This Method can produce strong, lightweight materials with specific surface properties.
It is created a new technology of manufacturing micro structured surfaces that have novel three-dimensional textures. These surfaces, made by self-assembly of carbon nanotubes, could exhibit a variety of useful properties including controllable mechanical stiffness and strength, or the ability to repel water in a certain direction.
We have established that mechanical forces can be used to direct nanostructures to form complex three-dimensional microstructures, and that we can independently control.
The technique works by inducing carbon nanotubes to bend as they grow. The mechanism is analogous to the bending of a bimetallic strip, used as the control in old thermostats, as it warms: One material expands faster than another bonded to it. But in this new process, the material bends as it is produced by a chemical reaction.
The process begins by printing two patterns onto a substrate: One is a catalyst of carbon nanotubes; the second material modifies the growth rate of the nanotubes. By offsetting the two patterns, it showed that the nanotubes bend into predictable shapes as they extend.
We can specify these simple two-dimensional instructions, and cause the nanotubes to form complex shapes in three dimensions, where nanotubes growing at different rates are adjacent, “they push and pull on each other,” and producing more complex forms. It is a new principle of using mechanics to control the growth of a nanostructured material.
Few high-throughput manufacturing processes can achieve such flexibility in creating three-dimensional structures, This technique, he adds, is attractive because it can be used to create large expanses of the structures simultaneously; the shape of each structure can be specified by designing the starting pattern. This technique could also enable control of other properties, such as electrical and thermal conductivity and chemical reactivity, by attaching various coatings to the carbon nanotubes after they grow.
It can be coat the structures after the growth process you can exquisitely modify their properties. For example, coating the nanotubes with ceramic, using a method called atomic layer deposition, allows the mechanical properties of the structures to be controlled. When a thick coating is deposited, we have a surface with exceptional stiffness, strength, and toughness relative to density, when a thin coating is deposited the structures are very flexible and resilient.
This approach may also enable “high-fidelity replication of the intricate structures found on the skins of certain plants and animals,” it is possible to mass-produce surfaces with specialized characteristics, such as the water-repellent and adhesive ability of some insects.
This is the surfaces have the durability of carbon nanotubes, which could allow them to survive in harsh environments, and could be connected to electronics and function as sensors of mechanical or chemical signals.