Transparent, super stretchable, freezing-tolerant, self-healing ionic conductive cellulose based eutectogel for multi-functional sensors

In this study, we propose a non - toxic and low-cost fabrication of cellulose-based eutectogel through the ZnCl2/H2O/H3PO4 deep eutectic solvent (DES) to dissolve cellulose followed by free-radical polymerization of acrylamide. Particularly, the introduction of cellulose enhances the mechanical properties of eutectogels while eliminating the environmental concerns of the traditional nanocellulose fabrication process. Owing to the dynamic transfer of ions in the eutectogel network, the prepared eutectogels exhibit adjustable conductivity (0.9- 1.37 Sm-1, 15 °C) and stretching sensitivity (Gauge factor = 5.4). The resulting DES - cellulose-based eutectogels (DCEs) exhibited ultra stretchability (4086 %), high toughness (261.3 MJ/m3), excellent ionic conductivity (1.64 Sm-1, 20 °C), high transparency (>85 %), outstanding antifreezing performance (<-80 °C), and other comprehensive characteristics. The DCEs had been proven to have multiple sensitivities to external stimuli, like temperature, strain, and pressure. As a result, the DCEs can be assembled into multifunctional sensors. Moreover, this work also demonstrated the satisfactory performance of DCEs in flexible electroluminescent devices. The low cost and high efficiency made the preparation method of this experiment an efficient strategy for developing high-performance cellulose-based eutectogels, which would greatly promote the application of such materials in areas such as artificial skin for soft robots and other wearable devices.

Multi-material 3D printed eutectogel microneedle patches integrated with fast customization and tunable drug delivery

Microneedle patches are emerging multifunctional platforms for transdermal diagnostics and drug delivery. However, it still remains challenging to develop smart microneedles integrated with customization, sensing, detection and drug delivery by 3D printing strategy. Here, we present an innovative but facile strategy to rationally design and fabricate multifunctional eutectogel microneedle (EMN) patches via multi-material 3D printing. Polymerizable deep eutectic solvents (PDES) were selected as printing inks for rapid one-step fabrication of 3D printing functional EMN patches due to fast photopolymerization rate and ultrahigh drug solubility. Moreover, stretchable EMN patches incorporating rigid needles and flexible backing layers were easily realized by changing PDES compositions of multi-material 3D printing. Meanwhile, we developed multifunctional smart multi-material EMN patches capable of performing wireless monitoring of body movements, painless colorimetric glucose detection, and controlled transdermal drug delivery. Thus, such multi-material EMN system could provide an effective platform for the painless diagnosis, detection, and therapy of a variety of diseases.

Cellulose-reinforced highly stretchable and adhesive eutectogels as efficient sensors

A cellulose-reinforced eutectogel was constructed by deep eutectic solvent (DES) and cotton linter cellulose. Cellulose was dispersed in the ternary DES consisting of acrylic acid, choline chloride and AlCl3·6H2O. The photoinitiator was then introduced into the system to in situ polymerize acrylic acid monomer to form transparent and ionic conductive eutectogels while keeping all the DES. The crosslinks formed by Al3+ induced ionic bonds and reversible links formed by hydrogen bonds give the eutectogels high stretchability (3200 ± 200 % tensile strain), self-adhesive (52.1 kPa to glass), self-healing and good mechanical strength (670 kPa). The eutectogels were assembled into sensors and epidermal patch electrodes that demonstrated high quality human motion sensing and physiological signal detection (electrocardiogram and electromyography). This work provides a facile way to design flexible electronics for sensing.

Tunable durian seed gum-derived eutectogel as a novel coating material: Rheological, thermal, textural and barrier properties for enhanced food preservation

As a promising green and sustainable coating material, gum was extracted from durian seed to produce eutectogel, which the properties were tunable using natural deep eutectic solvent (NADES). Ten different eutectogels were successfully synthesized using durian seed gum (DSG) and xanthan gum (XG) gelators at different composition (5, 10, 15 %) to gel choline chloride-glucose (1:1), choline chloride-fructose (1:2) and betaine-glucose-water (1:1:1) NADESs. Results revealed that eutectogel was non-Newtonian and weak gel material with excellent thermostability up to 200 °C. When the gum content increased, the resulted eutectogel showed higher viscosity, yield stress, hardness, gumminess, adhesiveness, and weight holding capacity. In overall, choline chloride-fructose (1:2) NADES and 10 % of DSG formed an excellent eutectogel which remained stable and compatible upon 12 weeks of storage. It displayed superior viscoelastic, texture, gases and moisture barrier properties which were beneficial for food coating application. This eutectogel was able to extend the shelf life of fresh-cut apples during storage with lower weight loss and higher total phenolic content (TPC). The potential future of this well-characterized tunable DSG-derived eutectogel includes, but not limited to, food and pharmaceutical industries, smart sensing, flexible wearable electronics, water purification, supercapacitors and batteries.

Hydrophobic deep eutectic solvent-based eutectogels for underwater sensing

Eutectogels derived from deep eutectic solvents (DESs) exhibit great potential for the fabrication of flexible sensors. However, the hygroscopicity of eutectogels hinders their applications in underwater sensing. In this work, a hydrophobic eutectogel with exceptional long-term underwater stability is produced through one-step polymerization of lauryl methacrylate and glycidyl methacrylate in a hydrophobic DES. The hydrophobic gel network and hydrophobic DES fulfill the eutectogel with outstanding water resistance (water contact angle > 110°) and excellent mechanical properties in an aqueous environment, thus leading to extraordinary durability (over 1000 testing cycles). Additionally, based on this eutectogel, underwater strain and pressure sensors with high sensitivity, rapid responsiveness, and superior durability were fabricated for accurate real-time monitoring of human activity. Furthermore, it has been demonstrated that the eutectogel sensor can transmit information through Morse code, performing as a wearable underwater communicator. This research provides an exemplary way for a demonstration method of hydrophobic eutectogel for durable underwater applications.

Synthesis of a magnetic micro-eutectogel based on a deep eutectic solvent gel immobilized in calcium alginate: Application for green analysis of melamine in milk and dairy products

A new three-component magnetic eutectogel composed of a crosslinked copolymeric deep eutectic solvent (DES) and polyvinylpyrrolidone-coated Fe₃O₄ nano-powder impregnated in calcium alginate gel was synthesized and applied as a sorbent material in a green alternative micro solid-phase extraction of melamine in milk and dairy products. The analyses were performed using the HPLC-UV technique. The copolymeric DES was prepared through thermally-induced free-radical polymerization of [2-hydroxyethyl methacrylate]:[thymol] DES (1:1 mol ratio) as functional monomer, azobisisobutyronitrile (as initiator), and ethylene glycol dimethacrylate (as crosslinker). The sorbent was characterized using ATR-FTIR, ¹H & ¹³C FT-NMR, SEM, VSM, and BET techniques. The stability of the eutectogel in water and its effect on the pH of the aqueous solution was studied. A one-at-a-time approach was applied to optimize the impact of significant factors influencing sample preparation efficiency (sorbent mass, desorption conditions, adsorption time, pH, and ionic strength). The method validation was performed by evaluating matrix-matched calibration linearity (2-300 μg kg^-1, r² = 0.9902), precision, system suitability, specificity, enrichment factor, and matrix effect. The obtained limit of quantification (0.38 μg kg^-1) was lower than the established maximum level for melamine by Food and Drug Administration (FDA) (0.25 mg kg^-1), Food and Agriculture Organization (FAO) (0.5 & 2.5 mg kg^-1), and The European Union (EU) (2.5 mg kg^-1) in milk and dairy products. The optimized procedure was applied for the analysis of melamine in bovine milk, yogurt, cream, cheese, and ice cream. The obtained normalized recoveries of 77.4-105.3% (RSD% <7.0%) were acceptable regarding the practical default range set by the European Commission (70-120%, RSD≤20%). The sustainability and green aspects of the procedure were evaluated by the Analytical Greenness Metric Approach (0.6/1.0) and the Analytical Eco-Scale tool (73/100). This paper presents the first-time synthesis and application of this micro-eutectogel for the analysis of melamine in milk and milk-based dairy products.

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

In recent years, gel-based ion conductor has been widely considered in wearable electronics because of the favorable flexibility and conductivity. However, it is of vital importance, yet rather challenging to adapt the gel for underwater and dry conditions. Herein, an anti-swelling and anti-drying, intrinsic conductor eutectogel is designed via a one-step radical polymerization of acrylic acid and 2, 2, 2‑trifluoroethyl methacrylate in binary deep eutectic solvents (DESs) medium. On the one hand, the synergistic effects of hydrophilic/hydrophobic heteronetworks can elicit the integrity stability of eutectogel in liquid environment. It is proved that both the mechanical property and conductivity are maintained after immersing in different salt, alkaline and acid solution and organic solvent for one month. On the other hand, the eutectogel inherits well conductivity (93 mS/m), anti-drying and antibacterial properties from DESs. Based on the above features, the resulting eutectogel can be assembled as smart sensor for stable information transmission in air and underwater with fast response time (1 s), high sensitivity (Gauge factor = 1.991) and long-time reproducibility (500 cycles, 70 % strain). Considering the simple preparation and integration of multiple functions, the binary cooperative complementary principle can provide insights into the development of next-generation conductive soft materials.