New alloys and embedded nanostructures for durable, color-neutral antimicrobial touchscreens

Touchscreens are everywhere in our daily life, from smartphones and tablets to ATMs, but they also act as reservoirs for harmful microorganisms and hotspots for infectious diseases transmission. There is an increasing demand for antimicrobial transparent surfaces and coatings that inhibit the microbial growth on touchable screens.

While copper is a well-known antimicrobial agent, its implementation in interactive displays has been hindered by its distinctive reddish color, opaqueness, and its susceptibility to being worn away by constant physical contact if integrated directly on the device surface. Its good electrical conduction is also a limitation for its implementation in touch-enabled devices, as they required complete insulation to preserve its touch sensitivity.

Now, in two recently published studies in Scientific Reports and APL Materials, a team of researchers from ICFO has reported two new approaches to overcome these challenges.

Copper-Zinc alloy for color neutrality

The first approach has been reported in an article published in Scientific Reports by ICFO researchers Alessia Mezzadrelli, Rubaiya Hussain and ICREA Professor at ICFO Valerio Pruneri in collaboration with researchers Wageesha Senaratne and Prantik Mazumder. The study introduced the use of a copper-zinc (Cu–Zn) alloy instead of pure copper as antimicrobial agent for developing transparent and color-neutral glass surfaces tailored for its use in touchscreen display applications.

While previous research on nanostructured copper achieved high antimicrobial efficacy figures, it often resulted in a slight reddish tint that affected the transparency of the screen. By mixing copper with zinc, the researchers successfully "dampened" the intrinsic copper color offering a significantly improved chromatic neutrality.

In their work, the researchers deposited nanostructured copper–zinc (Cu–Zn) ultra-thin film on existing glass surface samples and processed using a simple, scalable, and lithography-free technique.

The resulting optimized surface samples achieved a high level of transparency, with an average visible light transmission exceeding 80%, and a true color neutrality (no color tint), that is a color difference (ΔE) of 2.77, meeting the required industry standards for displays.

The researchers tested also the antimicrobial performance of the surface samples. The biological testing confirmed that the coating showed rapid and high bactericidal efficacy with a 99.9% reduction of bacteria like Staphylococcus Aureus and Escherichia Coli.

“These findings open the path to have a scalable and effective solution for next-generation high hygienic interactive display technologies based on Cu-Zn, also thanks to the lithography-free fabrication process”, said Alessia Mezzadrelli, early stage researcher (ESR) of the Nano-Glass project at ICFO and first author of the study.

Copper nanodisks shielded in nanoholes

In a second study published in APL Materials, the ICFO researchers Iliyan Karadzhov, Rubaiya Hussain, Alessia Mezzadrelli, and ICREA Prof. Valerio Pruneri at ICFO collaborated with researchers Wageesha Senaratne and Prantik Mazumder to develop a transparent and robust glass surface designed to keep antimicrobial copper working even after repeated finger swipes and cleaning. The key idea is to place the antimicrobial material just below the surface “wear plane”, where it is protected from abrasion while still able to release ions that can kill bacteria.

Using a scalable, lithography-free six-step process compatible with wafer-scale manufacturing, the team created millions of nanoholes (around 80-100 nm deep) in  glass samples  and deposited copper nanodisks at the bottom of each hole. The engineered surface acts like a protective armor: swipes from fingers or cleaning cloths pass over the top, while the copper remains sheltered underneath.

In abrasion tests simulating thousands of swipes, the embedded copper remained intact, with no loss of optical or antimicrobial performance. The surfaces showed 80%–85% average transmission in the visible range and only minimal color shift compared to uncoated glass. In lab tests, the surfaces also achieved a 99% reduction of E. coli after one hour of contact.

“These results demonstrate a scalable route to mechanically durable, optically clear antimicrobial surfaces for touch-based devices and everyday transparent materials,” said Iliyan Karadzhov, first author of the study and NANO-GLASS project ESR.

Both studies rely on thermal dewetting, in which a thin metal film breaks into nanoscale structures when heated, enabling complex designs without expensive lithography. “With these two studies, we have shown that it is possible to enhance the antimicrobial performance and durability of touch-enabled display surfaces using cost-effective approaches”, said Valerio Pruneri, ICREA Professor at ICFO and NANO-GLASS project coordinator.

Original Papers:

• Mezzadrelli, A., Hussain, R., Senaratne, W., et al. (2025). Color-neutral, transparent, antimicrobial glass surface based on nanostructured Cu–Zn. Scientific Reports, 15, 43298. https://doi.org/10.1038/s41598-025-27050-5
• Karadzhov, I., Hussain, R., Mezzadrelli, A., Senaratne, W., Mazumder, P., & Pruneri, V. (2025). Lithography-free fabrication of transparent, durable surfaces with embedded functional materials in glass nanoholes. APL Materials, 13(12), 121112. https://doi.org/10.1063/5.0304861