Ultrasensitive Mg²⁺-Modulated Carbon Nanotube/Tannic Acid Aerogels for High-Performance Wearable Pressure Sensors

Abstract

Three-dimensional (3D) carbon nanotube-based porous networks have received considerable attention as active nanomaterials for flexible/wearable sensor applications due to their excellent conductivity and mechanical flexibility. Herein, ultralight, biocompatible, and conductive SWCNT/tannic acid (TA) and Mg 2+ /SWCNT/TA aerogels have been facilely fabricated using TA as a dispersion reagent and crosslinker and Mg 2+ to introduce a metal−phenolic network. The construction of a SWCNT@ TA core−shell structure and the low CNT concentration of SWCNT/TA 3:3 contribute to a high linear sensitivity of 432 kPa −1 in a wide pressure range (0.014−28 kPa), while Mg 2+ modulation endows Mg 2+ /SWCNT/TA 1:1 with an ultrahigh linear sensitivity of 13662 kPa −1 in a pressure range of 0.014−1.05 kPa. The superior sensing performance of as-prepared aerogels, including high sensitivity, wide working range, low detection limit (14 Pa), and fast stimuli-response (200−300 ms), enables them to detect tiny changes in human biosignals and imperceptible vibration, which show great potential in applications of health monitoring, human− machine interfaces, and various flexible electronics.

Whey Protein Isolate-Based Aerogels with Improved Hydration Properties for Food Packaging Applications

“…The band at 1396 cm –1 can be assigned to C–N stretching and symmetric −CH 3 bending. , Most of the characteristic bands of the tannins appear in the same range as the characteristic bands of the WPI, and therefore, they could not be distinguished. However, the two peaks at 1171 and 1034 cm –1 , attributed to the asymmetric and the symmetric C–O–C stretching in Fintan C, are also present in the spectra of all aerogels prepared from Fintan C, confirming the presence of the tannin in the aerogel matrix . For all hydrophobized samples, two extra bands could be observed associated with the Si–(CH 3 ) 3 groups; one at 1250 cm –1 , due to CH 3 symmetric deformation, and another one at 845 cm –1 , due to CH 3 rocking and Si–C stretching …”

“…However, the two peaks at 1171 and 1034 cm −1 , attributed to the asymmetric and the symmetric C−O− C stretching in Fintan C, are also present in the spectra of all aerogels prepared from Fintan C, confirming the presence of the tannin in the aerogel matrix. 36 For all hydrophobized samples, two extra bands could be observed associated with the Si−(CH 3 ) 3 groups; one at 1250 cm −1 , due to CH 3 symmetric deformation, and another one at 845 cm −1 , due to CH 3 rocking and Si−C stretching. 49 The 13 C CPMAS NMR spectra (Figures 2 (bottom) and S2) showed all of the peaks expected for the protein chain carbons.…”

“…Tannins (and tannic acid) have been used for aerogel synthesis in various cases: (a) for the enhancement of the mechanical properties of aerogels, e.g., silica 33 or poly(vinyl alcohol) 34 aerogels, (b) for preparing precursors for silicon carbide 33 or carbon 35 aerogels, and (c) for preparing aerogel sensors with a good sensing performance. 36 The main objective of this work, improving the stability of WPI-based aerogels in aqueous environments, was accomplished by tannin-assisted phase separation and gelation, drying with supercritical CO 2 and followed by gas-phase silanization of the resulting aerogels. Tannins were chosen for reducing the hydrophilicity of WPI aerogels, via a process mimicking leather tanning, 37 the most important chemical process that converts animal skin into leather by stabilizing the collagen fibers.…”

“…Tannins are classified either as hydrolyzable and yield gallic or ellagic acid after hydrolysis (Figure c), or as condensed that contain flavanol moieties (Figure c), which in turn form oligomeric or polymeric structures (condensed tannins do not contain sugar residues). Tannins (and tannic acid) have been used for aerogel synthesis in various cases: (a) for the enhancement of the mechanical properties of aerogels, e.g., silica or poly­(vinyl alcohol) aerogels, (b) for preparing precursors for silicon carbide or carbon aerogels, and (c) for preparing aerogel sensors with a good sensing performance …”

Recyclable Ionic Conductive Hydrogels Based on Autonomous Polymerization of α-Lipoic Acid for Flexible Wearable Electronic Sensors

“…In recent years, with the development of the Internet of Things, the connection between electronic sensing equipment and physical substances has become more and more important. Flexible wearable electronic sensors have attracted much attention because they can detect human motion and physiological signals conveniently. − Traditional flexible wearable electronic sensing devices usually combine conductive materials with flexible substrates that are adhered to the human surface through external effects to detect human motion and physiological signals. However, the traditional wearable electronic sensing devices are usually rigid and fragile and are unable to withstand large tensile deformation which could lead to the adaptability to human skin, and the long-term conducive stability of the sensing device is poor.…”