Ultrastretchable Composite Organohydrogels with Dual Cross-Links Enabling Multimodal Sensing

Abstract

Building multiple cross-links or networks is a favorable way of diversifying applications of the hydrogels, which is also available for the organohydrogels prepared via the solvent replacement way. However, the situations become more complicated for organohydrogels due to the presence of replaced solvents. Therefore, the correlations between the multiple cross-links and final performance need to be better understood for the organohydrogels, which is vital for tailoring their inherent properties to expand final application scenarios. Polyacrylamide (PAM)/poly(vinyl alcohol) (PVA)/MXene composite organohydrogels with dual cross-links, namely, the covalently cross-linked PAM chains as the primary network and the physically cross-linked PVA/PAM chains with MXene particles as the secondary cross-links, were developed here for the study. The occurrence of the secondary cross-links plays multiple roles as sacrificial units endowing the system with ultrastretchability with an excellent strain–resistance effect and as temperature-sensitive units endowing the system with thermosensation ability with an outstanding temperature coefficient of resistance. Thus, the optimized sample can be used as a strain sensor with excellent environmental tolerance for detecting human motion as a pressure sensor to probe compression with weak deformation and as a thermal sensor to capture environmental temperature changes. This work provides valuable information on developing organohydrogels with superior performance for multimodal sensors.

Crosslinking of Bacterial Cellulose toward Fabricating Ultrastretchable Hydrogels for Multiple Sensing with High Sensitivity

“…The current ionic conductive hydrogels were fabricated via a facile strategy of insitu polymerization similar to the previous study. 18 First, 10 g BC dispersions with various concentrations (0−0.47%) were sonicated for 30 min to ensure homogenization for the nanofibers. Second, 5 g AM monomer, 0.04 g APS initiator, 0.003 g MBA cross-linker, and 2 g water were added into the BC dispersion and homogenized to form the precursor solution.…”

MXene‐Based Flexible Sensors: Materials, Preparation, and Applications

“…However, simple hydrogels as substrate materials still have some flaws. For starters, hydrogels' mechanical properties are poor; how to effectively improve the mechanical strength of hydrogel structures is still a research priority; at the moment, the most commonly used methods are double network molecular cross‐linking, [ 87 ] fiber reinforced modification, [ 88 ] particle reinforced modification, [ 72 ] and so on. Luan et al.…”

“…However, simple hydrogels as substrate materials still have some flaws. For starters, hydrogels' mechanical properties are poor; how to effectively improve the mechanical strength of hydrogel structures is still a research priority; at the moment, the most commonly used methods are double network molecular cross-linking, [87] fiber reinforced modification, [88] particle reinforced modification, [72] and so on. Luan et al [83] combined conductive MXene nanosheets with a polyacrylamide (PAM) and sodium alginate (SA) dual network hydrogels (Figure 5c,d), and the resulting MXene-based composite hydrogel has good mechanical properties (tensile properties up to 2000%), excellent stability, and sensitive sensing properties, with potential applications in human-computer interaction and health monitoring.…”

MXene‐based dual‐network conductive organic hydrogel for wearable sensor to monitor human motions

“…[1][2][3] At the same time, conductive hydrogels can be used to create flexible wearable strain sensors because of their superior electronic properties, excellent mechanical capabilities, and exceptional biological properties. [4][5][6] However, conductive hydrogels using pure water as the medium freeze at below-freezing temperatures, resulting in loss of their elasticity and conductivity and limiting their practical applications, such as flexible strain sensors. In addition to losing moisture at room temperature, these hydrogels are also less durable and stable over time.…”

“…Conductive hydrogels have received more and more attention, especially their dual network structure has also attracted the attention of many scholars 1–3 . At the same time, conductive hydrogels can be used to create flexible wearable strain sensors because of their superior electronic properties, excellent mechanical capabilities, and exceptional biological properties 4–6 . However, conductive hydrogels using pure water as the medium freeze at below‐freezing temperatures, resulting in loss of their elasticity and conductivity and limiting their practical applications, such as flexible strain sensors.…”