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1. Inverse Elastocaloric Output in Supramolecular Liquid Crystalline Elastomers

   https://doi.org/10.1021/acsmaterialslett.5c00331  

   Saeed, Mohsin Hassan; Herman, Jeremy A; Das, Avijit; Kennedy, David T; White, Timothy J (August 2025, ACS Materials Letters)

   NoElastocaloric cooling is a promising solid-state alternative to vapor-compression refrigeration. In conventional systems, such as natural rubber, deformation induces entropy change accompanied by temperature release. Unloading the material restores the entropic state and is accompanied by cooling. Inverse elastocaloric effects have been detailed in shape memory alloys, where deformation induces loss of order and cooling. Here, we report on a distinctive inverse elastocaloric effect in liquid crystalline elastomers (LCEs) containing supramolecular hydrogen bonds. Upon deformation, the supramolecular LCE exhibits initial organization but then disorganizes as the intramesogenic hydrogen bonds are broken. Due to the liquid crystalline nature of the dimeric supramolecular bonds, the mechanochemical bond breakage manifests in a disruption in order. By disrupting the extent of liquid crystallinity in the system, we hypothesize that the network disorganizes to the deformation (e.g., entropy increases) and produces an inverse elastocaloric output.t Available 

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2. Influence of uniaxial compression on the shape memory behavior of vitrimer composite embedded with tension‐programmed unidirectional shape memory polymer fibers

   https://doi.org/10.1002/app.50429  

   Afful, Henry Quansah; Ibekwe, Samuel; Mensah, Patrick; Li, Guoqiang (December 2020, Journal of Applied Polymer Science)

   Abstract Tension programmed shape memory polymer (SMP) fibers have been used as sutures for closing wide‐opened cracks per the close‐then‐heal strategy. However, the composite may be subjected to compression loading during service. These compression loads can reduce the amount of recoverable strain in these pre‐tensioned fibers, limiting their ability to close cracks. The purpose of this study is to investigate the effect of in‐service compression loading on the shape memory effect (SME) of composites consisting of SMP fiber and SMP matrix. To this end, pre‐stretched shape memory Polyethylene Terephthalate (PET) fibers were embedded into a shape memory vitrimer to obtain composite samples with different fiber volume fractions. The SME of both the PET fiber and the vitrimer was investigated. The effect of compression load on the SME of the composite was studied. It is found that, uniaxial compression on the composite along the fiber direction significantly reduced the shrinking ability of the embedded pre‐tensioned SMP fibers. Hence, this is a factor that needs to be considered when designing such types of self‐healing composites. 

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3. Affordable lab-scale electrospinning setup with interchangeable collectors for targeted fiber formation

   https://doi.org/10.1016/j.ohx.2023.e00501  

   Switz, Alexi; Mishra, Aditi; Jabech, Katrina; Prasad, Anamika (March 2024, HardwareX)

   The electrospinning method is increasingly in demand due to its capability to produce fibers in the nanometer to micrometer range, with applications in diverse fields including biomedical, filtration, energy storage, and sensing. Many of these applications demand control over fiber layout and diameter. However, a standard flat plate collector yields random fibers with limited control over diameter and density. Other viable solutions offering a higher level of control are either scarce or substantially expensive, impeding the accessibility of this vital technique. This study addresses the challenge by designing an affordable laboratory-scale electrospinning setup with interchangeable collectors, enabling the creation of targeted fibers from random, aligned, and coiled. The collectors include the standard flat plate and two additional designs, which are a rotating drum and a spinneret tip collector. The rotating drum collector has adjustable speed control to collect aligned fibers and exhibits stability even at high rotational speeds. The spinneret tip collector was designed to produce helically coiled fibers. The setup was validated by directed fiber formation using polycaprolactone (PCL), a biodegradable and FDA-approved polymer. Overall, the uniqueness of the design lies in its affordability, modifiability, and replicability using readily available materials, thus extending the reach of the electrospinning technique. 

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4. Necking and drawing of rubber–plastic bilayer laminates

   https://doi.org/10.1039/C8SM00684A  

   Ramachandran, Rahul G.; Hariharakrishnan, S.; Fortunato, Ronald; Abramowitch, Steven D.; Maiti, Spandan; Velankar, Sachin S. (January 2018, Soft Matter)

   We examine the stretching behavior of rubber–plastic composites composed of a layer of styrene–ethylene/propylene–styrene (SEPS) rubber, bonded to a layer of linear low density polyethylene (LLDPE) plastic. Dog-bone shaped samples of rubber, plastic, and rubber–plastic bilayers with rubber : plastic thickness ratio in the range of 1.2–9 were subjected to uniaxial tension tests. The degree of inhomogeneity of deformation was quantified by digital image correlation analysis of video recordings of these tests. In tension, the SEPS layer showed homogeneous deformation, whereas the LLDPE layer showed necking followed by stable drawing owing to its elastoplastic deformation behavior and post-yield strain hardening. Bilayer laminates showed behavior intermediate between the plastic and the rubber, with the degree of necking and drawing reducing as the rubber : plastic ratio increased. A simple model was developed in which the force in the bilayer was taken as the sum of forces in the plastic and the rubber layers measured independently. By applying a mechanical energy balance to this model, the changes in bilayer necking behavior with rubber thickness could be predicted qualitatively. 

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5. Moisture Sensitive Smart Yarns and Textiles from Self‐Balanced Silk Fiber Muscles

   https://doi.org/10.1002/adfm.201808241  

   Jia, Tianjiao; Wang, Yang; Dou, Yuanyuan; Li, Yaowang; Jung_de_Andrade, Monica; Wang, Run; Fang, Shaoli; Li, Jingjing; Yu, Zhou; Qiao, Rui; et al (March 2019, Advanced Functional Materials)

   Abstract Smart textiles that sense, interact, and adapt to environmental stimuli have provided exciting new opportunities for a variety of applications. However, current advances have largely remained at the research stage due to the high cost, complexity of manufacturing, and uncomfortableness of environment‐sensitive materials. In contrast, natural textile materials are more attractive for smart textiles due to their merits in terms of low cost and comfortability. Here, water fog and humidity‐driven torsional and tensile actuation of thermally set twisted, coiled, plied silk fibers, and weave textiles from these silk fibers are reported. When exposed to water fog, the torsional silk fiber provides a fully reversible torsional stroke of 547° mm⁻¹. Coiled‐and‐thermoset silk yarns provide a 70% contraction when the relative humidity is changed from 20% to 80%. Such an excellent actuation behavior originates from water absorption‐induced loss of hydrogen bonds within the silk proteins and the associated structural transformation, which are corroborated by atomistic and macroscopic characterization of silk and molecular dynamics simulations. With its large abundance, cost‐effectiveness, and comfortability for wearing, the silk muscles will open up additional possibilities in industrial applications, such as smart textiles and soft robotics. 

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