Advancing the discovery of new shape-shifting materials
Futuristic smart materials that are soft and capable of changing shape in response to light or heat could be used in situations where accessibility might be an issue such as in space, on the ocean floor or even inside the human body.
Unlike conventional liquids, liquid crystals are anisotropic meaning that their material properties (for example, their refractive index), vary when measured in different directions. Liquid crystals are perhaps best known for their application in LCD TVs, where the orientation of the molecules that make up the liquid crystal can be manipulated via the application of an electric field. This allows them to control the passage of light, creating the images that we see on screen.
Liquid crystal elastomers (LCEs) are materials that combine the reversible ordering properties of liquid crystal molecules, with the elasticity of a cross-linked polymer network, which means they can bounce back into shape when an external stimulus is removed.
Due to their elasticity and softness compared to shape-shifting metal alloys, LCE materials are ideally suited for use as actuators in medical and soft robotics applications, where they react to environmental changes. For example, they might change their shape in response to an increase or decrease in light or heat, before reverting to their original molecular state when the external stimuli is removed.
Some of the earliest examples of LCE materials were used in optical components. For example, a European patent filed in 1988 by Ludwig Pohl, one of the founding fathers of liquid crystal research, Bernard Rieger and Heino Finkelmann, describes several uses for liquid crystalline polymers in optical components such as polarisers.
Heino Finkelmann also contributed to a further paper in 2002 which proposed the use of photoreactive liquid single crystal hydrogels in an innovative concept for a bi-focal contact lens. More recently, research into LCE materials has focussed on their response to changes in light or temperature, elongating when cooled below the LC-isotropic phase transition temperature of the material and subsequently contracting when the material is heated back up. These properties make LCEs ideally suited as actuators for artificial muscles and prosthetic limbs.
In February 2024, researchers at California-based Lawrence Livermore National Laboratory, in collaboration with several US academic institutions, also published a paper describing how 3D-printed LCE composite materials, created with photo-responsive inks, could be made to change shape as a result of localised exposure to a 808nm laser. These shape-shifting smart materials could be particularly useful in areas where it is not possible to use actuators that rely on an electrical current, such as in space or in subsea engineering.
LCE materials remain a key area of innovation and could potentially be the source of many as yet undiscovered benefits, which could find use in many different applications. When preparing patent applications, innovators should bear in mind potential alternative uses of the LCE innovation to avoid unnecessarily limiting the scope of its commercial protection.
For innovators exploring medical applications specifically, it is also important to bear in mind that whilst methods of treatment or therapy aren’t patentable due to exclusions that exist in UK and European patent law, an innovative ‘medical device’ can usually be protected.
The discovery of new shape-shifting materials is advancing quickly and promises to bring lasting benefits for our health at the same time as improving our understanding of the world around us.
Gemma McGeough, partner, and Alex Harvey, senior associate, are patent attorneys at European intellectual property firm, Withers & Rogers. Both specialise in the field of engineering materials.
