Qinhua Wang,Xiaofeng Pan,Changmei Lin,Dezhi Lin,Yonghao Ni,Lihui Chen,Liulian Huang,Shilin Cao,Xiaojuan Ma
Gel-based strain sensors have great potential in the fields of motion detection and real-time healthcare. Nevertheless, the relatively low strain sensitivity and inferior anti-freezing property limit the utilization of these sensors. In this work, a novel multifunctional organohydrogel sensor was developed based on a poly (acrylic acid) (PAA) skeleton with poly (3,4-ethylenedioxythiophene): sulfonated lignin (PEDOT:SL) as the conductive material and a water/glycerol binary solvent as the dispersion medium. The conductive, self-wrinkled, soft and elastic properties endue the organohydrogel sensor with a superior gauge factor (GF) of up to 7 (strain: 100%), while the freezing tolerance of the water/glycerol solvent endows the organohydrogel with an excellent anti-freezing property. The organohydrogel sensor senses not only the movement of limbs, but also a weak pulse and throat vibrations. Moreover, physiological signals such as those used for electrocardiography (ECG) and electromyography (EMG) can be readily detected. In addition, the cell culture test shows that the organohydrogel is nontoxic, and the animal experiments demonstrate that the organohydrogel can protect skin from frostbite. Overall, this work presents a new concept to use lignin for conductive PEDOT polymerization and integrates the fabrication of conductive organohydrogel materials for precise strain sensing.
Jianzhuang Shi,Ruoyu Dong,Changbin Ji,Wenxin Fan,Tengbo Yu,Yanzhi Xia,Kunyan Sui
Self-wrinkling hydrogels enable various engineering and biomedical applications. The major challenge is to couple the self-wrinkling technologies and enhancement strategies, so as to get rid of the poor mechanical properties of existing self-wrinkling gels. Herein we present a facile diffusion–complexation strategy for constructing strong and ultratough self-wrinkling polyelectrolyte hydrogels with programmable wrinkled structures and customizable 3D configurations. Driven by the diffusion of low-molecular-weight chitosan polycations into the polyanion hydrogels, the high-modulus polyelectrolyte complexation shells can form directly on the hydrogel surface. Meanwhile, the polyanion hydrogels deswell/shrink due to the low osmotic pressure, which applies an isotropous surface compressive stress for inducing the formation of polygonal wrinkled structures. When the diffusion–complexation reaction occurs on a pre-stretched hydrogel sheet, the long-range ordered wrinkled structures can form during the springback/recovery of the hydrogel matrix. Moreover, through controlling the regions of diffusion–complexation reaction on the pre-stretched hydrogels, they can be spontaneously transformed into various 3D configurations with ordered wrinkled structures. Notably, because of the introduction of plenty of electrostatic binding (i.e., sacrificial bonds), the as-prepared self-wrinkling gels possess outstanding mechanical properties, far superior to the reported ones. This diffusion–complexation strategy paves the way for the on-demand design of high-performance self-wrinkling hydrogels.
Electrochromic devices (ECDs) based on polyaniline (PANI) can alter their optical properties reversely by varying applied voltages, showing great potential in infrared (IR) information concealment. However, the traditional ECD with a flat PANI layer tends to perform unsatisfactorily in IR emissivity regulation and response time, resulting in risks of information leakage and low transfer efficiency. To address these challenges, a wrinkled microstructure is incorporated into the PANI layer (PANI-W) of the ECD (ECD-W) through a self-wrinkling method. Theoretic simulations combined with experimental results verify that the PANI-W endows an enhanced antireflection effect and a more complete redox degree. As a result, the ECD-W exhibits an exceptional IR emissivity modulation (0.375) and a short response time (1.8 s/2.6 s), allowing it to realize a temperature modulation of 8.9 °C. Moreover, various patterned and anti-patterned ECDs-W are feasibly prepared without masks, and more complicated patterns can be realized by erasing the unnecessary part of PANI-W on the ECDs-W. Two encryption/decryption strategies based on these ECDs-W are presented to provide more secure ways for IR information concealment. This research offers guidance to achieve high-performance ECDs with more effective spectrum regulation and faster responses, showing great potential in thermal regulation and IR information protection.
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