Semiconductor quantum dots are used in a number of applications, including light-emitting devices, displays and sensors, thanks to their properties of tunable fluorescence wavelength, narrow bandwidth and high brightness. Most of those applications require the dots to be very precisely patterned with targeted properties on solid substrates. Unfortunately, typical direct-write printing methods such as inkjet and gravure printing are limited in their resolution and structural complexity, as well as requiring a lot of post-processing time.
A group of researchers led by Professor Yuebing Zheng from the University of Texas at Austin has developed a new method of quantum dot patterning, and it’s similar to 3D printing. It even has a great name – it’s called bubble printing.
“Bubble printing technique is a direct-print technique which uses a microbubble generated using low-power laser beam to pattern nanoparticles on a substrate,” University of Texas at Austin graduate student Bharath Rajeeva tells 3DPrint.com. “This is similar to 3D printing, wherein the patterns are defined based on the movement of a either a laser beam/nozzle. However, our bubble printing technique is focused on gaining higher resolution and fabricating patterns at the nano/micro scale.”
The research was published in a new paper entitled “High-Resolution Bubble Printing of Quantum Dots,” which you can access here. The bubble printing technique allows for quantum dots to be precisely patterned on plasmonic substrates with submicron resolution of greater than 700 nm linewidth and strong adhesion. It also allows for the dots to be printed on flexible substrates and can be integrated with smartphones to realize haptic integration.
The technique works by using a single low-powered laser beam to generate a sub-micron-sized bubble at the interface of a colloidal suspension of nanoparticles and a plasmonic substrate containing a network of metallic nanoparticles. The bubble captures and freezes the nanoparticles on the substrate, and different patterns can be created depending on the movement of the stage. By using a smartphone, free-form macroscale movements can be created and replicated at the nanoscale.
The advantages of the technique are many. Specialized inks are not required, and issues such as nozzle clogging, ink spreading, and excessive post processing time don’t exist. The technique also opens doors to many applications, as well.
“We have demonstrated anti-counterfeiting application via fabrication of micro-scale QR code (80 µm×80 µm),” the researchers state. “The generality and simplicity of bubble printing along with its flexible substrate compatibility enables the fabrication of multiple functional devices such as ultra-high resolution displays, multi-sensor integration at nano/micro scale, and nanolasers. In addition, the haptic-integration can advance research and education in nanoscience and nanotechnology.”
Further work will research other nanoparticle systems for applications such as colloidal nanosensors, flexible LED microdisplay devices, and colloidal waveguides. Additional applications could include flexible electronics, flexible photonics and even biological applications. The key challenges to be overcome at the moment are improving the roughness of the lines and maintaining the bubble stability over centimeter-scale areas.
“The scientific core of our finding is the stable bubble-mediated immobilization at the submicron scale, and the ability to maintain the submicron-sized bubble’s stability over a large area,” the researchers explain. “Our work circumvents the barrier of achieving a widely applicable, high-throughput and user-friendly printing technique in the submicrometer regime, along with simultaneous fluorescence modification capability.”
Authors of the research paper include Bharath Bangalore Rajeeva, Linhan Lin, Evan P. Perillo, Xiaolei Peng, William W. Yu, Andrew K. Dunn, and Yuebing Zheng. Discuss in the Bubble Printing forum at 3DPB.com.