Filipino scientists make aluminum transparent by using tiny acid droplets

Transparent aluminum oxide (TAlOx), a real material despite its sci-fi name, is incredibly hard and resistant to scratches, making it perfect for protective coatings on electronics, optical sensors, and solar panels. On the sci-fi show Star Trek, it is even used for starship windows and spacefaring aquariums. 

Current methods of making TAlOx are expensive and complicated, requiring high-powered lasers, vacuum chambers, or large vats of dangerous acids. That may change thanks to research co-authored by Filipino scientists from the Ateneo de Manila University. 

Instead of immersing entire sheets of metal into acidic solutions, the researchers applied microdroplets of acidic solution onto small aluminum surfaces and applied an electric current. Just two volts of electricity—barely more than what’s found in a single AA household flashlight battery—was all that was needed to transform the metal into glass-like TAlOx.

This process, called “droplet-scale anodization,” is not only simpler than existing manufacturing methods but also environmentally friendly, cutting down on chemical waste and energy use. The technique relies on a special effect called “electrowetting,” where an electric field changes the properties of a liquid droplet, allowing precise control over the anodization process.  

This new approach might make TAlOx cheaper and more accessible for applications in everything from touchscreens and lenses to ultra-durable coatings for vehicles and buildings. It could also lead to advances in miniaturized electronics, as scientists now have a way to convert metal surfaces into insulating, transparent layers on a microscopic scale.  

The breakthrough was published in the journal Langmuir by Marco Laurence M. Budlayan and Raphael A. Guerrero from the Ateneo de Manila University School of Science and Engineering’s Department of Physics; and Juan Paolo S. Bermundo, James C. Solano, Mark D. Ilasin, and Yukiharu Uraoka from the Nara Institute of Science and Technology Division of Materials Science’s Information Device Science Laboratory in Japan.