Light-based 3D printing of stimulus-responsive hydrogels forminiature devices:recent progress and perspective

Miniature devices comprising stimulus-responsive hydrogels with high environmental adaptability are now considered competitive candidates in the fields of biomedicine,precise sensors,and tunable optics.Reliable and advanced fabricationmethods are critical formaximizing the application capabilities ofminiature devices.Light-based three-dimensional(3D)printing technology offers the advantages of a wide range of applicable materials,high processing accuracy,and strong 3D fabrication capability,which is suitable for the development of miniature devices with various functions.This paper summarizes and highlights the recent advances in light-based 3D-printed miniaturized devices,with a focus on the latest breakthroughs in lightbased fabrication technologies,smart stimulus-responsive hydrogels,and tunable miniature devices for the fields of miniature cargo manipulation,targeted drug and cell delivery,active scaffolds,environmental sensing,and optical imaging.Finally,the challenges in the transition of tunable miniaturized devices from the laboratory to practical engineering applications are presented.Future opportunities that will promote the development of tunable microdevices are elaborated,contributing to their improved understanding of these miniature devices and further realizing their practical applications in various fields.

Femtosecond laser direct writing of functional stimulus-responsive structures and applications

Diverse natural organisms possess stimulus-responsive structures to adapt to the surrounding environment.Inspired by nature,researchers have developed various smart stimulus-responsive structures with adjustable properties and functions to address the demands of ever-changing application environments that are becoming more intricate.Among many fabrication methods for stimulus-responsive structures,femtosecond laser direct writing(FsLDW)has received increasing attention because of its high precision,simplicity,true three-dimensional machining ability,and wide applicability to almost all materials.This paper systematically outlines state-of-the-art research on stimulus-responsive structures prepared by FsLDW.Based on the introduction of femtosecond laser-matter interaction and mainstream FsLDW-based manufacturing strategies,different stimulating factors that can trigger structural responses of prepared intelligent structures,such as magnetic field,light,temperature,pH,and humidity,are emphatically summarized.Various applications of functional structures with stimuli-responsive dynamic behaviors fabricated by FsLDW,as well as the present obstacles and forthcoming development opportunities,are discussed.

Stimulus-responsive mechanism of salt-responsive polymer and its application in saturated saltwater drilling fluid

AM-AMPS-TAC polymers with different charge distribution are synthesized using acrylamide(AM),2-acrylamido-2-methylpropanesulfonate(AMPS)and 3-acrylamidopropyl trimethylammonium(TAC)at different feed ratios by polymerization in solution.The salt-responsive behavior,reasons leading to salt-responsiveness,and effects of polymers molecular structure on salt-responsiveness are studied by laboratory experiments to find out the adaptability of the polymers.Rheology test under stepwise shear mode shows that the AM-AMPS-TAC polymers have salt responsiveness,and the closer the feeds of AMPS and ATC,the more significant the salt responsiveness will be.Conformation change of polymers molecular chain under salt stimulus is studied by turbidity test and micro-morphology analysis,and the responsive mechanism is further investigated by intrinsic viscosity test and copolymer composition analysis.Results indicate that the salt-responsive behavior of AM-AMPS-TAC polymers derives from the"curled to expanded"transition of chain conformation under salt stimulus,and this transition is led by the screening effect of salt which weakens polymers intramolecular ionic bond.Application in saturated saltwater drilling fluid shows that the AM90-AMPS5-TAC5 polymer has the best salt-tolerance and temperature-tolerance when used together with fluid loss controller PAC-Lv.The drilling fluid saturated with NaCl can maintain stable viscosity,good dispersion and low fluid loss for long time under 150℃.

Double stimulus-responsive palladium catalysts for ethylene polymerization and copolymerization

The external stimulus response strategy has been evolved rapidly in the field of olefin polymerization.In this work,we modularly synthesized three types of double stimulus responsiveα-diimine palladium catalysts,combining redox regulation and other regulation together,such as light,Lewis acid and alkali cations.The catalytic activities and the molecular weight of polyethylene products can be regulated for 4 times in ethylene polymerization.These palladium complexes were also used for the copolymerization reaction of ethylene and polar monomers,such as methyl 10-undecylenate and methyl acrylate,effectively regulating the catalytic activities,the molecular weight and polar monomer incorporation of the prepared copolymers.The research on these dual-regulated palladium complexes makes full use of prepared catalysts and provides new inspirations for regulating olefin polymerization.

Stimulus-responsive polymeric nanoparticles for biomedical applications

Polymeric nanoparticles with unique properties are regarded as the most promising materials for biomedical applications including drug delivery and in vitro/in vivo imaging.Among them,stimulus-responsive polymeric nanoparticles,usually termed as "intelligent" nanoparticles,could undergo structure,shape,and property changes after being exposed to external signals including pH,temperature,magnetic field,and light,which could be used to modulate the macroscopical behavior of the nanoparticles.This paper reviews the recent progress in stimulus-responsive nanoparticles used for drug delivery and in vitro/in vivo imaging,with an emphasis on double/multiple stimulus-responsive systems and their biomedical applications.

Stimulus-responsive room temperature phosphorescence in purely organic luminogens

Luminogens that exhibit stimulus-responsive room temperature phosphorescence(RTP)have attracted significant attention for their applications in a wide range of fields such as data storage,sensors,and bio-imaging.However,very few such materials are known,partly because of the unclear internal mechanism.In this review,we summarize recent advances in the field of stimulusresponsive RTP in purely organic luminogens,focusing on their unique emission behaviors and internal mechanisms governing the phenomena.We also attempt to identify the relationship between the mechanism,luminogens,and possible applications.

Stimulus-responsive polymers for safe batteries and smart electronics

Stimulus-responsive energy storage devices,which can respond to external stimuli,such as heat,pH,moisture,pressure,or electric field,have recently attracted intensive attention,aiming at the ever-increasing demand for safe batteries and smart electronics.The most typical stimulus-responsive materials are polymers that can change their conformation by forming and destroying secondary forces,including hydrogen bonds and electrostatic interactions in response to external stimuli,accompanied by changes in the intrinsic properties such as conductivity and hydrophobicity.Although the applications of stimulus-responsive functions in rechargeable batteries are still in the early stage because of the complexity and compatibility of battery architectures,many new concepts of regulating the polymer structures upon applications of stimuli have already been developed.In this review,we discuss the recent progress of stimulus-responsive polymers on energy storage devices featuring thermal protection and intelligent scenarios,with a focus on the detailed structural transformations of polymers under a given stimulus and the corresponding changes in battery performance.Finally,we present perspectives on the current limitations and future research directions of stimulus-responsive polymers for energy storage devices.

Circularly polarized luminescent self-organized helical superstructures:From materials and stimulus-responsiveness to applications

Circularly polarized luminescence(CPL)has gained considerable attention in various systems and has rapidly developed into an emerging research field.To meet the needs of actual applications in diverse fields,a high luminescence dissymmetry factor(glum)and tunable optical performance of CPL would be the most urgent pursuit for researchers.Accordingly,many emerging CPL materials and various strategies have been developed to address these critical issues.Emissive cholesteric liquid crystals(CLCs),that is,luminescent self-organized helical superstructures,are considered to be ideal candidates for constructing CPL-active materials,as they not only exhibit high glum values,but also enable flexible optical control of CPL.This review mainly summarizes the characteristics of CPL based on CLCs as the bulk phase doped with different emitters,including aggregated induced emission molecules,conventional organic small molecules,polymer emitters,metal-organic complex emitters,and luminescent nanoparticles.In addition,the recent significant progress in stimulus-responsive CPL based on emissive CLCs in terms of several types of stimuli,including light,electricity,temperature,mechanical force,and multiple stimuli is presented.Finally,a short perspective on the opportunities and challenges associated with CPL-active materials based on the CLC field is provided.This review is anticipated to offer new insights and guidelines for developing CLC-based CPL-active materials for broader applications.

INFLUENCE OF SHOT AND STEP RESPONSE ON PARAMETRIC SENSITIVITY UNDER THE STIMULUS-RESPONSE OF ANALYSIS

Shot and step response measurements were carried out with inert bed and adsorption bed both under iso-thermal conditions.Parameter values were determined from a time domain analysis of the measured inputand response signal.Sensitivity test in the parameter values showed that shot response measurements maygive more reliable parameter values than step measurements.Since Kubin[1]and Kucera[2]proposed a parameter estimation technique based on a moment methodfor adsorption system,attention has been focused on dynamic input-output measurements with variouspacked bed systems for the parameter estimation.The object of this work is to compare shot and step re-sponse measurements and see which measurement gives more reliable parameter values.

Legumain-triggered aggregable gold nanoparticles for enhanced intratumoral retention

Insufficient intratumoral retention of nanomedicines remains the major challenge for broad implementation in clinical sets.Herein,we proposed a legumain-triggered aggregable gold nanoparticle(GNP)delivery platform(GNPs-A&C).GNPs-A&C could form intratumoral or intracellular aggregates in response to the overexpressed legumain.The aggregates with size increase not only could reduce back-flow from interstitial space to peripheral bloodstream but also could restrict the cellular exocytosis,leading to enhanced intratumoral retention.In vitro studies demonstrated that GNPs-A&C possessed an excellent legumain responsiveness and the increased size was closely relevant with legumain expression.In vivo studies demonstrated GNPs-A&C possessed slower clearance rate and much higher intratumoral retention within legumain-overexpressed tumor compared to non-aggregable NPs,regardless of intravenous or intratumoral injection.More importantly,this delivery platform significantly improved the chemotherapeutic effect of doxorubicin(DOX)towards subcutaneous xenograft C6 tumor.The effectiveness of this stimulus-responsive aggregable delivery system provides a thinking for designing more intelligent size-tunable nanomedicine that can substantially improve intratumoral retention.

基于温度开关的光响应智能水凝胶用于可逆信息加密和解密

在智能凝胶防伪系统中使用的光、热、电、pH等刺激响应性水凝胶,是一种有前途的信息加密和解密材料.然而单一刺激会限制高水平的防伪.因此,需要协同使用多种刺激来提升信息安全等级.本研究设计了一种高透明度的海藻酸钠-聚丙烯酰胺(SA-PAM)水凝胶作为基体,利用无机变色材料钼酸铵(Mo7)赋予其凝胶光致变色特性.此外,温敏材料聚N-异丙基丙烯酰胺(PNIPAM)可使凝胶在最低临界相变温度(LCST)下发生体积相变,进而改变凝胶的宏观状态,可以通过调整凝胶体系中亲水单体和疏水单体的比例来控制LCST.利用紫外线(UV)作为“墨水”输入信息,以温度作为“开关”来加密/解密信息.总之,该水凝胶具有出色的光致变色能力,可在10 s内着色,紫外光吸收率最高可达96.23%.利用水凝胶对光-热刺激展现出的非凡响应能力,可以实现其迅速显示和隐藏信息的功能,从而确保信息安全,这为光致变色水凝胶在信息加密领域的应用提供了一种新方法.

Incorporating vehicle mix in stimulus-response car-following models

The objective of this paper is to incorporate vehicle mix in stimulus-response car-following models. Separate models were estimated for acceleration and deceleration responses to account for vehicle mix via both movement state and vehicle type. For each model, three submodels were developed for different pairs of following vehicles including ＂automobile following automobile,＂ ＂automobile following truck,＂ and ＂truck following automobile.＂ The estimated model parameters were then validated against other data from a similar region and roadway. The results indicated that drivers＇ behaviors were significantly different among the different pairs of following vehicles. Also the magnitude of the estimated parameters depends on the type of vehicle being driven and/or followed. These results demonstrated the need to use separate models depending on movement state and vehicle type. The differences in parameter estimates confirmed in this paper highlight traffic safety and operational issues of mixed traffic operation on a single lane. The findings of this paper can assist transportation professionals to improve traffic simulation models used to evaluate the impact of different strategies on ameliorate safety and performance of highways. In addition, driver response time lag estimates can be used in roadway design to calculate important design parameters such as stopping sight distance on horizontal and vertical curves for both automobiles and trucks.

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

The development of smart drug delivery systems(SDDSs)based on engineered nanomaterials is important for clinical applications.Nevertheless,controllable administration of chemotherapeutic drugs for deep tumors and the avoidance of side effects caused by off-targeting during delivery remain a great challenge.Herein,a stimulus-responsive system of mesoporous nanospheres(composed of Cu@Fe_(2)C@mSiO_(2))with good magnetothermal effect is introduced into the tumor microenvironment.This system plays an important role in image-guided controllable targeted drug delivery that is independent of tumor depth.Aggregation-induced emission luminogen-based fluorescence imaging and magnetic resonance imaging were utilized since these techniques visualize the delivery process in real time.In addition,the degraded nanocarriers showed high catalytic activity for Fenton and Fenton-like reactions,upregulating the level of hydroxyl radicals(•OH)in cancer cells to realize chemodynamic therapy.The induced•OH led to the overexpression of pho-STAT3,activating the STAT3 signaling pathway,eventually inducing cancer cell apoptosis.Through metabolic monitoring,this SDDS is removed from the body after its degradation in vivo.The synergistically enhanced therapeutic effect was obtained in the chemo-chemodynamic therapy of 4T1 tumor-bearing mice,offering a platform for efficient cancer therapy with a personalized theranostic strategy.

Advances in magnetic nanoparticle-based magnetic resonance imaging contrast agents

Magnetic resonance imaging(MRI)has revolutionized medical imaging diagnostics with the advantages of non-invasive nature,absence of ionizing radiation,unrestricted penetration depth,high-resolution imaging of soft tissues,organs and blood vessels,and multi-parameter and multi-sequence imaging.Contrast agents(CAs)are crucial for enhancing image quality,detecting molecular-level changes,and providing comprehensive diagnostic information in contrast enhanced MRI.However,the performance of clinical Gd-based CAs represents a limitation to the improvement of MRI sensitivity,specificity,and versatility,thereby impeding the achievement of satisfactory imaging outcomes.In recent years,the development of magnetic nanoparticle-based CAs has emerged as a promising avenue to enhance the capabilities of MRI.Here,we review the advances in magnetic nanoparticle-based MRI CAs,including blood pool CAs,biochemically-targeted CAs,stimulus-responsive CAs,and ultra-high field MRI CAs,as well as the use of CAs for cell labeling and tracking.Additionally,we offer insights into the future prospects and challenges associated with the integration of these nanoparticles into clinical practice.

High-entropy perovskite oxides:An emergent type of photochromic oxides with fast response for handwriting display

Stimulus-responsive materials are fundamental to the broad and ever-growing field of intelligence research,which bridge intelligent systems with the Internet of Things(loT)in future lifestyles.Among these materials,writable materials have received great interest;however,carbonization and irreversible writing processes are generally inevitable for extensively investigated organic compounds.Photochromism is a potential mode of composing information.Nevertheless,inorganic materials usually exhibit weak photochromic effects.Here,a novel strategy of designing high-entropy perovskite(HEP)oxides is put forward to develop a new inorganic photochromic system with satisfying performance.A series of HEP oxides are synthesized for the first time.Benefiting from excellent photochromic features,real-time information encoding was achieved.The mechanism-related photochromism is also discussed.Distinct from the previous works,it is believed that the present photochromic-based HEP oxides provide a new and manyfold research space for the future development of conventional writable materials and the disclosing of unprecedented properties and phenomena.

Highly emissive coordination polymer derived from tetraphenylethylene-tetrazole chromophore:Synthesis,characterization and piezochromic luminescent behavior

Solid-state materials that exhibit pressure stimulus-response characteristics in a manner of emission signal,known as piezochromic luminescence(PCL),demonstrate great potential in photoelectric devices.The weakened luminescence and insignificant color change in the aggregation state,however,hampers their practical applications.Herein,a highly emissive coordination polymer,[Zn2(H4TTPE)(H2O)4]·H2O(CUST-805),is successfully constructed by employing an AIE-active chromophore as the building block.The structural characterization and photophysical properties are systematically studied.Owing to intrinsic twisted conformation and AIE feature of tetraphenylethylene-tetrazole ligand,CUST-805 achieves the visible and reversible PCL from blue to green switched by different external stimuli.The transformation between crystalline and amorphous states is proved to be the origin of present PCL behavior.Moreover,on basis of electron and energy transfer quenching mechanism,the highly selective and sensitive sensor based on CUST-805 is realized,showing the low detection limit of 0.29 ppm towards 2,4,6-trinitrophenol.

Nanomedicines for the treatment of rheumatoid arthritis:State of art and potential therapeutic strategies

Increasing understanding of the pathogenesis of rheumatoid arthritis(RA)has remarkably promoted the development of effective therapeutic regimens of RA.Nevertheless,the inadequate response to current therapies in a proportion of patients,the systemic toxicity accompanied by longterm administration or distribution in non-targeted sites and the comprised efficacy caused by undesirable bioavailability,are still unsettled problems lying across the full remission of RA.So far,these existing limitations have inspired comprehensive academic researches on nanomedicines for RA treatment.A variety of versatile nanocarriers with controllable physicochemical properties,tailorable drug release pattern or active targeting ability were fabricated to enhance the drug delivery efficiency in RA treatment.This review aims to provide an up-to-date progress regarding to RA treatment using nanomedicines in the last 5 years and concisely discuss the potential application of several newly emerged therapeutic strategies such as inducing the antigen-specific tolerance,pro-resolving therapy or regulating the immunometabolism for RA treatments.

pH-sensitive zwitterionic improves tumor targeting efficacy coating of gold nanocages and photothermal treatment

Stealth coating materials effectively extend a nanoparticle＇s systemic circulation lifetime yet limit its cellular internalization, which promotes and prevents tumor targeting, respectively. Here, this contradiction was resolved by using an acutely pH-sensitive zwitterionic stealth ligand capable of responding to small differences in extracellular pH between blood and tumors. Using a photothermal gold nanocage （AuNC） as a model nanotherapeutic, we found that stealth-AuNC nanoparticles showed both significantly enhanced cell uptake efficiency in acidic tumors and a markedly extended systemic circulation lifetime compared to its unaltered analogue. As a result, stealth-AuNC nanoparticles administered intravenously showed significantly enhanced accumulation within the tumor, leading to significantly improved photothermal therapeutic efficacy in mouse models. These results suggests that pH-sensitive zwitterionic ligands with sufficient sensitivity for responding to small differences in extracellular pH between blood and tumors are ideal stealth materials for simultaneously conferring both extended systemic circulation and enhanced cellular internalization, reducing the need for active targeting moieties.

Antibody-activated trans-endothelial delivery of mesoporous organosilica nanomedicine augments tumor extravasation and anti-cancer immunotherapy

Tumor vasculature constitutes a formidable hurdle for the efficient delivery of cancer nanomedicine into tumors.The leverage of passive pathway through inter-endothelial gaps in tumor blood vessels might account for limited extravasation of nanomedicine into tumor microenvironment(TME).Herein,Annexin A1 antibody-installed mesoporous organosilica nanoplatforms carrying immunotherapeutics of anti-PD-L1 antibody(aPD-L1)and Indoximod are developed to target at caveolar Annexin-A1 protein of luminal endothelial cells and to trigger the active trans-endothelial transcytosis of nanomedicine mediated by caveolae.Such strategy enables rapid nanomedicine extravasation across tumor endothelium and relatively extensive accumulation in tumor interstitium.aPD-L1 and Indoximod release from aPD/IND@MON-aANN in a reduction-responsive manner and synergistically facilitate the intratumoral infiltration of cytotoxic T lymphocytes and reverse the immunosuppressive TME,thus demonstrating substantial anti-tumor efficacy in subcutaneous 4T1 breast tumors and remarkable anti-metastatic capacity to extend the survival of 4T1 tumor metastasis model.Moreover,aPD/IND@MON-aANN nanomedicine also exhibits distinct superiority over the combination therapy of free drugs to potently attenuate the progression of urethane-induced orthotopic lung cancers.Collectively,aPD/IND@MON-aANN nanoplatforms with boosted delivery efficiency via antibody-activated trans-endothelial pathway and enhanced immunotherapeutic efficacy provides perspectives for the development of cancer nanomedicines.

Organic crystal-based flexible smart materials

Although the famous brittle characteristics of molecular crystals are unfavorable when they are used as flexible smart materials(FSMs),an increasing number of organic crystal-based FSMs have been reported recently.This breaks the perception of their stiff and brittle properties and promises a bright future for basic research and practical applications.Crystalline smart materials present considerable advantages over polymer materials under certain circumstances,rendering them potential candidates for certain applications,such as rapidly responsive actuators,ON/OFF switching,and microrobots.In this review,we summarize the recent developments in the field of organic crystal-based FSMs,including the derivatives of azobenzene,diarylethene,anthracene,and olefin.These organic crystal-based FSMs can bend,curl,twist,deform,or respond otherwise to external stimuli,such as heat or light.The detailed mechanisms of their smart behaviors are discussed with their potential applications in exciting intelligent fields.We believe this review could provide guidelines toward future fabrication and developments for novel organic crystal-based FSMs and their advanced smart applications.