'Magnetic Hair' Directs Fluid & Light, Has Applications in Waterproof Smart Windows

MIT engineers have developed a new elastic material coated with microscopic, hair-like structures that tilt in response to a magnetic field. Depending on the field's orientation, the nickel microhairs can tilt to form a path through which fluid can flow. The material can even direct water upward, against gravity. Each microhair is about one-fourth the diameter of a human hair. The researchers fabricated an array of the microhairs onto an elastic, transparent layer of silicone. In experiments, the magnetically activated material directed the flow of light much as window blinds tilt to filter the sun. Researchers say the work could lead to waterproofing and anti-glare applications, such as smart windows for buildings and cars.

Transcript

00:00:05 Researchers at MIT have developed a flexible material inspired by animal hair that moves in response to a magnetic field. The surface consists of a thin, flexible polymer skin and a ferromagnetic hair-like micropillar array. The orientation of these micropillars can be controlled by an external magnetic field. The micropillars tilt in the direction of the magnetic field and as a result the pillars can control the direction in which fluids spreads through the material. When the magnetic field switches direction the fluid instantaneously changes direction following the orientation of the field. Even on a vertically inclined surface fluid can be

00:00:44 tuned to climb against gravity. The material can also influence a fluids drag. Under a more tilted magnetic field a droplets drag across the material is reduced. In addition to manipulating the flow of fluids the materials tilting pillars can also influence optical patterns similar to the way window blinds filter sunlight. The researchers say this work provides exciting opportunities for real-time fluid and light manipulation. The surface can serve as an important platform for applications such as smart windows, versatile artificial skin, cell manipulation, dynamic optical devices and fluid control.