Researchers in the Cockrell School of Engineering at The University of Texas at Austin (UT Austin) have developed a new, efficient method for creating nanomaterials. Termed bubble-pen lithography, this new method relies on microbubbles to inscribe, or write, nanoparticles onto a surface.

Researchers' interest in nanoparticles, which are 1–100nm in size, has grown rapidly because of their versatility and strength. Some nanoparticles have optical properties that are useful for electronics, while others have the ability to absorb solar energy. In biomedical applications, nanoparticles can serve as drug carriers or imaging agents.

But working with these particles while keeping their properties and functions intact can be difficult. And existing lithography methods, which are used to etch or pattern materials on a substrate, are not capable of fixing nanoparticles to a specific location with precise and arbitrary control.

A research team led by assistant professor Yuebing Zheng has now invented a way to handle these small particles and lock them into position without damaging them. Using microbubbles to gently transport the particles, the bubble-pen lithography technique can quickly arrange nanoparticles in various shapes, sizes, compositions and distances between nanostructures. This advanced control is key to harnessing the nanoparticles’ properties. The team, which includes Cockrell School associate professor Deji Akinwande and professor Andrew Dunn, describe their patented device and technique in a paper in Nano Letters.

The bubble-pen device utilizes a laser to focus a beam of light underneath a sheet covered in gold nanoparticles. This beam generates a hotspot on top of the sheet, which in turn generates a microbubble of vaporized water that attracts and captures a nanoparticle through a combination of gas pressure, thermal and surface tension, surface adhesion and convection.

The laser beam can then move the microbubble, together with the captured nanoparticle, to a specific position on the surface. When the laser is turned off, the microbubble disappears, leaving the particle in the required position. If necessary, the researchers can expand or reduce the size of the microbubble by increasing or decreasing the laser beam's power.

"The ability to control a single nanoparticle and fix it to a substrate without damaging it could open up great opportunities for the creation of new materials and devices."Yuebing Zheng, UT Austin

"The ability to control a single nanoparticle and fix it to a substrate without damaging it could open up great opportunities for the creation of new materials and devices," Zheng said. "The capability of arranging the particles will help to advance a class of new materials, known as metamaterials, with properties and functions that do not exist in current natural materials." The technique may also have biological and medical applications, because as well as nanoparticles it could precisely control the position of cells, biological material, bacteria or viruses for study and testing, Zheng added.

Moreover, bubble-pen lithography can implement design software in the same way as a 3D printer, allowing it to deposit nanoparticles in real time in a pre-programmed pattern. In this way, the researchers were able to write the UT Austin Longhorn symbol and create a dome shape out of nanoparticle beads.

In comparison to other lithography methods, bubble-pen lithography has several advantages, Zheng says. First, the technique can be used to test prototypes and ideas for devices and materials more quickly. Second, the technique has the potential for large-scale, low-cost manufacturing of nanomaterials and devices. Other lithography techniques require more resources and a clean room environment.

Zheng says he hopes to advance bubble-pen lithography by developing a multiple-beam processing technique for industrial-level production of nanomaterials and nanodevices. He is also planning to develop a portable version of the technique that works like a mobile phone for use in prototyping and disease diagnosis.

This story is adapted from material from UT Austin, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.