Elastic Properties of Low-Dimensional Single-Crystalline Dielectric Oxides through Controlled Large-Area Wrinkle Generation.

Freestanding single-crystalline SrTiO3 membranes, as high-κ dielectrics, hold significant promise as the gate dielectric in two-dimensional (2D) flexible electronics. Nevertheless, the mechanical properties of the SrTiO3 membranes, such as elasticity, remain a critical piece of the puzzle to adequately address the viability of their applications in flexible devices. Here, we report statistical analysis on plane-strain effective Young's modulus of large-area SrTiO3 membranes (5 × 5 mm2) over a series of thicknesses (from 6.5 to 32.2 nm), taking advantage of a highly efficient buckling-based method, which reveals its evident thickness-dependent behavior ranging from 46.01 to 227.17 GPa. Based on microscopic and theoretical results, we elucidate these thickness-dependent behaviors and statistical data deviation with a bilayer model, which consists of a surface layer and a bulk-like layer. The analytical results show that the ∼3.1 nm surface layer has a significant elastic softening compared to the bulk-like layer, while the extracted modulus of the bulk-like layer shows a variation of ∼40 GPa. This variation is considered as a combined contribution from oxygen deficiency presenting in SrTiO3 membranes, and the alignment between applied strain and the crystal orientation. Upon comparison of the extracted elastic properties and electrostatic control capability to those of other typical gate dielectrics, the superior performance of single-crystalline SrTiO3 membranes has been revealed in the context of flexible gate dielectrics, indicating the significant potential of their application in high-performance flexible 2D electronics.

Antifatigue Hydration-Induced Polysaccharide Hydrogel Actuators Inspired by Crab Joint Wrinkles.

Joint wrinkles in animals facilitate frequent bending and contribute to the duration of the joint. Inspired by the morphology and function of joint wrinkles, we developed a bionic hydration-induced polymeric actuator with constructed wrinkles at the selected area. Specifically, we adopt electrical writing to create defined single and double cross-linking regions on chitosan (CS) hydrogel. The covalent cross-linking network was constructed by electrical writing-induced covalent cross-linking between CS chains and epichlorohydrin. Subsequent treatment of sodium dodecyl sulfate allows electrostatic cross-linking at the unwritten area with the simultaneous formation of surface wrinkles. The resulting single and double cross-linking hydrogel demonstrates spontaneous deformation behaviors by the influx and efflux of H2O to the electrostatic cross-linking domain under different ion concentrations. Importantly, the wrinkle structure endows the hydrogel with extraordinary antifatigue bending performance. By regulating the surface morphology and spatial cross-linking, we can design novel biomimetic polysaccharide hydrogel actuators with fascinating functions.

Effect of Copolymer on the Wrinkle Structure Formation and Gloss of a Phase-Separated Ternary Free-Radical/Cationic Hybrid System for the Application of Self-Matting Coatings.

Hybrid free-radical/cationic systems can generate phase-separated polymers or interpenetrating networks driven by photopolymerization. In this study, phase separation of a ternary mixture composed of a polybutadiene urethane diacrylate (PBUDA), a cycloaliphatic diepoxyde (CE), and hexanediol dimethacrylate (HDDMA) was investigated. Using systematic variations of the initial composition of the mixture, a miscibility phase diagram of the ternary mixture was established. Based on this diagram, a reactive copolymer (poly(butyl acrylate-co-glycidyl methacrylate) (PBGMA)) was introduced in a reference hybrid system to manipulate the crosslinking network, polymer morphology, and properties (e.g., roughness, gloss, strain at break, and glass transition temperature Tg). When cured as a coating, the ternary hybrid system showed a depthwise gradient of epoxy conversion, and thereby developed a mostly cured skin above a viscous sublayer of uncured monomer. This skin can develop compressive stress due to the swelling from the diffusion of unreacted monomers beneath, and if the compressive stress is significantly high, wrinkles appear on the coating's surface. This work highlights how both skin thickness and elastic modulus impact wrinkle frequency and amplitude. It was demonstrated that these wrinkle parameters can be manipulated in the ternary system by the addition of PBGMA. We also demonstrated that by employing UV irradiation and varying the PBGMA content, it is possible to engineer coatings that range from smooth surfaces with high gloss to wrinkled topographies with a very low associated gloss.

Clinical effect of nanofat on improving superficial rhytides of face and neck and dark lower eyelids / 中华医学美学美容杂志

Objective To evaluate the clinical effect of nanofat on superficial rhytides of face and neck and dark lower eyelids.Methods From September 2014 to January 2017,a total of 86 cases were collected in our hospital for voluntary nanofat transplantation on superficial rhytides and dark lower eyelids.This was a retrospective study,which included 18 cases of eye wrinkles,14 cases of forehead wrinkles,neck wrinkles in 14 cases,and 22 cases of dark lower eyelids.First of all,we harvested mircofat through liposuction,and then transformed mircofat to nanofat.At last,nanofat was grafted into intradermal layer of the skin with sharp needles.We took the standard photographs of the patients.After six months follow-up,doctors and patients evaluated the short term and long-term postoperative effect.Results No serious complications occurred in all patients.Postoperative evaluation of facial and neck superficial wrinkles showed that the satisfactory rate of doctors and patients after one month,was 85.9％and 84.3％,and after 6 months 87.5％ and 84.3％,respectively.Postoperative evaluation of dark lower eyelids showed that the satisfactory rate of doctors and patients after one month was 45.5％ and 36.4％,and after 6 months 81.8％ and 86.4％,respectively.Conclusions Nanofat can rectify the superficial rhytides of face and neck and dark lower eyelids in some patients.However,for some patients the effect is not satisfied.