Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

A review of shape memory alloy research, applications and opportunities

Recent progress in shape memory polymer: New behavior, enabling materials, and mechanistic understanding

A review of stimuli-responsive shape memory polymer composites

This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

Soft Actuators for Small-Scale Robotics.

Recent advances in shape–memory polymers: Structure, mechanism, functionality, modeling and applications

Study of multi-functional electrospun composite nanofibrous mats for smart wound healing

Organic near infrared (NIR) persistent‐luminescence systems with bright and long‐lived emission are highly valuable for applications in communication, imaging, and sensors. However, realizing these materials (especially lifetime over 0.1 s) is a challenge, mainly because of non‐radiative quenching of their long‐lived excitons. Herein, a universal strategy of stepwise Förster resonance energy transfer (FRET) for a bright NIR system with remarkable persistent luminescence (up to 0.2 s at 810 nm) is presented, based on a new triphenylene‐dye‐doped polymer (triphenylene‐2‐ylboronic acid@poly(vinyl alcohol) (TP@PVA)) with a persistent blue phosphorescence of 3.29 s. This persistent NIR luminescence is demonstrated for application not only in NIR anti‐counterfeiting but also NIR bioimaging with penetrating a piece of skin as thick as 2.0 mm. By co‐doping a red dye (such as Nile red) and an NIR dye Cyanine 7 (Cy7) into this doped PVA film, the shortage of spectral overlap between TP emission and Cy7 absorbance is successfully solved, through a stepwise FRET process involving triplet to singlet (TS)‐FRET from TP to the intermediate red dye and then singlet to singlet (SS)‐FRET to Cy7. It is noted that the efficiency of the upper TS‐FRET is enhanced significantly by the lower SS‐FRET, leading to high efficiencies for the continuous FRETs.

Stepwise Energy Transfer: Near‐Infrared Persistent Luminescence from Doped Polymeric Systems

This article reports a chromic polymer, which is responsive to its shape memory properties and has both the behavior of shape memory polymers and chromic materials. We employed a strategy to fabricate such a smart material, which represents a new principle for making chromic materials. This material is made of shape memory polyurethane with tetraphenylethylene units (0.1 wt %) covalently connected to the soft-segments (PCL, Mw = 4000). The material displays biocompatibility, shape fixity of 88–93%, and almost 100% shape recovery and has reversible mechanochromic, solvatochromic, and thermochromic shape memory effect. The memory chromism represented by the reversible change of emission intensity shows negative correlation with shape fixity, temperature, and existence of solvent. It may be explained that when the soft segments are molten or dissolved in solvent, the shape recovery switch is open, the AIE units are free from crystal binding and can migrate easily to larger areas, thus the AIE units/particles are far apart from each other and the barrier for rotation of phenyl groups is reduced, which lead to the reduction of emission intensity, appeared by no colors or pale colors, and vice versa. Since the switch is a fundamental structural character of SMPs, the shape memory properties have led to the chromism and we call this memory chromic. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 104–110

Memory chromic polyurethane with tetraphenylethylene

The molecular structural design learned from natural materials enables synthetic polymers with desirable and unique features to be fabricated. Inspired by spider silks, short-chain polyalanine (PA) is introduced into multiblock biopolymers with poly(e-caprolactone) segments via a coupling reaction. As a result, PA segments in biopolymers form similar β-sheet crystals to that of natural spidroins. These new biopolymers are found to exhibit nearly complete shape recovery and high shape fixity, along with significantly improved thermal stability due to the strong β-sheet structures as netpoints. This work provides new insight for the design of novel shape-memory polymers with potential use in biomedical applications.

Huahua Huang

Papers

Recent advances in shape–memory polymers: Structure, mechanism, functionality, modeling and applications

Study of multi-functional electrospun composite nanofibrous mats for smart wound healing

Stepwise Energy Transfer: Near‐Infrared Persistent Luminescence from Doped Polymeric Systems

Memory chromic polyurethane with tetraphenylethylene

Shape‐Memory Biopolymers Based on β‐Sheet Structures of Polyalanine Segments Inspired by Spider Silks