Researchers from the Paul Scherrer Institute PSI and ETH Zurich have developed a new material which holds shape when it is placed in a magnetic field. It is a composite material consisting of two components. Unlike the previous materials with shape memory, it is composed of polymer and drops of the so-called magnetorheological fluid. Applications of this new type composite materials include medicine, aerospace, electronics and robotics. Currently, the researchers publish their results in the scientific journal Advanced Materials .
It’s like a magic trick: the magnet moves away from the black twisted strips, and the strip is relaxed without any additional effect. What looks like magic to explain magnetism. Black the tape consists of two components: polymer based on silicone, and small drops of water and glycerin, in which float particles are carbonyl iron. The latter provide the magnetic properties of the material and memory of its form . If a composite material with tweezers force takes shape, and then is subjected to a magnetic field , it retains its shape even after removal of the forceps. Only when the magnetic field is also removed, the material returns to its original shape.
Still comparable materials consisted of polymer with embedded metal particles. Instead, researchers from PSI and ETH Zurich have used drops of water and glycerin to insert the magnetic particles in the polymer. Thus, they created a variance similar to that found in milk. In milk, small fat droplets finely dispersed in an aqueous solution. They are essentially responsible for the white color.
Similarly, a drop of magnetorheological fluid finely distributed in the new material. “Since magneto-sensitive phase, dispersed in the polymer, is a liquid, the forces arising from the application of a magnetic field, much more than previously reported,” explains Laura Heyderman, head of the mesoscopic systems group at PSI and Professor at ETH Zurich. If the magnetic field acts on the composite material, it becomes rigid. “This new material concept can only come through joint work groups with expertise in two different fields – magnetic and soft materials,” says Hagerman.
Shape memory via the alignment with the magnetic field
The researchers studied the new material with the help of the Swiss light source SLS at PSI, among others. Using x-ray tomographic images obtained using this light source, they found that the length of the droplets in the polymer is increased under the influence of a magnetic field and that of the carbonyl iron particles in the fluid are aligned at least partially along the magnetic field lines , These two factors increase the stiffness of the material under test by 30 times.
The fact that the shape memory material activates the new magnetic fields, offers additional benefits in addition to a higher power. Most of the material with memory shape responsive to temperature change. In medical applications, two problems arise. First, the excessive heat damages the body’s own cells. Second, it is not always possible to guarantee uniform heating of an object that remembers its shape. Both disadvantages can be avoided by including a shape memory using a magnetic field.
Mechanically active materials for medicine and robotics
“With our new composite material, we have taken another important step towards the simplification of components in a wide variety of applications, such as medicine and robotics,” says ETH Zurich and researcher at the PSI materials Paolo the Test, first author of the study. “Therefore, our work provides a starting point for a new class of mechanically active materials”.
Numerous applications in medicine, space flight, electronics and robotics possible for materials with shape memory. For example, catheters that change rigidity when pushed through the blood vessels to the site of surgery during minimally invasive operations. In space materials with shape memory demand on tires for all-terrain vehicles, which is inflated or re-develop. Electronics soft functional materials can be used in flexible power or data cables in wearable devices and robots that can perform a mechanical movement without engine.
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