Transfer printing is a critical procedure for manufacturing stretchable electronics.During such a procedure,stamps are utilized to transfer micro devices from silicon wafers to stretchable polymeric substrates.In addition to conventional silicone rubber stamps,epoxy resin based shape memory stamps have been developed and the transfer yield is thus significantly promoted.However,elastic modulus of the epoxy stamps is too high at both glassy and rubbery states,which may break the brittle micro devices during the adhesion process under mechanical pressure.In this work,we synthesized a copolymer of butyl acrylate (BA) and polycaprolactone diacrylate (PCLDA) as a soft reversible dry adhesive enabling a shape memory capability based on crystalline transition of polycaprolactone (PCL) segments.For the sample containing 40 wt% BA and 60 wt% PCLDA,Young's modulus was 8.3 and 0.9 MPa respectively below and above the thermal transition temperature,which was much lower than that of the epoxy adhesive.On the other hand,the soft material still provided nearly ideal shape memory fixity and recovery ratios.Subsequently,shape memory surface with cone-shaped microstructure was prepared,which enabled a heating induced strong-to-weak adhesion transition when the microstructure recovered from a pressed temporary morphology to the permanent cone-shaped morphology.Such a soft reversible dry adhesive may contribute to large-scale and automated transfer printing processing. 相似文献
Two compounds, 9,10‐bis[2‐(quinolyl)vinyl]anthracene (BQVA) and 9,10‐bis[2‐(naphthalen‐2‐yl)vinyl]anthracene (BNVA), have been synthesised and investigated. Both of them have aggregation‐induced enhanced emission (AIEE) properties. Heteroatom‐assisted BQVA shows solvatochromism, reversible chromism properties and self‐assembly effects. When increasing the solvent polarities, the green solution of BQVA turns to orange with a redshift of the fluorescence emission wavelengths from λ=527 to 565 nm. Notably, BQVA exhibits reversible chromism properties, including mechano‐ and thermochromism. The as‐prepared BQVA powders show green fluorescence (λem=525 nm) and the colour can turn into orange (λem=573 nm) after grinding. Interestingly, the orange colour can return at high temperature. Based on these reversible chromism properties, a simple and convenient erasable board has been designed. Different from BQVA, non‐heteroatom‐assisted BNVA has no clear chromic processes. The results obtained from XRD, differential scanning calorimetry, single‐crystal analysis and theoretical calculations indicate that the chromic processes depend on the heteroatoms in BQVA. Additionally, BQVA also exhibits excellent self‐assembly effects in different solvents. Homogeneous nanospheres are formed in mixtures of tetrahydrofuran and water, which are then doped into silica nanoparticles and treated with 3‐aminopropyltriethoxysilane to give amino‐functionalised nanoparticles (BQVA?AFNPs). The BQVA?AFNPs could be used to stain protein markers in polyacrylamide gel electrophoresis. 相似文献
A novel pH sensitive shape‐memory polymer (SMP) is prepared by cross‐linking the β‐cyclodextrin modified alginate (β‐CD‐Alg) and diethylenetriamine modified alginate (DETA‐Alg): The pH reversible β‐CD‐DETA inclusion complexes serve as a reversible phase, and the cross‐linked alginate chains serve as a fixing phase. It is shown that this material can be processed into temporary shape as we needs at pH 11.5 and recover to its initial shape at pH 7. The recovery ratio and the fixity ratio were 95.7 ± 0.9% and 94.8 ± 1.1%, respectively. Furthermore, this material showed good degradability and biocompatibility. Because the shape transition pH value is quite close to that of our body fluid and this pH triggered shape‐memory effect is convenient and safe to use, this material has a high potential for medical application. 相似文献
A novel redox‐induced shape‐memory polymer (SMP) is prepared by crosslinking β‐cyclodextrin modified chitosan (β‐CD‐CS) and ferrocene modified branched ethylene imine polymer (Fc‐PEI). The resulting β‐CD‐CS/Fc‐PEI contains two crosslinks: reversible redox‐sensitive β‐CD‐Fc inclusion complexes serving as reversible phases, and covalent crosslinks serving as fixing phases. It is shown that this material can be processed into temporary shapes as needed in the reduced state and recovers its initial shape after oxidation. The recovery ratio and the fixity ratio are both above 70%. Furthermore, after entrapping glucose oxidase (GOD) in the system, the material shows a shape memory effect in response to glucose. The recovery ratio and the fixity ratio are also above 70%.
Chromism, generally a reversible color change of substances, finds vital applications in the fields of switching, catalysis, molecule binding, drug delivery and energy storage applications. Chromism is caused by the change of electronic, conformational, crystal or physical structure of materials due to heat, light, solvent/vapour, applied electric potential, etc. There have been observed different types of chromism such as thermochromism, photochromism, solvetochromism, electrochromism and many others from different compounds. Here in we have discussed different types of chromisms but in brief as inherited by various types of materials. Reversible multicolor chromism by metal halide formamidinium perovskite attests solvetochromism and thermochromism due to the hydrogen bonding. Tetrathiazolylthiophene compound shows mechanochromism because of the structural deformation. Chain length of ligand influences the chromism in copper complex. Gold cluster complex, boron complex, Bi2WO6 also display specific chromic performance. Phosphomolybdate – malachite green dye moiety (PMMG) displays hydrochromism because of bridged water molecules. N2 (or O2) binding to PMMG has recently been shown as an extension of hydrochromism phenomonon. Thus, this account on chromism from various materials is expected to attract the attention of researchers. 相似文献
Novel thermoplastic shape memory blends of ternary copolymerized polyamide (PAM) and maleated polyethylene (PE-g-MAH) were prepared by a simple melt-blending method, which might provide a new way for the industrial production of thermoplastic shape memory materials. The new chemical bonds were generated between PAM and PE-g-MAH, which was essential for enhancement of properties. The mechanical, thermal and shape memory properties of the blends were investigated in detail. It was found that the microstructure and proportion of different constituents was vital for the shape memory properties of the blends. In PAM/PE-g-MAH blends, a crystalline region of PAM acted as a fixed domain, and the crystalline region in PE-g-MAH acted as a reversible domain. The synergistic effect of the fixed and reversible domains determined the shape memory behavior of the blends. When the blend ratio of PAM/PE-g-MAH was 30/70, the composites exhibited the best shape memory properties, with a shape fixity ratio of 95.5% and a shape recovery ratio of 79.8%. 相似文献
In recent years, shape memory polyurethane (SMPU) as a smart material has been used in various applications owing to its desirable shape memory effect and biocompatibility. In this study, unidirectional SMPU nanofibers are innovated by electrospinning to clarify the mechanical and shape memory properties with nanofiber directions. The results showed that when the nanofiber alignment degree is 0° (parallel to the tensile direction), the aligned SMPU nanofibers achieved the obvious improvement of tensile strength (increased to 135%) and elastic modulus (increased to 313%), compared with the random SMPU nanofiber. Moreover, the developed aligned nanofibers exhibited good ability against stress relaxation and creep under constant strain or constant stress conditions in cyclic loading. The aligned SMPU nanofibers with a 0° alignment degree exhibited excellent shape memory properties with shape recovery rates larger than 93% and shape fixity rates larger than 90%, and a dramatic increase of shape recovery stress. 相似文献