New Shapeshifting 3-D Material Could Make for Better Stents

Harvard University researchers developed a new, flexible, versatile material, which can be fine tuned to change its size and shape to adapt to different environments.

Kristopher Sturgis

via GIPHY

The new material is a structure made of thin walls that can be folded, molded, and reshaped. The result is objects whose size, volume, and shape can be altered to form any number of architectural structures or objects.\

Harvard researchers and engineers created the material with a composition that can be continuously reshaped and controlled, and can even be embedded with a programmed actuator so that it can take shape on its own.

The group's work could represent a new class of versatile, bendable materials that can vary in size from the nanoscale to the meter-scale--making the material useful in a variety of different ways from portable architectural structures to surgical stents. Johannes T.B. Overvelde, a graduate student from Harvard and first author on the paper describing the work, says that origami principles inspired the design. The structure is is made from extruded cubes with 24 faces and 36 edges.

"Like origami, the cube can be folded along its edges to change shape," Overvelde says. "In our paper, we demonstrate (both theoretically and experimentally with a centimeter-scale prototype) that the cube can be deformed into many different shapes by folding certain edges, which act like hinges. We furthermore embedded pneumatic actuators (air pockets) into the structure, which can be programmed to deform specific hinges--changing the cube's shape and size, and removing the need for external force."

These pneumatic actuators are what enable the cubed device to fold its edges, altering its size and shape on its own. Overvelde says the material can be fitted with any kind of actuator, including electric, thermal, and even water mechanisms. WIth similar technologies relying on standard mechanics, this new material offers the unique ability to self integrate its surface and shape to form a desired structure, including potential medical applications.

"I certainly think the metamaterial can be used to build medical stents," Overvelde said. "Depending on the design, the volume and shape of the metamaterial, it can be changed considerably. Another interesting feature could be to include heat actuation in the stent, so that it automatically deploys when bringing it into contact with an environment that is above room temperature."

The latest prototype is a cube comprised of 64 connected individual cells that can grow, shrink, bend, and fold to form different shapes with varying degrees of stiffness. Enacting these actuated changes in material properties actually adds a fourth dimension to the material, enabling users to simply know what they need to actuate in order to get the material to form the desired shape.

"By using various types of actuation, this material can be programmed to interact with its environment in different ways as it changes shape," Overvelde says. "If one were to make a wall from this material, for example, it could be folded in different ways to manipulate sound or light. Or it could be used to form a roof that autonomously opens on a hot day to allow fresh air to come in, or close when it starts to rain." 

Overvelde says the material could even be used in the arena of drug delivery, in which the shape of the metamaterial can change over time to increase or decrease the exposed surface area. For now, the group is focused on exploring all the different possibilities for this uniquely versatile material.

"This structural system has fascinating implications for dynamic architecture," Overvelde says. "Depending on the characteristic size of the structure, it could be applied today in many ways. The main challenges lie in reducing the size of the structure down to the micro or even nano-scale. We are currently working on generalization of the extruded cube design, to create a database of metamaterials, all with their own unique properties."

Kristopher Sturgis is a contributor to Qmed and MPMN.

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