Multifunctional Janus Microplates Arrays Actuated by Magnetic Fields for Water/Light Switches and Bio‐Inspired Assimilatory Coloration

Smart dynamic regulation structured surfaces, inspired by nature, which can dynamically change their surface topographies under external stimuli for convertible fluidic and optical properties, have recently motivated significant interest for scientific research and industrial applications. However, there is still high demand for the development of multifunctional dynamically transformable surfaces using facile preparation strategies. In this work, a type of Janus high‐aspect‐ratio magnetically responsive microplates array (HAR‐MMA) is readily fabricated by integrating a flexible laser scanning strategy, smart shape‐memory‐polymer‐based soft transfer, and a simple surface treatment. By applying external magnetic field, instantaneous and reversible deformation of Janus HAR‐MMA can be actuated, so surface wettability can be reversibly switched between superhydrophobic (158°) and hydrophilic (40°) states, based on which a novel magnetically responsive water droplet switch can be realized. Moreover, inspired by the biological assimilatory coloration of chameleons, dynamically color conversion can be skillfully realized by applying different colors on each side of the Janus HAR‐MMA. Finally, as a proof‐of‐concept demonstration in light manipulation, a HAR‐MMA is applied as an optical shutter actuated by external magnetic field with eximious controllability and repeatability. The developed multifunctional HAR‐MMA provides a versatile platform for microfluidic, biomedical, and optical applications.     

Light‐Driven Chiral Molecular Switches or Motors in Liquid Crystals

The ability to tune molecular self‐organization with an external stimulus is a main driving force in the bottom‐up nanofabrication of molecular devices. Light‐driven chiral molecular switches or motors in liquid crystals that are capable of self‐organizing into optically tunable helical superstructures undoubtedly represent a striking example, owing to their unique property of selective light reflection and which may lead to applications in the future. In this review, we focus on different classes of light‐driven chiral molecular switches or motors in liquid crystal media for the induction and manipulation of photoresponsive cholesteric liquid crystal systems and their consequent applications. Moreover, the change of helical twisting powers of chiral dopants and their capability of helix inversion in the induced cholesteric phases are highlighted and discussed in the light of their molecular geometric changes.     

Liposome Crosslinked Polyacrylamide/DNA Hydrogel: a Smart Controlled‐Release System for Small Molecular Payloads

A novel stimuli‐responsive hydrogel system with liposomes serving as both noncovalent crosslinkers and functional small molecules carriers for controlled‐release is developed. Liposomes can crosslink polyacrylamide copolymers functionalized with cholesterol‐modified DNA motifs to yield a DNA hydrogel system, due to the hydrophobic interaction between cholesteryl groups and the lipid bilayer of liposomes. Functional information encoded DNA motifs on the polymer backbones endow the hydrogel with programmable smart responsive properties. In a model system, the hydrogel exhibits stimuli‐responsive gel‐to‐sol transformation triggered by the opening of DNA motifs upon the presence of a restriction endonuclease enzyme, EcoR I, or temperature change, realizing the controlled‐release of liposomes which are highly efficient carriers of active small molecules payloads. Two active molecules, 1,1‐dioctadecyl‐3,3,3,3‐tetramethylindodicarbocyanine perchlorate (DiIC18(5)) and calcein, are chosen as the hydrophobic and hydrophilic model payloads, respectively, to address the feasibility of the releasing strategy. Moreover, the hydrogel exhibits injectable property as well as self‐recovery behaviors.     

A UV‐Responsive Multifunctional Photoelectric Device Based on Discotic Columnar Nanostructures and Molecular Motors

Orientation control of ordered materials would not only produce new physical phenomenon but also facilitate the development of fancy devices. Discotic liquid crystals (DLCs) form 1D charge transport pathway by self‐organizing into columnar nanostructures via π–π stacking. However, controlling the electrical properties in such nanostructures with some direct and instant way is a formidable task for their high viscosity and insensitivity to external stimuli. Herein, the arbitrary control over electrical conductivity of such columnar nanostructures is achieved with UV light by incorporating DLCs with molecular motors. Highly ordered DLC microstripe arrays are generated on desired substrate through a capillary bridge dewetting strategy. The conductivity of the microstripes could be continuously modulated by 365 nm light due to the influence of molecular motion under UV irradiation on the electron orbital overlap of columnar nanostructures. This is so because the disorder degree of the DLC molecules is associated with the intensity of UV light and the doping concentration of molecular motors. Moreover, the device shows memory effect and reversible conductivity change. The DLC microstripe arrays are very promising for the applications in UV detectors, memory devices, optical switches, and so on.     

Ce-Doped Smart Adsorbents with Photoresponsive Molecular Switches for Selective Adsorption and Efficient Desorption

Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive. However, it is difficult for traditional adsorbents to reach the target because of their fixed active sites. Herein, we report on the fabrication of a smart adsorbent, which was achieved by introducing photoresponsive azobenzene derivatives with cis/trans isomers to Ce-doped mesoporous silica. These photoresponsive groups serve as “molecular switches” by sheltering and exposing active sites, leading to efficient adsorption and desorption. Ce is also doped to provide additional active sites in order to enhance the adsorption performance. The results show that the cis isomers effectively shelter the active sites, leading to the selective adsorption of methylene blue (MB) over brilliant blue (BB), while the trans isomers completely expose the active sites, resulting in the convenient release of the adsorbates. Both selective adsorption and efficient desorption can be realized controllably by these smart adsorbents through photostimulation. Moreover, the performance of the obtained materials is well maintained after five cycles.     

Functional Materials and Systems for Rewritable Paper

“Paper” has greatly contributed to the development and spread of civilization. Even in today's “digitalized” world, paper continues to play a key role in socioeconomic growth, as is evidenced by the growth in global paper consumption. Unfortunately, the use of paper has its cost in terms of the exhaustion of world's natural resources. Consequently, new, cost‐effective technologies that preserve natural resources are required for this purpose. Functional materials have revolutionized the way people think about developing new technologies. Especially important in this regard are “smart reactive materials,” which are capable of actively responding to external stimuli such as heat, light, mechanical stress, and specific molecular orientations. Moreover, functionalized chromogenic materials, which undergo reversible color switching upon external stimulation, have attracted great attention in the context of developing rewritable paper. Here, investigations of various materials and systems that are devised for use as rewritable paper are reviewed with the hope that the coverage will stimulate and guide future studies in this area.     

25th Anniversary Article: Organic Electronics Marries Photochromism: Generation of Multifunctional Interfaces,Materials, and Devices

Organic semiconductors have garnered significant interest as key components for flexible, low‐cost, and large‐area electronics. Hitherto, both materials and processing thereof seems to head towards a mature technology which shall ultimately meet expectations and efforts built up over the past years. However, by its own organic electronics cannot compete or complement the silicon‐based electronics in integrating multiple functions in a small area unless novel solutions are brought into play. Photochromic molecules are small organic molecules able to undergo reversible photochemical isomerization between (at least) two (meta)stable states which exhibit markedly different properties. They can be embedded as additional component in organic‐based materials ready to be exploited in devices such as OLEDs, OFETs, and OLETs. The structurally controlled incorporation of photochromic molecules can be done at various interfaces of a device, including the electrode/semiconductor or dielectric/semiconductor interface, or even as a binary mixture in the active layer, in order to impart a light responsive nature to the device. This can be accomplished by modulating via a light stimulus fundamental physico‐chemical properties such as charge injection and transport in the device.     

Aptamer‐Directed Synthesis of Multifunctional Lanthanide‐Doped Porous Nanoprobes for Targeted Imaging and Drug Delivery

Multifunctional lanthanide‐doped porous nanoparticles are prepared via a facile one‐step solvothermal route by employing aptamers as the biotemplate. The nanoparticles feature excellent aqueous dispersibility and biospecific properties and could work as effective nanoprobes for targeted imaging and drug delivery. With aptamer being in principle available for any kind of target, this synthetic strategy may open the door to a new generation of nanoprobes for bioapplications such as time‐resolved biodetection, multimode bioimaging/biolabeling, and targeted cancer therapy.     

Optically Rewritable Transparent Liquid Crystal Displays Enabled by Light‐Driven Chiral Fluorescent Molecular Switches

Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. Herein, two novel light‐driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopants exhibit reversible reflection color tuning spanning the visible and infrared region of the spectrum. Transparent display devices have been fabricated using both low chirality and high chirality cholesteric films that operate either exclusively in fluorescent mode or in both fluorescent and reflection mode, respectively. The dual mode display device employing short pitch cholesteric film is able to function on demand under all ambient light conditions including daylight and darkness with fast response and high resolution. Moreover, the proof‐of‐concept for a “remote‐writing board” using cholesteric films containing one of the light‐driven chiral fluorescent molecular switches with ease of fabrication and operation is disclosed herein. Such optically rewritable transparent display devices enabled by light‐driven chiral fluorescent molecular switches pave a new way for developing novel display technology under different lighting conditions.     

A Smart Responsive Dual Aptamers‐Targeted Bubble‐Generating Nanosystem for Cancer Triplex Therapy and Ultrasound Imaging

The absence of targeted, single treatment methods produces low therapeutic value for treating cancers. To increase the accumulation of drugs in tumors and improve the treatment effectiveness, near‐infrared 808 nm photothermal responsive dual aptamers‐targeted docetaxel (DTX)‐containing nanoparticles is proposed. In this system, DTX and NH₄HCO₃ are loaded in thermosensitive liposomes. The surface of liposomes is coated with gold nanoshells and connected with sulfydryl (SH? ) modified AS1411 and S2.2 aptamers. The nanosystem has good biocompatibility and uniform size (diameter about 200 nm). The drug is rapidly released, reaching a maximum amount (84%) at 4 h under 808 nm laser irradiation. The experiments conducted in vitro and in vivo demonstrate the nanosystem can synergistically inhibit tumor growth by combination of chemotherapy, photothermal therapy, and biological therapy. Dual ligand functionalization significantly increases cellular uptake on breast cancer cell line (MCF‐7) cells and achieves ultrasound imaging (USI) at tumor site. The results indicate that this drug delivery system is a promising theranostic agent involving light‐thermal response at tumor sites, dual ligand targeted triplex therapy, and USI.     

DNA Origami‐Enabled Engineering of Ligand–Drug Conjugates for Targeted Drug Delivery

Effective drug delivery systems that can systematically and selectively transport payloads to disease cells remain a challenge. Here, a targeting ligand‐modified DNA origami nanostructure (DON) as an antibody–drug conjugate (ADC)‐like carrier for targeted prostate cancer therapy is reported. Specifically, DON of six helical bundles is modified with a ligand 2‐[3‐(1,3‐dicarboxy propyl)‐ureido] pentanedioic acid (DUPA) against prostate‐specific membrane antigen (PSMA), to serve as the antibody for drug conjugation in ADC. Doxorubicin (Dox) is then loaded to DON through intercalation to dsDNA. This platform features in spatially controllable organization of targeting ligands and high drug loading capacity. With this nanocomposite, selective delivery of Dox to the PSMA+ cancer cell line LNCaP is readily achieved. The consequent therapeutic efficacy is critically dependent on the numbers of targeting ligand assembled on DON. This target‐specific and biocompatible drug delivery platform with high maximum tolerated doses shows immense potential for developing novel nanomedicine.     

Distance‐Mediated Plasmonic Dimers for Reusable Colorimetric Switches: A Measurable Peak Shift of More than 60 nm

The first reconfigurable colorimetric DNA switches based on target DNA binding are reported. This DNA binding actuates a change in the interparticle distance between gold nanoparticle dimers. A significant spectral shift of 68 nm is achievable from on‐off switching. The reconfigurability is possible owing to thiol and EDC‐imidazole coupling which anchors the DNA linkers to the nanoparticles. The huge spectral shift allows the unaided eye to observe single target biomolecular binding event in real time under a darkfield microscope. The limit‐of‐detection for target molecules in PBS and human serum are 10^?13 M and 10^?11 M respectively. An improved fabrication strategy via asymmetric functionalization is also described, assisted by solid phase synthesis which minimizes the formation of trimers and multimers.