Despite the fact that shape memory materials have a very good potential for use in a wide variety of applications, many of them have one feature: in order to change their shape, they require heat. This, in turn, can be a problem for their use in temperature-sensitive environments, such as the human body. However, the new development of Swiss scientists does not have this drawback, since instead of heat, the material with shape memory created by them uses a magnetically sensitive liquid. Development is reported in Advanced Materials magazine.
How does shape memory material work?
Developed by scientists from the Swiss Paul Scherrer Institute and the Swiss Higher Technical School of Zurich, the material is based on a silicone-containing polymer with drops of a special liquid encapsulated inside it. This "magnetorheological fluid" in turn consists of water, glycerin, and tiny particles of carbonyl iron. The composition of the liquid is similar to milk, in which fat particles are dispersed (dissolved) in an aqueous solution.
In its normal state, the structure of the material remains soft and flexible. But one has only to influence it with a magnetic field, and the drops of the liquid contained in it lengthen, and the iron particles in it line up along the source of the magnetic field. Thanks to these two factors, a 30-fold increase in material stiffness is observed.
In practice, this means that if you set the initial shape for a material, and then act on it with a magnetic field, then it solidifies and retains this shape until the effect of the magnetic field stops. Once this happens, the material returns to its original shape and becomes soft.
In previous studies, scientists have already created magnetically activated shape memory materials, consisting of polymers containing metal particles. According to the Swiss scientists, the peculiarity of their magnetorheological fluid allows their polymer to become more rigid.
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Scientists are voicing several potential use cases for their new material. For example, it can be used to make medical catheters capable of changing their rigidity after being safely inserted into the blood vessels. It can be used to create self-healing tires for ground-based research spacecraft, or to be used in the manufacture of robotics components that can move without the need for motors.
Nikolay Khizhnyak
