MIT Serves Up Surfaces on Demand

FRIDAY, JUNE 12, 2015

CAMBRIDGE, MA--Given a squeeze, ship hulls could self-clean, camouflage could transform itself, and surface friction could adjust with a new printable material now in development.

Massachusetts Institute of Technology researchers have developed a soft material that can change topographies at will—from smooth to bumpy, or some combination, and back again.

The work could lead to a new class of materials with dynamically controllable and reversible surface properties, according to a research announcement from MIT.

The research ("Locally and Dynamically Controllable Surface Topography Through the Use of Particle-Enhanced Soft Composites") was published recently in the journal Advanced Functional Materials.

Tunable, Reversible

The work is a first, say researchers Mark Guttag and Mary C. Boyce. Guttag is an MIT doctoral student in mechanical engineering; Boyce, formerly of MIT, is now dean of engineering at Columbia University.

“There are no previous techniques that provide comparable flexibility for creating dynamically and locally tunable and reversible surface changes,” Guttag and Boyce reported.

Although the material could respond to a variety of stimuli—such as temperature, humidity or an electronic charge—the MIT research focused on the application of physical pressure.

“Depending on the arrangement of the particles, using the same amount of compression, you can get different surface topographies, including ridges and bumps, along the surface,” said Guttag.

The technology could be used to develop fouling-resistant hulls or to guide microfluids, develop camouflage, or change the aerodynamics of an object, the team says.

How It Works

The material is composed of two polymers with different degrees of stiffness, MIT explained. Rigid particles are embedded in a matrix of a more flexible polymer.

Felice Frankel / MIT

Polymer material produced by a 3-D printer includes soft, flexible material (clear or lighter tone) with particles of hard material (black) embedded in predetermined arrangements. When the material is compressed, its surface become bumpy in a pattern determined by the hard particles.

When squeezed, the material’s smooth surface changes to a pattern determined by the spacing and shapes of the implanted harder particles; when released, it reverts to the original form.

The system can produce simple, repetitive patterns of bumps or creases, which could be useful for changing an object's reflectivity or aerodynamic resistance.

Or hard particles could be arranged to produce highly complex surface textures that, for example, create microfluidic channels to control the movement of liquids inside a chemical or biological detector, Guttag says.

Changeable and irregular textures could also benefit drag reduction and camouflage, the team said. For example, embedding elongated particles could create asymmetrical surface textures that have high friction in one direction but are slippery in another.

'Geometry Driven'

Guttag said the material could be easily resized with the same results because the system is “all geometry driven.”

The same design principles could be used to modify materials using other stimuli, such as through application of an electric charge, or by changing temperature or humidity, Guttag adds.

The system was originally developed using computer simulations, which were then validated by 3-D-printed versions of several of the designs. The patterns produced when the materials were squeezed closely matched those of the simulation, Guttag said.

MIT and the Masdar Institute of Science in the United Arab Emirates provided funding for the project.


Tagged categories: Antifoulants; Coating Materials; Coatings Technology; Marine; North America; Polymers; Research

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