inspired by the function of ligaments in biological structure, graphene oxide (GO) nanosheets are introduced to encapsulate LM droplets. GO nanosheets form strong interaction with both LM and polymer matrix to create a stable shell that prevents LM droplet from fracture and exudation to polymer network. The flexible LM/GO core–shell microstructure avoids phase separation and produces a tough hydrogel with stress of high up to 303 kPa at 1240% elongation. It also shows notch insensitivity and strong adhesion to various surfaces. This study opens the possibility of using LM in stretchable and tough hydrogels.

Compressible and elastic carbon aerogels with low density, excellent conductivity, high porosity, and chemical stability have attracted much attention in wearable energy storage and sensing devices. However, the mechanical performances of current carbon aerogels are usually limited due to undesirable structural engineering. Herein, an effective and sustainable route is proposed to fabricate a lightweight yet highly elastic carbon aerogel from a renewable nanounit. To realize this aim, mechanically strong cellulose nanocrystal (CNC) serves as the structural unit, while konjac glucomannan (KGM) links CNCs into continuous and orientally aligned layers with a wavy shape. The lamellar architecture and the interaction among CNC and KGM give rise to a lightweight carbon aerogel with ultrahigh structural stability and outstanding mechanical performance that is superior to those of graphene and carbon nanotube (CNT)-based carbon aerogels. Specifically, it can maintain 100% height and 90.6% stress after 10,000 cycles at 50% compression strain. It even can withstand a high compression strain of 90% for 1000 cycles with negligible structure deformation. The unique structure, outstanding mechanical performance, and highly sensitive current response enable the carbon aerogel to accurately detect human biosignals.

Carbon aerogels with excellent compressibility and resilience are attracting considerable attention in broad application prospects for their reversible resilience and resistance to damage from external stress. It is of great interest to explore green and low-cost carbon aerogels from sustainable resources but remains challenging because of the brittleness of carbon blocks. Herein, inspired by the anisotropic architectures in nature, we propose a bottom-up approach for fabricating an anisotropic carbon aerogel with a 3D lamellar structure from cellulose nanofibers. The aligned and continuous lamellar texture with desirable thickness (142 nm) can effectively transfer stress throughout the 3D network and resist the destruction at high compression, and thus, the carbon aerogel exhibits shape recovery from high compression strain and excellent fatigue resistance. The carbon aerogel can withstand extremely high compression strain (95%) for at least 50 cycles or 50,000 cycles at 50% strain with 84% height retention. Moreover, the excellent mechanical performance, stable 3D lamellar architecture, and high conductivity endow the carbon aerogel with rapid current response and high sensitivity in a wide pressure range (0.002–7 kPa). This study introduces the carbon aerogel as an excellent choice for fabricating the 3D tactile sensor to capture various signals of human motions.