Ultrastable and supersensitive conductive hydrogels conferred by "sodium alginate stencil" anchoring strategy.

Although conductive hydrogels have been widely developed currently, their low sensitivity and poor stability severely limited their practical application in flexible wearable devices. Herein, a green "stencil" anchoring strategy was proposed in this study to engineer an ultra-stable and supersensitive hydrogel by virtue of polydopamine decorating sodium alginate molecular chains as "stencil" to anchor polyaniline as conductive component. The dispersion of polyaniline was significantly improved by the sodium alginate "stencil" in the conductive hydrogel. The developed conductive hydrogel exhibited outstanding properties that outperformed most conventional ones, including extraordinary sensitivity with a gauge factor of 38.2 and excellent stability with negligible shifting upon long-term cyclic stretching. Moreover, the conductive hydrogel displayed great self-adhesion and reliable self-healing performance endowed by its abundant catechol groups, hydrogen bondings and π-π stackings, respectively. Furthermore, the prepared hydrogel was also assembled as flexible strain and self-powered sensors, which displayed excellent sensing performance, indicating great potential in human-machine interactions, information transmission and road transportation.

Mechanism of heparin interference in detection of LIAISON® Rubella IgM.

AIMS: To investigate the effects of heparin in detection of LIAISON® Rubella IgM (Rub-M) and the mechanism of interference. METHODS: Different concentrations of lithium heparin and sodium heparin were added to ten serum samples. The relative light units (RLU) value of Rub-M was measured using the LIAISON XL detection system. Different levels of IgM serum were incubated with magnetic particle in Rub-M detection kit at 4 °C for 4 h, blocking anti-human IgM-specific antibodies coated on the surface of magnetic particle. Separately, the rubella virus antigen in Rub-M detection kit was replaced by phosphate-buffered saline (PBS). The RLU values of LIAISON® Rub-M of original serum and serum containing various concentrations of heparin were measured after the above two different treatments. RESULTS: The RLU value of LIAISON® Rub-M increased with the increase of heparin content lower than 40 IU/mL, and reached a peak value at 40-50 IU/mL. The RLU value of LIAISON® Rub-M then decreased with the decrease of heparin concentration. When rubella virus antigen was replaced by PBS, the RLU value of LIAISON® Rub-M of serum samples containing 40 IU/mL heparin decreased significantly. The blocking concentration of IgM increased gradually, and the RLU value of LIAISON® Rub-M of seven serum samples containing 40 IU/mL heparin also decreased gradually. CONCLUSION: Plasma with heparin cannot be used to the detection of LIAISON® Rub-M. Heparin may participate in the reaction by binding with rubella virus antigen and anti-human IgM-specific antibodies coated on the surface of magnetic particle, thus affecting the detection results.

Smart sensing hydrogel actuators conferred by MXene gradient arrangement.

Smart sensing and excellent actuation abilities of natural organisms have driven scientists to develop bionic soft-bodied robots. However, most conventional robots suffer from poor electrical conductivity, limiting their application in real-time sensing and actuation. Here, we report a novel strategy to enhance the electrical conductivity of hydrogels that integrated actuation and strain-sensing functions for bioinspired self-sensing soft actuators. Conductive hydrogels were synthesized in situ by copolymerizing MXene nanosheets with thermosensitive N-isopropylacrylamide and acrylamide under a direct current electric field. The resulting hydrogels exhibited high electrical conductivity (2.11 mS/cm), good sensitivity with a gauge factor of 4.79 and long-term stability. The developed hydrogels demonstrated remarkable capabilities in detecting human motions at subtle strains such as facial expressions and large strains such as knee bending. Additionally, the hydrogel electrode patch was capable of monitoring physiological signals. Furthermore, the developed hydrogel showed good thermally induced actuation effects when the temperature was higher than 30 °C. Overall, this work provided new insights for the design of sensory materials with integrated self-sensing and actuation capabilities, which would pave the way for the development of high-performance conductive soft materials for intelligent soft robots and automated machinery.