#shape memory materials

Sustainable smart polymers change color and self-repair when damaged

Plastics, which are polymeric materials composed of long chains of small molecules called monomers, are widely used in everyday life and industry due to their lightweight, good strength and flexibility. However, with approximately 52 million tons of plastic waste generated annually, plastic pollution has become a major environmental concern. To address this issue, research efforts have focused on developing sustainable polymeric materials. Unfortunately, most materials developed so far suffer from complex synthesis processes or difficulties in separating them from other polymers during waste disposal. To overcome these limitations, a research team led by Dr. Tae Ann Kim of the Convergence Research Center for Solutions to Electromagnetic Interference in Future-mobility (SEIF) at Korea Institute of Science and Technology (KIST) has developed a new polymeric material with self-healing capabilities and high recyclability.

Researchers at Tohoku University have developed a groundbreaking titanium-aluminum (Ti-Al)-based superelastic alloy. This new material is not only lightweight but also strong, offering the unique superelastic capability to function across a broad temperature range -- from as low as -269°C, the temperature of liquid helium, to +127°C, which is above the boiling point of water. This discovery holds significant potential for a variety of applications, including those in space exploration and medical technology. Sheng Xu, an Assistant Professor at Tohoku University's Frontier Research Institute for Interdisciplinary Sciences, emphasized the importance of the alloy's wide operational temperature range. "This alloy is the first of its kind to maintain superelasticity at such an extreme range of temperatures while remaining lightweight and strong, which opens up a variety of practical applications that were not possible before. The alloy's properties make it ideal for future space missions, such as creating superelastic tires for lunar rovers to navigate the extreme temperature fluctuations on the Moon's surface."

Super-adhesive patches can adapt to different motions for enhanced skin interaction

A research team affiliated with UNIST has unveiled an ultra-strong adhesive patch platform that adheres effectively to rough skin surfaces and shows remarkable motion adaptiveness during dynamic body movements, all while offering irritation-free removal on demand. The key to this technology lies in the surface adaptability inspired by barnacles and armadillo carapaces, which feature a tessellated structure that balances rigidity and flexibility. The team, led by Professor Hoon Eui Jeong from the Department of Mechanical Engineering and Professor Jae Joon Kim from the Department of Electrical Engineering at UNIST, along with researchers from the National Institute of Ecology (NIE), has introduced a highly adhesive, detachable, and stretchable skin patch, known as the Motion Adaptive Tessellation Patch.

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a smart, reusable adhesive more than ten times stronger than a gecko's feet adhesion, pointing the way for development of reusable superglue and grippers capable of holding heavy weights across rough and smooth surfaces. The NTU research team, led by Professor K Jimmy Hsia, found a way to maximise the adhesion of the smart adhesives by using shape-memory polymers, which can stick and detach easily when needed simply by heating them. Writing last month in the scientific journal National Science Review, the team details their breakthrough in adhesion by designing the shape-memory polymer material in the shape of hair-like fibrils.

Swift 4-D printing with shape-memory polymers

Shape-memory polymers or shape-shifting materials are smart materials that have gained significant attention within materials science and biomedical engineering in recent years to build smart structures and devices. Digital light processing is a vat photopolymerization–based method with significantly faster technology to print a complete layer in a single step to create smart materials. Fahad Alam and a team of scientists in electrical and computer engineering, and nuclear engineering at the King Abdullah University of Science and Technology, Saudi Arabia developed a facile and fast method to 3D print shape-memory polymer-based smart structures with a digital light printing 3D printer and custom resin. They combined a liquid crystal (a material that can change its shape with temperature) with resin, to introduce shape-memory properties to directly 3D print thermoresponsive structures—while avoiding the complexity of resin preparation. The team printed the structures with different geometries and measured the shape-memory response. The shape-memory polymers can be conveniently prepared for use as smart tools, toys, and meta-materials.

Advancing tissue engineering with shape memory hydrogels

One of the primary goals in the field of tissue engineering and regenerative medicine is the development of artificial scaffolds that can serve as substitutes for damaged tissue. These materials must ideally resemble natural tissue and must have the ability to support cell adhesion, proliferation, and differentiation. When considering scaffold materials, researchers account for the scaffold's properties, such as its surface roughness, its water content (hydration state), and its flexibility or stiffness (elastic modulus), since these properties are known to affect cell growth. Hydrogels are biocompatible cross-linked polymers with high water content and are a promising scaffolding material for soft tissue. They can be designed with different elasticities, which can match the mechanical properties of various natural tissues. However, their elastic modulus is linked to their composition, resulting in a difference in the characteristics between softer and harder hydrogels.

Classic PU Patent of the Month: The First SMPUs (1988)

Title: Shape memory polymer foam.  – and – Shape memory polyurethane elastomer molded article.

 Number/Link: EP0361418 and EP0361419

Applicant/Assignee: Mitsubishi Heavy Industries

Publication date: 27-09-1989

“Gist”: The first shape memory polyurethane foams and elastomers

Why it is interesting:Shape memory polymers are so-called “smart materials” that remain in a deformed shape until a trigger…