Insights into the regulation mechanism of ring-shaped magnetoelectric energy harvesters via mechanical and magnetic conditions

This paper presents a theoretical model for predicting and tuning magnetoelectric(ME)effect of ring-shaped composites,in which stress boundary conditions are empoyed and the multi-field coupling property of giant magnetostrictive materials are taken into account.A linear analytical solutions for the closed-and open-circuit ME voltages are derived simultaneously using mechanical differential equations,interface and boundary conditions,and electrical equations.For nonlinear ME coupling effect,the nonlinear multi-field coupling constitutive equation is reduced to an equivalent form by expanding the strains as a Taylor series in the vicinity of bias magnetic field.Sequentially,the linear model is generalized to a nonlinear one involving the field-dependent material parameters.The results show that setting a stress-free condition is beneficial for reducing resonance frequency while applying clamped conditions on the inner and outer boundaries may improve the maximum output power density.In addition,performing stress conditions on one of the boundaries may enhance ME coupling significantly,without changing the corresponding resonance frequency and optimal resistance.When external stimuli like bias magnetic field and pre-stress are applied to the ring-shaped composites,a novel dual peak phenomenon in the ME voltage curve around resonance frequencies is revealed theoretically,indicating that strong ME coupling may be achieved within a wider bias field region.Eventually,the mutual coordination of the bias field and pre-stress may enhance ME coupling as well as tuning the resonance frequency,and thus is pivotal for tunable control of ME energy harvesters.The proposed model can be applied to design high-performance energy harvesters by manipulating the mechanical conditions and external stimuli.

Luminescence anti-counterfeiting:From elementary to advanced

Luminescence anti-counterfeiting derives from the easily changeable luminescence behaviors of luminescence materials under the regulation of various external stimuli(such as excitation light,chemical reagent,heat,and mechanical force,etc.)and luminescence lifetime,which plays an important role in preventing forgery of currency,artworks,and product brands.According to the numbers of changes of anti-counterfeiting labels under various regulation conditions,luminescence anti-counterfeiting can be classified into three levels from elementary to advanced:single-level anti-counterfeiting,double-level anti-counterfeiting,and multilevel anti-counterfeiting.In this review,the recent achievements in luminescence anti-counterfeiting are summarized,and the regulation of various factors to anti-counterfeiting labels is discussed.Finally,existing problems,future challenges,and possible development directions are proposed in order to realize facile,quick,low-cost,environmentally friendly,and difficult-to-replicate advanced luminescence anti-counterfeiting.

A Perspective:Electrospun Fibers for Repairing Spinal Cord Injury

Patients with spinal cord injury(SCI)are suffering disability and accompanying complications.Due to the complex biological processes and inhibitory microenvironment after SCI,advances in clinical treatment show obvious limitations for achieving a successful repair.Herein,we summarize recent advances in engineering strategies of using electrospun nanofibers to promote the neural regeneration and functional recovery after SCI.We firstly introduce the pathological mechanism of SCI and thus point out the challenges on the regeneration of the nerve.We then discuss the regenerative approaches by combining electrospun nanofibrous scaffolds with physical cues,biochemical cues(e.g.,cells,growth factors and other biomolecules),external stimuli,and supporting materials filling in the inner lumen of the scaffolds.All these strategies have indicated their potentials to enhance the efficacy of repairing the SCI.At last,we provide a perspective on the future direction for designing the electrospun nanofibrous scaffolds in combination with imaging systems to realize the in-situ monitoring of regeneration progress for further improving the treatment outcome.

Smart Bionic Surfaces with Switchable Wettability and Applications

In order to satisfy the needs of different applications and more complex intelligent devices,smart control of surface wettability will be necessary and desirable,which gradually become a hot spot and focus in the field of interface wetting.Herein,we review interfacial wetting states related to switchable wettability on superwettable materials,including several classical wetting models and liquid adhesive behaviors based on the surface of natural creatures with special wettability.This review mainly focuses on the recent developments of the smart surfaces with switchable wettability and the corresponding regulatory mechanisms under external stimuli,which is mainly governed by the transformation of surface chemical composition and geometrical structures.Among that,various external stimuli such as physical stimulation(temperature,light,electric,magnetic,mechanical stress),chemical stimulation(pH,ion,solvent)and dual or multi-triggered stimulation have been sought out to realize the regulation of surface wettability.Moreover,we also summarize the applications of smart surfaces in different fields,such as oil/water separation,programmable transportation,anti-biofouling,detection and delivery,smart soft robotic etc.Furthermore,current limitations and future perspective in the development of smart wetting surfaces are also given.This review aims to offer deep insights into the recent developments and responsive mechanisms in smart biomimetic surfaces with switchable wettability under external various stimuli,so as to provide a guidance for the design of smart surfaces and expand the scope of both fundamental research and practical applications.

Advanced strategies of scaffolds design for bone regeneration

Bone defects are encountered substantially in clinical practice,and bionic scaffolds represent a promising solution for repairing bone defects.However,it is difficult to fabricate scaffolds with bionic structures and reconstruct the microenvironment to fulfill the satisfying repair effects.In this review article,we first discuss various strategies for the design and construction of bionic scaffolds to promote bone defect repair,especially including the structural construction of the scaffold and the integration of bioactive substances together with the application of external stimuli.We then discuss the roles of artificial intelligence and medical imaging in aiding clinical treatment.Finally,we point out the challenges and future outlooks in developing multifunctional bone repair scaffolds,aiming to provide insights for improving bone regeneration efficacy and accelerating clinical translation.