Youqiang Li

Bio: Youqiang Li is an academic researcher from Changchun University. The author has contributed to research in topics: Self-healing hydrogels & Gauge factor. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

A highly sensitive strain sensor based on a silica@polyaniline core–shell particle reinforced hydrogel with excellent flexibility, stretchability, toughness and conductivity

Abstract: Hydrogel-based flexible strain sensors for personal health monitoring and human-machine interaction have attracted wide interest among researchers. In this paper, hydrophobic association and nanocomposite conductive hydrogels were successfully prepared by introducing polyaniline coated silica (SiO2@PANI) core-shell particles into an acrylamide-lauryl methacrylate (P(AM/LMA)) copolymer matrix. The hydrophobic interaction between the SiO2@PANI core-shell particles and the hydrophobic LMA in the P(AM/LMA) chains induced the hydrogels with outstanding mechanical properties. Furthermore, the polyaniline on the SiO2 surface and the inorganic salt formed a conductive network, which synergistically enhanced the conductivity of the hydrogels. The obtained hydrogels integrate high tensile strength (1398 kPa), ultra-stretchability (>1000%), wonderful strain sensitivity (gauge factor = 10.407 at 100-1100% strain), quick response (300 ms), and excellent durability (>300 cycles) due to the hydrophobic association and nanocomposite effect. The prepared SiO2@PANI-P(AM/LMA) hydrogel shows high stress sensitivity to detect human movements and displays a broad application prospect in flexible strain-sensor field.

Carbon Nanotubes and Silica@polyaniline Core-Shell Particles Synergistically Enhance the Toughness and Electrical Conductivity in Hydrophobic Associated Hydrogels.

Abstract: Soft, conductive, and stretchable sensors are highly desirable in many applications, including artificial skin, biomonitoring patches, and so on. Recently, a combination of good electrical and mechanical properties was regarded as the most important evaluation criterion for judging whether hydrogel sensors are suitable for practical applications. Herein, we demonstrate a novel carboxylated carbon nanotube (MWCNT-COOH)-embedded P(AM/LMA)/SiO2@PANI hydrogel. The hydrogel benefits from a double-network structure (hydrogen bond cross-linking and hydrophobic connectivity network) due to the role of MWCNT-COOH and SiO2@PANI as cross-linkers, thus resulting in tough composite hydrogels. The obtained P(AM/LMA)/SiO2@PANI/MWCNT-COOH hydrogels exhibited high tensile strength (1939 kPa), super stretchability (3948.37%), and excellent strain sensitivity (gauge factor = 11.566 at 100-1100% strain). Obviously, MWCNT-COOH not only improved the electrical conductivity but also enhanced the mechanical properties of the hydrogel. Therefore, the integration of MWCNT-COOH and SiO2@PANI-based hydrogel strain sensors will display broad application in sophisticated intelligence, soft robotics, bionic prosthetics, personal health care, and other fields using inexpensive, green, and easily available biomass.

Development of Conductive Hydrogels for Fabricating Flexible Strain Sensors.

Abstract: Conductive hydrogels can be prepared by incorporating various conductive materials into polymeric network hydrogels. In recent years, conductive hydrogels have been developed and applied in the field of strain sensors owing to their unique properties, such as electrical conductivity, mechanical properties, self-healing, and anti-freezing properties. These remarkable properties allow conductive hydrogel-based strain sensors to show excellent performance for identifying external stimuli and detecting human body movement, even at subzero temperatures. This review summarizes the properties of conductive hydrogels and their application in the fabrication of strain sensors working in different modes. Finally, a brief prospectus for the development of conductive hydrogels in the future is provided.

Dually cross-linked single network poly(ionic liquid)/ionic liquid ionogels for a flexible strain-humidity bimodal sensor.

Abstract: Gel electrolytes have aroused extensive interest for diverse flexible electronics due to their high ionic conductivity and inherent stretchability. However, gel electrolytes still face challenges in terms of mechanical properties, fatigue resistance, and environmental adaptation, which severely limit the practical application of gel-based electronics. In this paper, we have synthesized a novel polymerizable ionic liquid [SBMA][AA] by mixing zwitterionic sulfobetaine methacrylate with acrylic acid. Then a dually cross-linked single network poly(ionic liquid)/ionic liquid (DCSN PIL/IL) ionogel was prepared by a simple one-step photopolymerization of the [SBMA][AA] in another IL 1-ethyl-3-methylimidazolium dicyanoamide ([EmIm][DCA]). The synergistic effect between covalent crosslinking and dynamic physical crosslinking points endows the ionogel with good mechanical properties as well as outstanding fatigue resistance. Gratifyingly, the entrapment of [EmIm][DCA] in the ionogel matrix yields excellent environmental adaptability and high ionic conductivity. Meanwhile, the DCSN PIL/IL ionogel also exhibited strong adhesive capacity due to the abundance of carboxyl and sulphonic acid groups. The outstanding electromechanical properties make the DCSN PIL/IL ionogel a perfect candidate for strain sensors to monitor diverse human body activities, such as the movement of the thumb knuckle and handwriting. Interestingly, the DCSN PIL/IL ionogel also displayed high responsiveness to humidity. Therefore, it is believed that this DCSN PIL/IL ionogel offers a broad prospect in flexible strain-humidity bimodal sensors.

Hypersensitized Strain Sensors Based on Conductive Hydrogels with Excellent Conductivity and Good Mechanical Properties

Abstract: As the essential substrates for the manufacture of flexible electronic devices, conductive hydrogels have shown great potential in the fields of flexible strain sensors, wearable devices, and electronic skin. However, their application is greatly limited by the poor mechanical properties, low conductivity, and sensitivity. In this work, we present a facile approach for preparing sensitive hydrogel-based sensors with stretchability, excellent conductivity, and suitability for detecting small strains by reducing silver particles through aqueous in situ reduction on the surface of lignosulfonate/polyvinyl alcohol composite hydrogels. The resulting hydrogel shows an excellent conductivity of 3300 S·m–1 and the tensile stress and strain at a break are 0.91 MPa and 380%, respectively. Furthermore, the conductive hydrogel exhibits high sensitivity (a gauge factor of 33.81 at 0–20% strain), linearity (R2 = 0.9952), fast response (<20 ms), and good durability (100 cycles). The sensing mechanism of a conductive hydrogel is analyzed to be the generation and recovery of microcracks in the silver layer. The strain sensors composed of conductive hydrogels demonstrate superior sensing performance by detecting subtle vibrations, human pulses, and tiny phonations of different persons. Therefore, it is believed that the conductive hydrogel has great potential applications in human activity monitoring and soft robotics.