Background

The microstructure of a material is the very small-scale surface structures of the material, generally recognized to be structures revealed by an optical microscope of 25-x magnification or greater. The microstructure of any material can strongly influence its physical properties. If the microstructure is intentionally shaped for a particular function, many useful functionalities can be achieved. Examples include light-matter interaction, superhydrophobicity, self-cleaning ability, anti-bacterial properties, radiative and convective cooling control, and drag reduction.

The main currently available method of manufacturing micro- or nano-structures is by means of templates generated by the photolithographic process. However, the photolithographic process is prohibitively expensive and not scalable to produce the large surface areas needed for real-world applications.

One concrete example of a real-world application is reducing frictional drag on ships. According to the International Council on Clean Transportation, greenhouse gas (CO2) emissions by marine shipping amounted to 932 million tons or 2.6% of global CO2 emissions from fossil fuel in 2015 and are expected to increase continually with the economy of the developing countries. Because 70% to 80% of a ship’s propulsive power is used to overcome frictional drag, a technology that can reduce the friction would have a substantial global impact both economically and environmentally. Air lubrication systems, where injected air covers the bottom of the ship to reduce the friction, have been studied for decades. However, the air would spontaneously form bubbles and continue to be swept away from the hull surface. A correctly created functional microstructure on a ship’s hull would solve this problem of bubble sweeping and drastically reduce the energy consumption of global shipping.

This is only one example of the high utility of functional microstructures. Many other highly valuable applications exist for this technology and could be implemented if the cost of manufacturing functional microstructures was affordable. Therefore, a more affordable and scalable method of manufacturing functional microstructures would be highly desirable.

Technology Overview

NC State researchers, in collaboration with UCLA have developed a template-free, low manufacturing cost, and scalable method to create functional microstructures.

This technology obtains a “semi-regular” micro/nanostructure by utilizing the ribbing instability behavior in viscoelastic polymer under the shearing stress. Further, the texture periodicity and height in the polymer coat film can be adjusted through the roll coating process parameters and the polymer composite behavior.

The end result is a means of creating micro/nanostructures that overcomes the limitations of the photolithographic process, reduces manufacturing costs, and is highly scalable. This technology will allow for a substantial increase in functional microstructures, providing many functional benefits to manufactured goods.

Further Details

This technology is described in the paper titled: “Fabrication of Bioinspired Micro/Nano Textured Rough Surfaces Through the Scalable Roll Coating Process” (2022, https://asmedigitalcollection.asme.org/IMECE/proceedings/IMECE2021/85574/V003T03A003/1132560?casa\_token=nb8oQPR5lWYAAAAA:x0KmwPjt4lgg7vG3GyBmiM7sueqaKewKTe-hYdmfVX7iL2qQsVUckmx0pyC9tveb5wrp0Anm)

Benefits

Low cost manufacturing of microstrucutures
Scalable manufacturing of microstructures
Improved functionality of manufactured goods

Applications

Creation of functional microstructures.

Affordable and Scalable Manufacturing of Functional Microstructures

Patents

IP Status