A Directional Strain Sensor Based on Anisotropic Microhoneycomb Cellulose Nanofiber‐Carbon Nanotube Hybrid Aerogels Prepared by Unidirectional Freeze Drying

Abstract

Aerogels are generally used as the reinforcements for composites due to their stable self-supporting networks, good continuity, and abundant porosity. [1][2][3][4][5][6][7] Unlike traditional nanoparticle fillers, aerogel fillers enable better control of the distribution of the reinforcement in the matrix material, e.g., polymers. [8][9][10][11][12] Aerogels can be prepared by chemical vapor deposition, hydrothermal methods, freeze drying, and other approaches. [1,[13][14][15] These aerogels have demonstrated impressive reinforcement of polymer matrixes. [1,3] However, most aerogels are isotropic, which prevents their composites from being used in areas, such Aerogels are one of the most popular composite reinforcement materials because of their high porosity and their continuous and homogeneous network. Most aerogels are isotropic, thus leading to isotropic composites when they are used as fillers. This fundamentally limits their applications in areas where anisotropy is needed. Here, an anisotropic microhoneycomb cellulose nanofiber-(CellF)-carbon nanotube (CNT) aerogel (denoted MCCA) is reported that contains unidirectionally aligned penetrating microchannels, which is prepared by a unidirectional freeze-drying method, using the structure-directing function of the CellFs. Due to its anisotropic nature, MCCAreinforced polydimethylsilexane (denoted MCCA/PDMS) shows distinct anisotropic behavior, with the electrical conductivity and Young's modulus along the direction of penetrating microchannels being approximately twice those in the orthogonal direction. MCCA/PDMS is used to make "directional" strain sensors with electrical resistance as the output signal. They demonstrate a 92% sensitivity difference between the microchannel direction and its orthogonal direction. This approach can be used to prepare anisotropic MCCA-based composites with other polymers for different applications. SensorsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

1D/2D Nanomaterials Synergistic, Compressible, and Response Rapidly 3D Graphene Aerogel for Piezoresistive Sensor

“…Aerogels are lightweight porous solid materials characterized by their extremely low density, high porosity, and high specific surface area. [ 1,2 ] In general, aerogels can be prepared by chemical vapor deposition (CVD), [ 3 ] hydrothermal methods, [ 4 ] and 3D printing, [ 5 ] while they can be prepared form silica, [ 6 ] carbon nanotubes, [ 7 ] graphene, [ 8,9 ] polyimide, [ 10,11 ] Kevlar, [ 12,13 ] and natural materials [ 14–16 ] to name a few. Due to the unique structure and properties of aerogels, they can be utilized for energy storage and conversion, [ 17–19 ] sensors, [ 20,21 ] catalyst support, [ 22,23 ] environmental remediation, [ 24,25 ] and many other diverse applications.…”

pH‐Dependent Morphology Control of Cellulose Nanofiber/Graphene Oxide Cryogels

“…[ 41 ] We have further extended the structural directing functionalities of TOCNs and revealed potential applications, such as sodium ion batteries [ 42 ] and strain sensors. [ 43 ]…”

Ultra‐High Surface Area Nitrogen‐Doped Carbon Aerogels Derived From a Schiff‐Base Porous Organic Polymer Aerogel for CO2 Storage and Supercapacitors

“…Over the last two decades, porous carbon aerogels have been actively studied for CO 2 capture as well as for supercapacitors because of their unique structural features such as large surface area, low density, high electrical conductivity, and stable physicochemical properties . To realize a large surface area of carbon aerogels, however, special processes such as activation, templating, freeze‐drying, and supercritical drying are usually involved . Meanwhile, most carbon aerogels obtained exhibit CO 2 uptake capacities which are well below 3–4 mmol g −1 adsorbent at ambient pressure, the value that represents the minimum working capacity necessary to compete with the liquid‐phase amine system .…”