【DT New Materials】It is learned that hydrogel is a three-dimensional network structure containing a large amount of water, which is ubiquitous in biological systems, and the hydrogel system based on a variety of materials has been continuously developed, based on its unique properties such as flexibility and biocompatibility, and has been widely studied and applied in many fields such as electrical devices, sensors and biomedicine.
This paper reviews and organizes 10 representative hydrogel-related work recently published in top international journals such as Science and Nature.
"An Integrally Formed Janus Hydrogel for Robust Wet-tissue Adhesive and Anti-postoperative Adhesion"
DOI: 10.1002/adma.202300394
Recently, the research group of Professor Liu Zhenzhen of the Institute of Physical Engineering of South China Agricultural University proposed a general strategy for the rapid construction of Janus hydrogels with asymmetric adhesion, and prepared MAH hydrogels with asymmetrical adhesion for the first time by one-step method by regulating the self-assembly behavior of emulsion droplets inside the hydrogel and the distribution of upper and lower surfaces. The experimental results show that at a low speed of 600rpm, larger emulsion droplets composed of hydrophobic monomers and surfactants are mainly distributed on the upper surface of the hydrogel, which promotes the enrichment of more -COOH groups on the lower surface, forming an asymmetric structure of hydrophilic surface on the upper surface of hydrophobic. Under the joint influence of physical/chemical action, the lower surface of the hydrogel achieves high strength and rapid adhesion to the wet tissue surface, and the difference in tissue adhesion strength on the upper and lower surface of the hydrogel is as high as 20. The results of rabbit gastric perforation repair experiment proved that.
2. "Toughening Double Network Hydrogels by Polyelectrolytes"
DOI: 10.1002/adma.202301551
Recently, the research group of Cheng Yilong of Xi'an Jiaotong University made the first discovery. Compared with polyacrylic acid (PAA), the introduction of sodium anionic polyacrylate (P(iAA)) in polyvinyl alcohol (PVA) hydrogels can significantly improve the mechanical properties of hydrogels. The tensile strength, compressive strength, Young's modulus, toughness and fracture energy of PVA10/P(iAA)15 hydrogels were 73 times, 64 times, 28 times, 135 times and 19 times higher than PVA10/PAA15 hydrogels, respectively.
The mechanism of enhancement of the Hofmeister effect of polyelectrolytes on the mechanical properties of hydrogels was elucidated experimentally: compared to PAA, which may interfere with the formation of hydrogen bonds between PVA chains.
3. "A polymeric hydrogel electrocatalyst for direct water oxidation"
DOI: 10.1038/s41467-023-36532-x
Recently, Dr. Pei Zengxia and Dr. Shenlong Zhao of the University of Sydney collaborated with Professor Chen Zhongfang of the University of Puerto Rico to report that a class of polymer sodium polyacrylate (PANa) hydrogels can be directly used as OER electrocatalysts. The authors combined theoretical calculations, electrochemical testing, in situ spectral characterization, and isotope labeling comparisons to confirm and for the first time observe spectroscopic evidence of key superoxide intermediates in OER for metal-free electrocatalysts.
The optimized PANa-based electrocatalyst exhibits excellent OER catalytic performance in alkaline electrolyte, with an apparent 10mAcm-2OER current overpotential as low as 316mV and a Tafel slope of only 42mV dec−1, which is comparable to the benchmark IrO2 catalyst. Its intrinsic conversion frequency at 350mV overpotential reaches 1.65×10-2 s-1, which is also the same order of magnitude as commercial IrO2 (5.18×10-2 s-1). In addition, these gel-based composite electrodes are simple to prepare (no pyrolysis required), processable, inexpensive, and OER on different substrates and at different pH environments. Given the rich and manageable chemical structure of the hydrogel skeleton, this research is promising.
4. "A self-healing electrically conductive organogel composite"
https://www.nature.com/articles/s41928-023-00932-0
Professor Carmel Majidi from Carnegie Mellon University has prepared a self-healing conductive organogel composite. It has a high conductivity of 7×104 S·m-1, fast and efficient self-healing ability, and ideal mechanical properties. In addition, by using ethylene glycol (EG) instead of water as a solvent, this organic gel is given its resistance to drying. The conductive organogel is expected to be used in reconfigurable flexible circuits and reconfigurable bioelectrodes for electromyography (EMG) sensing.
Its organogel composites based on polyvinyl alcohol-sodium borate are expected to be used for their high electrical conductivity, low stiffness, high tensile properties, and self-healing ability of mechanical and electrical properties.
5."A Facile and Versatile Approach to Construct Photoactivated Peptide Hydrogels by Regulating Electrostatic Repulsion"
DOI: 10.1021/acsnano.2c10896
Recently, Professor Bao Chunyan's research group from the School of Chemistry and Molecular Engineering of East China University of Science and Technology proposed a simple and general strategy to construct photoactivated peptide hydrogels by adjusting electrostatic repulsion to achieve precise control of the shape and mechanical properties of peptide supramolecular hydrogels, and further applied them to artificial extracellular matrices (ECMs) to achieve two-dimensional/three-dimensional cell culture and behavioral regulation.
At the heart of this peptide gel strategy is the design of one that links them by 2-nitrobenzyl photolysis groups. The presence of charge repulsion makes it difficult for peptide molecules to assemble into an ordered structure in aqueous solution and present a solution state. After the application of ultraviolet light, the charge repulsion part is removed with the cleavage of photoresponsive molecules, which then triggers the assembly of the generated gel factors and the formation of supramolecular hydrogels, and the rapid sol-gel conversion makes the formation and mechanical properties of the hydrogels spatiotemporal and spatial controllable.
This article reports one. Before illumination, peptide molecules show good solubility due to the presence of intermolecular charge repulsion; After illumination, the removal of charge repulsion activates the aggregation and assembly of peptide gel factors, and its high aggregation tendency promotes the rapid formation of hydrogels, thereby realizing the space-time controllable construction of light. The spatial controllability of light enables precise programming of hydrogel shapes and localization of cell growth, and time controllability of light enables the regulation of hydrogel mechanical strength and mediates the corresponding cell behavior.
6."Wide Humidity Range Applicable, Anti-Freezing and Healable Zwitterionic Hydrogels for Ion-Leakage-Free Iontronic Sensors"
DOI: 10.1002/adma.202211617
Meng Hong's research group at Peking University Shenzhen Graduate School studied the addition of a green solvent, acetone glycerol (solketal), to the inner salt DMAPS hydrogel, and in a wide humidity range, solketal hydrogel is superior to the most commonly used solvent - glycerol.
In addition, thanks to the presence of solketal, one can be introduced to further alter the properties of the hydrogel. The resulting hydrogel achieves a fracture strain of about 2000% in the range of humidity to 90%RH and temperature of -20 to 40°C, and has good self-healing properties.
Using the zwitterionic groups in the hydrogel and the stable water content, the optimized hydrogel was used as a dielectric layer to construct an ionic pressure sensor. Achieved no leakage ions, high sensitivity (> 1100 kPa-1), wide humidity and temperature suitability. By combining a hydrogel substrate with a Ag@poly (DMAPS) slurry, a wide humidity healable and stretchable electrode is obtained. Combining high-performance electrodes and dielectric layers, one was developed.
7. "Infected Diabetic Wound Regeneration Using Peptide-Modified Chiral Dressing to Target Revascularization"
DOI: 10.1073/pnas.1612277113
Professor Feng Chuanliang/Associate Professor Dou Xiaoqiu, School of Materials Science and Engineering, Shanghai Jiao Tong University, Professor Fang Yong of Shanghai Jiao Tong University School of Medicine, and researcher Peng Yinbo of the Department of Burns, Ninth People's Hospital of Shanghai Jiao Tong University, were inspired by the multiple chiral sites existing on AGEs, endowed wound dressings with rich chiral structural characteristics, and increased the in situ adsorption of AGEs to AGEs through the stereoselective interaction between AGEs and chiral sites on wound dressings.
This peptide-modified chiral gel dressing offers a promising treatment. Due to the importance of vascular regeneration in the treatment of diabetic complications, this chiral biomedical material may play a wide range of roles in the treatment of diabetic complications such as peripheral neuropathy and peripheral artery disease.
8. "Tough Hydrogel Electrolytes for Anti-Freezing Zinc-Ion Batteries"
DOI: 10.1002/adma.202211673
Professor He Ximin's research group at the University of California, Los Angeles successfully developed a hydrogel electrolyte by using the co-insoluble effect of polymer mixed solvent and the salting out effect of antifreeze salt solution.
Flexible waterborne batteries are considered ideal for future soft electronics due to their inherent safety and cost-effectiveness, but due to their limitations in temperature tolerance and shock resistance, these factors are essential to ensure stable battery operation. In this work, through joint utilization, a method for preparing hydrogel electrolytes with frost resistance, high mechanical stability, enhanced mass transport and inhibition of dendrites and side reactions was proposed. Quasi-solid-state antifreeze batteries made with this hydrogel electrolyte undergo more than 20,000 cycles at a rate of 2 A g-1 at -30,000 °C, have ultra-high capacity retention, and can withstand repeated hammer impacts or car crushing.
Following this strategy, this platform can be extended to other salts and processes to enable a wider range of types of battery systems. This work may broaden the application conditions of soft electronic devices and provide a novel approach for the next generation of flexible batteries.
9."Ferroelectricity in layered bismuth oxide down to 1 nanometer"
DOI: 10.1126/science.abm5134
Professor Zhang Linxing and Professor Tian Jianjun of University of Science and Technology Beijing and Professor Lu Yue of Beijing University of Technology designed a thin film with a layered structure of bismuth oxide, which can stabilize the ferroelectric state to 1 nm by samarium binding.
The bismuth oxide film designed in the study is a chemical solution. On this basis, a standard ferroelectric hysteresis loop line with a thickness of about 1 nm to 4.56 nm was observed during the implementation, and its residual polarization was quite large, from 17 to 50 μcoulombs per square centimeter. According to experiments, the theoretical calculation and analysis can be carried out using first-principles methods, and it is determined that the ferroelectric thin film material is an lone pair–driven ferroelectric material driven by an isolated electron pair.
10.“Hydrogel Nanoarchitectonics of a Flexible and Self-adhesive Electrode for Long-term Wireless Electroencephalogram Recording and High-accuracy Sustained Attention Evaluation”《 Multifunctional hydrogel sensing interface to achieve high-quality non-invasive acquisition of EEG signals"
DOI: 10.1002/adma.202209606
Recently, Prof. Shuo Bai, Prof. Xuehai Yan and Prof. Anhe Wang from the Institute of Process Engineering, Chinese Academy of Sciences, together with Associate Professor Xulin Zhang of Tsinghua University, proposed a strategy using a multifunctional hydrogel sensing interface to solve the problem of non-invasive acquisition of high-quality EEG signals. A hydrogel system with excellent conductivity, adhesion, flexibility, elasticity, biocompatibility and transparency was constructed through the multifunctional nanoparticle enhancement effect and homogeneous network effect, which was used to establish an efficient and stable sensing interface between human tissues and electrodes, so as to realize the direct collection of high-quality EEG signals from the human surface.
The multi-channel electrode based on this hydrogel is lightweight and portable, with the ability of online signal analysis, wireless signal transmission, and excellent stability. Furthermore, the algorithm converts the collected EEG signals into attention levels and can be subdivided into 7 levels from low to high, and the average prediction accuracy of each level can be achieved.
★ Platform Statement
Some of the materials originate from the Internet, and the copyright belongs to the original author. The purpose of sharing is only industry information transmission and exchange, and does not represent the position of this public account and confirm its authenticity. If you feel unwell, please contact us for timely treatment. Welcome to participate in the submission and sharing!