Scientists have developed a new 'bubble-pen' that uses microbubbles to inscribe nanoparticles on a surface, an invention that could help in the manufacturing of many devices like tiny machines, optical computers and solar panels. Working with nanoparticles while keeping their properties and functions intact can be difficult. 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. Researchers at the Cockrell School of Engineering at the University of Texas at Austin have 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 particles in various shapes, sizes, compositions and distances between nanostructures. Using the bubble-pen device, the researchers focus a laser underneath a sheet of gold nanoislands (nanoscale islands) to generate a hotspot that creates a microbubble out of vapourised 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 on 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 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," said Yuebing Zheng, who led the study. The technique could be especially helpful for science and medicine because researchers would be able to precisely control cells, biological material, bacteria or viruses for study and testing, Zheng added. Moreover, bubble-pen lithography can leverage a design software programme in the same way as a 3D printer, so it can deposit nanoparticles in real time in a pre-programmed pattern or design. The technique can be used to test prototypes and ideas for devices and materials more quickly. It also has the potential for large-scale, low-cost manufacturing of nanomaterials and devices. The research was published in the journal Nano Letters.