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...

Compressible and elastic carbon aerogels (CECAs) hold great promise for applications in wearable electronics and electronic skins. MXenes, as new two-dimensional materials with extraordinary properties, are promising materials for piezoresistive sensors. However, the lack of sufficient interaction among MXene nanosheets makes it difficult to employ them to fabricate CECAs. Herein, a lightweight CECA is fabricated by using bacterial cellulose fiber as a nanobinder to connect MXene (Ti3C2) nanosheets into continuous and wave-shaped lamellae. The lamellae are highly flexible and elastic, and the oriented alignment of these lamellae results in a CECA with super compressibility and elasticity. Its ultrahigh structural stability can withstand an extremely high strain of 99% for more than 100 cycles and long-term compression at 50% strain for at least 100 000 cycles. Furthermore, it has a high sensitivity that demonstrates not only an ultrahigh linearity but also a broad working pressure range (0–10 kPa). In particular, the CECA has a high linear sensitivity in almost the entire workable strain range (0–95%). In addition, it has very low detection limits for tiny strain and pressure. These features enable the CECA-based sensor to be a flexible wearable device to monitor both subtle and large biosignals of the human body.

A compressible carbon aerogel with not only super mechanical performances but also ultrahigh linear sensitivity is fabricated from MXene nanosheets and cellulose nanocrystals (CNCs).

A mechanically strong, sensitive and lightweight CNT/rGO–CNF carbon aerogel is fabricated by synergistic assembly of CNFs and CNTs to form ordered wave-shaped rGO layers and reinforcing the carbon layers.