Using microbubbles, the technique allows researchers to quickly, gently and precisely handle the tiny particles to more easily build tiny machines, biomedical sensors, optical computers, solar panels and other devices. This advanced control is key to harnessing the properties of the nanoparticles.
Using their bubble-pen device, the researchers focus a laser underneath a sheet of gold nanoislands to generate a hotspot that creates a microbubble out of vaporised water. The bubble attracts and captures a nanoparticle through a combination of gas pressure, thermal and surface tension, surface adhesion and convection. The laser then steers the microbubble to move the nanoparticle to a site on the surface. When the laser is turned off, the microbubble disappears, leaving the particle on the surface. 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," assistant professor, Yuebing Zheng said. "The capability of arranging the particles will help to advance a class of materials, known as metamaterials, with properties and functions that do not exist in current natural materials."
According to Prof Zheng, bubble-pen lithography can leverage a design software program in the same way as a 3D printer, so it can deposit nanoparticles in real time in a pre-programmed pattern or design. The researchers were able to write the UT Austin Longhorn symbol and create a dome shape out of nanoparticle beads.
In comparison to other existing lithography methods, bubble-pen lithography has several advantages, Prof 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.
Prof Zheng 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.