Extreme-environment-adapted eutectogel mediated by heterostructure for epidermic sensor and underwater communication

One-step Fabrication of Physical Eutectogel with Recyclability: Crystalline Domain Regulation Induced by Microgels

HYPOTHESIS

Despite their non-volatility, low cost, and recyclability, physical eutectogels' appeal is hindered by the intricate fabrication process and the involvement of hazardous chemicals. The network of polyvinyl alcohol (PVA) in deep eutectic solvent (choline chloride and glycerol) might be developed by the addition of microgels of polyacrylic acid (Carbopol).

EXPERIMENTS

Hydrogen-bond interactions between Carbopol and PVA are revealed through Fourier-transform infrared spectroscopy. The impact of microgels on crystalline domains and the polymer network can be observed using X-ray diffraction and scanning electron microscopy. The physical properties of the eutectogel, including mechanical strength and ionic conductivity, are investigated as well. Finally, the strain-sensing ability and remarkable recyclability of the eutectogel are demonstrated.

FINDINGS

The physical eutectogel can be obtained through a one-step fabrication process using only green and low-cost materials. It demonstrates robust strength (1.02 MPa) and remarkable stretchability (1000 % strain). This is attributed to the uniform dispersion of PVA crystalline domains within the deep eutectic solvent, facilitated by the hydrogen bonds and space restriction effects between PVA and Carbopol. Furthermore, the physical eutectogel with recyclability can consistently generate electrical resistance signals, highlighting its potential as a reliable strain sensor.

Ultra-Tough and Highly Stretchable Dual-Crosslinked Eutectogel Based on Coordinated and Non-Coordinated Two Types Deep Eutectic Solvent Mixture

Eutectogels are gaining attention in flexible device applications for their superior ionic conductivity, stability, biocompatibility, and cost-effectiveness. However, most existing eutectogels suffer from low strength and toughness. Herein, ultra-tough and highly stretchable polyacrylamide (PAM) eutectogels featuring a dual-crosslinked network comprising chemical cross-linking and physical cross-linking facilitated by metal coordination bonds and hydrogen bonds are developed. This is achieved through a controlled strategy involving polymerization of acrylamide in a coordinated metal salt-type deep eutectic solvent (DES) combined with a non-coordinated choline chloride (ChCl)-type DES mixture. By varying the molar ratio of these two types of DES, exceptional and adjustable mechanical properties of the resulting eutectogel are achieved, including a high tensile strength ranging from 2.9 to 8.2 MPa and elongation at break ranging from 1725 to 747%, at a 70 wt% DES content. Furthermore, the reversible non-covalent crosslinking in these eutectogels enables self-recovery and self-healing capabilities of eutectogels. The prepared eutectogels also exhibit outstanding ionic conductivity (3.56 mS cm-1 ), making them well-suited for use as strain sensors in human motion detection. The toughening strategy is universally effective for creating tough eutectogels using coordinated metal salt-type DES with various metal ions, as well as a diverse range of coordinatable polymers.

Green, recyclable, mechanically robust, wet-adhesive and ionically conductive cellulose-based bioplastics enabled by supramolecular covalent hydrophobic eutectic networks

The development of novel cellulose-based bioplastics (CBPs) is highly desirable because CBPs are green, rationally use resources, and lead to a reduction in environmental pollution compared to alternative materials. However, incorporating high transparency, water resistance, mechanical robustness, wet-adhesion, ionic conductivity and recyclability into CBP remains a challenge. In this paper, novel CBPs with supramolecular covalent networks are fabricated by introducing polymerizable hydrophobic deep eutectic solvents (HDES) into ethylcellulose (EC) networks through in situ plasticization followed by a rapid photopolymerization process. The excellent molecular interfacial compatibility enables EC to be loaded with a high content of poly(HDES), while allowing high transparency (more than 90 %) of the prepared CBPs. Multiple intermolecular interactions provide CBPs with mechanical robustness, water resistance, and underwater adhesion, and CBPs can be readily recovered by the solvent in a closed loop. Moreover, CBPs possess inherent ionic conductivities, and using them as green substrates, personalized electroluminescent devices can be successfully constructed. The method proposed in this paper provides a new strategy for the preparation of multifunctional CBPs, which will greatly enrich their applications in self-adhesive materials, green flexible electronics and other package materials.

Simple and Rapid Way to a Multifunctionally Conductive Hydrogel for Wearable Strain Sensors

Conductive hydrogels have gained increasing attention in the field of wearable smart devices. However, it remains a big challenge to develop a multifunctionally conductive hydrogel in a rapid and facile way. Herein, a conductive tannic acid-iron/poly (acrylic acid) hydrogel was synthesized within 30 s at ambient temperature by the tannic acid-iron (TA@Fe3+)-mediated dynamic catalytic system. The TA@Fe3+ dynamic redox autocatalytic pair could efficiently activate the ammonium persulfate to initiate the free-radical polymerization, allowing the gelation to occur easily and rapidly. The resulting hydrogel exhibited enhanced stretchability (3560%), conductivity (33.58 S/m), and strain sensitivity (gauge factor = 2.11). When damaged, it could be self-healed through the dynamic and reversible coordination bonds between the Fe3+ and COO- groups in the hydrogel network. Interestingly, the resulting hydrogel could act as a strain sensor to monitor various human motions including the huge movement of deformations (knuckle, wrist) and subtle motions (smiling, breathing) in real time due to its enhanced self-adhesion, good conductivity, and improved strain sensitivity. Also, the obtained hydrogel exhibited efficient electromagnetic interference (EMI) shielding performance with an EMI shielding effectiveness value of 24.5 dB in the X-band (8.2-12.4 GHz). Additionally, it displayed antibacterial properties, with the help of the activity of TA.