AMP_06_September_2021

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 1 1 1 PROCESS TECHNOLOGY RAPID CRYSTALLIZATION Researchers from Fudan Univer- sity and Peking University, both based in China, along with other collabora- tors including the Institute of Industrial Science at The University of Tokyo, con- ducted experimental and computation- al studies on fast crystal growth under deep supercooling. Their work provides critical insight into the mechanism of fast crystal growth at ultra-low tempera- tures, contributing to many technologi- cal applications by enhancing glass sta- bility or producing high quality crystals. A key to fast crystal growth revealed by simulations and experiments is that the solid-liquid interfaces in the super- cooled liquids are thick and rough. The large contact area between ordered is- lands and the surrounding disordered liquid helps break up the disorder and facilitates rapid crystal growth. “Another key result is that the dis- ordered state is inherently unstable mechanically, leading to a domino-like chain reaction of crystal growth,” ex- plain the researchers. “This is facilitat- ed by the ability of the newly formed, imperfectly ordered regions of the crys- tal to reorder and in so doing prevent accumulation of disorder.” They sug- gest there is potential to create ultra- stable glasses and nearly perfect crys- tals. www.iis.u-tokyo.ac.jp/en. ONE-STEP PRINTED CIRCUITS A new printing method devel- oped by scientists at The Chinese Uni- versity of Hong Kong makes fabricat- ing integrated circuits and other tiny devices easier and cheaper. The ap- proach overcomes issues in conven- tional micromanufacturing processes, which require multiple steps, advanced equipment, highly trained personnel, and are prone to errors. The method, called light-induced material deposi- tion, starts with depositing a mixture of two solutions onto a surface—one con- taining metal particles and the other containing semiconductor nanoparti- cles. The scientists found their process works on a wide range of surfaces, in- cluding glass, quartz, sapphire, indium tin oxide, and tape. The metal particles in the first solution can be gold, plati- num, silver, iron, zinc, or nickel. Also, a wide range of nanoparticles can be used for the second solution. A series of tests confirmed the quality of the deposited materials and their electrical and mechanical proper- ties. The scientists used the method to print a variety of structures, including a resistor flex sensor commonly used in robotics. The approach is cheap, ver- satile, and easy to use; so much so that it would be possible to print electrical circuits in the field. It could also make repairing electrical circuits easier than existing approaches. The scientists are now trying to improve the process so it can print even smaller structures, down to 20 nanometers in size. “We will also try to further simplify the setup and make a market-ready prototype, with the aim of commercializing our product within five years,” the researchers say. www.cuhk.edu.hk/english. Graphic of the domino-like crystallization of glass. Courtesy of University of Tokyo. Scientists at the Salk Institute, La Jolla, Calif., transformed tobacco and corn husks into silicon carbide and quantified the process with more detail than ever before. Also known as carborundum, SiC is an ultrahard material used in ceramics, sandpaper, semiconductors, and LEDs. Next, the team hopes to explore the new process with silicon-containing plants like horsetail and bamboo. salk.edu. BRIEF Using light-induced material deposition, the panda printed in platinum and gold (top) was made to match the design (bottom). Courtesy of The Chinese University of Hong Kong.