Antimicrobial coatings are often promoted as a way to reduce the spread of infections – on door handles, public transport surfaces, medical devices, and textiles. But one crucial question always comes first: how do we test whether they truly work in realistic everyday use?

In NOVA, this challenge was addressed in Work Package 5 (WP5), which developed and improved testing methods for antimicrobial performance. The work in WP5 tells a clear story: first identifying what is missing in existing standard tests, then developing new methods that better reflect real-life contamination and environmental conditions.

Step 1: Identifying the problem

First, NOVA carried out a gap analysis of existing standardised test methods for antimicrobial materials. Many widely used standards can demonstrate antimicrobial activity in a controlled lab setting, but they often use conditions that are very different from real life – for example unusually large liquid volumes on the surface, very high humidity, long contact times, and simplified contamination scenarios.

Using example use cases such as a hospital touchscreen, medical scrubs, and a train seat cover, the first step showed that to make meaningful claims about performance in use, test methods must better mimic how microbes actually reach surfaces and what conditions they face afterwards.

Step 2: Building better methods for bacteria

Step 2 describes improved approaches to test antibacterial performance under more realistic conditions. Two key developments were:

• a simulated splash test, applying tiny droplets (closer to real contamination events such as coughing or touch transfer) and tracking survival as droplets dry;
• a microchamber method designed for photocatalytic/light-activated coatings, allowing controlled humidity and light/dark comparisons with faster equilibration than large chambers.

This matters because some antimicrobial technologies only work properly under certain humidity or lighting conditions. The second step therefore aimed to connect how a coating works with how it should be tested.

Step 3: Extending the approach to fungi

Step 3 applied similar thinking to antifungal testing. Fungi behave differently from bacteria, and often thrive in moisture-rich environments. WP5 therefore developed:

• a fungal simulated splash test,
• a fungal soak test for harsh “worst-case” conditions (especially relevant to textiles),
• and supporting work on how fungi deposit on surfaces as droplets evaporate.

The goal was again realism: testing under conditions that reflect how fungi might persist and grow in relevant environments.

Step 4: Bringing viruses into realistic surface testing

Viruses can also spread through contaminated surfaces, especially in crowded places. Step 4 therefore developed antiviral testing methods focused on realistic contamination routes:

• an updated simulated splash test using small droplets,
• and the “SneezeBox” concept: a controlled chamber designed to mimic fine particle/aerosol deposition (similar to sneezing or exhaling), followed by surface sampling and measurement.

This work helps bridge the gap between traditional laboratory protocols and the conditions under which antiviral surfaces would actually need to perform.

Step 5: Building a broader evidence base across NOVA coatings and nanoparticles

Alongside method development, WP5 also carried out a larger programme of efficacy testing across the diverse samples provided by NOVA partners – covering both hard surfaces and textiles, and multiple antimicrobial approaches.

A key lesson was that some novel coatings may appear to perform weakly in conventional tests, not because the coating is ineffective, but because the test conditions do not match the coating’s activation mechanism. For example, some standard tests use thick or turbid liquid layers and heavy soiling that can block activating light or neutralise reactive species before they reach microorganisms – especially relevant for light-activated technologies.

In response, WP5 used both modified and newly developed methods that better reflect realistic exposure scenarios by:

• reducing excessive surface liquid and organic soiling (moving towards dry or semi-dry contamination),
• controlling humidity, temperature, and lighting (including dark vs light comparisons),
• and selecting organisms and timepoints suited to the question being asked.

Overall, this body of work supports a more reliable and application-relevant way to judge antimicrobial performance – helping ensure that coatings are assessed fairly, and that claims about their benefits are backed by evidence that reflects real use.

In summary, the work shows how NOVA moved beyond “one-size-fits-all” lab tests. By designing methods that better reflect real contamination events, realistic humidity, drying, and (where relevant) light activation, NOVA strengthened the evidence base for how antimicrobial coatings can be assessed fairly and meaningfully for real applications.