Just a single drop of acid can make aluminum transparent, allowing over 70% of visible light to pass through (see photo).

Most people likely do not think about transparent materials when using their gadgets. However, the touch screen of our phones, the protective glass on solar panels, and many optical components in cameras are based on transparent metal oxides. Traditional methods for producing such materials are often costly, but now scientists have developed a completely new technique that could be groundbreaking, according to Study Finds.

In a new study, a team from the Nara Institute of Science and Technology in Japan and Ateneo de Manila University in the Philippines devised a novel method for converting aluminum into transparent aluminum oxide. The authors of the research note that this transformation requires only a drop of acid and low voltage — this new approach boasts simplicity and environmental benefits.

Instead of immersing entire aluminum sheets in acid baths, as traditional methods require, the scientists propose using a single microdrop of sulfuric acid solution, strategically placed on the surface of the aluminum. When a low voltage (just 2 volts) was applied for 10 minutes, the aluminum beneath the drop transformed into a very transparent round spot.

The resulting transparent material transmits more than 70% of visible light while blocking part of the near-infrared light, making it potentially valuable for use in electronics, solar panels, optical sensors, and energy-efficient windows.

This "drop-scale anodization" technology creates high-precision transparent spots with smoother surfaces than conventional methods and can be extended to other metals to produce various transparent metal oxides with minimal environmental impact. The authors of the study believe that their new drop-scale anodization technique could eventually be applied to other transparent metal oxides.

Anodization is an electrochemical process that converts a metal surface into a durable, corrosion-resistant oxide layer. While anodization has been used for several decades, this research presents a new approach that miniaturizes the reaction zone to a single drop.

The researchers examined the transformation under a microscope and discovered something intriguing: aluminum did not become transparent immediately. Instead, the material began to change at the edges of the acid drop, with transparency slowly penetrating inward. As a result, the scientists obtained a perfect round transparent spot and realized they could control its size and quality by adjusting the voltage and duration of the process.

This approach offers significant advantages over traditional methods: instead of masking protected areas with special coatings, the drop itself creates a natural boundary for the reaction. The authors of the study assert that, in addition to sharply reducing chemical waste, this technology produces a superior product. Firstly, the new drop method allows for smoother and more uniform areas; secondly, the method significantly decreases environmental impact; thirdly, the scientists can regulate the quality and size of the material.

According to the researchers, another advantage is that the approach requires only a basic power source, platinum wire, and diluted acid, which are available in most modest laboratories.