ABSTRACT
Inspired by the interlocked biological geometry of human skin, herein, we design a flexible and transparent sensor with interlocked square column arrays with composites of Ag nanoparticles (AgNPs), citric acid (CA), and poly(vinyl alcohol) (PVA), which exhibit multisensory capabilities for pressure, temperature, and humidity. As a flexible pressure sensor, the interlocked AgNPs/CA/PVA sensor possesses a high sensitivity (-1.82 kPa-1), low detection limit (10 Pa), fast response (75 ms), and outstanding stability due to the high sensitivity of the contact resistance of the interlocked square column arrays to pressure. Because of the rigid dependence of the resistance of the AgNPs/CA/PVA composite on temperature, the interlocked AgNPs/CA/PVA sensor can also act as a temperature sensor, which exhibits high resolution (0.1 °C) and reliability in detecting ambient temperature. In addition, it is found that the amount of water molecules adsorbed by PVA and CA changes with the ambient humidity. Therefore, the interlocked AgNPs/CA/PVA sensor is also able to detect humidity in real time. This work proposes a simple but useful route to fabricate a flexible and transparent electrical skin sensor, which has great potential in the perception of pressure, temperature, and humidity.
ABSTRACT
Confined self-assembly of block copolymers (BCPs) is effective to manipulate various shapes of particles. In emulsion confined self-assembly, reversibly light-trigged switchable BCP particles are extremely expected, yet rarely reported. Herein, a novel strategy is developed to realize reversibly light-responsive shape-transformation of BCP particles by constructing functional surfactants with light-active azobenzene (azo) groups in the confined self-assembly of BCPs within emulsion droplet. Ultraviolet and visible lights can reversibly modulate the amphiphilicity and interfacial affinity of the surfactants to different blocks, triggering the reversible microphase structure transformation of BCP particles with high temporal-spatial resolution. We can realize shape and morphological transitions of BCP particles from onion-shaped spherical particles to striped ellipsoids and, ultimately, to inverse onion-like particles by ultraviolet irradiation. More importantly, this shape transformation is reversible by the irradiation of visible light, attributed to the reversible trans-cis isomerization of azo groups. We also demonstrate that the light-triggered shape transformation of BCP particles can be employed in a controllable drug release through a noncontacted and programmed manner, showing promising potential in clinic and biomedicine.
Subject(s)
Light , Polymers , Drug Liberation , Emulsions , Polymers/chemistry , Surface-Active Agents/chemistryABSTRACT
OBJECTIVE: The aim of this study was to screen hemicellulose degrading microorganisms. METHODS: The methods used to screen the effective strains included hydrolysis spot diameter measurement of hemicellulose plate and extracellular enzyme activity. The methods used to identify the strains included culture characteristics, morphological, physiological-biochemical characteristics and molecular biological methods. RESULTS: We isolated 4 actinomycetes (NA9, NA10, NA12 and NA13), 2 fungi (NF1 and NF7) with hemicellulose degrading ability and no antagonistic effect among them. The hemicellulose degrading activity of 4 actinomyces (NA9, NA10, NA12 and NA13) was 217.6, 229.8, 221.1 and 211.8 U/mL. The hemicellulose degrading activity of 2 fungi (NF1 and NF7) was 217.7 and 244.2 U/mL. The hemicellulose degrading activity of complex microbial system was 299.0 U/mL. NA9, NA10, NA12 and NA13 were Streptomyces costaricanus; NF1 was Aspergillus candidus and NF7 was Tarlaromyces flavus. CONCLUSION: the 4 actinomyces and 2 fungi screened have high hemicelluloses enzyme activity. These strains have good application value and more research value.