Search

The transmission of pathogens via touchscreens is a concern both in medical environments regarding nosocomial infections and in public spaces. This study presents the development of a self-disinfecting touchscreen system and its implementation into an existing medical device. The disinfection was achieved by irradiating UVC light laterally into the quartz front glass of the touchscreen. The system also included a two-stage safety shutdown feature to protect users from UVC exposure. To detect the presence of the user’s hand, a proximity sensor behind the front glass of the touch screen was installed in combination with touch input registration. A rapid disinfection of staphylococci was achieved without compromising usability and user safety. The prototype demonstrated a bacterial reduction of 99.96% or 3.4 (±0.36) log levels in less than 1 s. The results suggest that the technology has the potential to make a significant contribution to reducing the transmission of infections in healthcare settings and beyond.

The contamination of surfaces by antibiotic-resistant pathogens presents an escalating challenge, especially on touchscreens in public settings such as hospitals, airports, and means of transport. Traditional chemical cleaning agents are often ineffective and leave behind harmful residues. Thus, the application of optical radiation is gaining relevance as a rapid, effective, and environmentally friendly disinfection method. This study examines the contamination of publicly accessible touchscreens and the efficacy of an irradiation approach for the radiation disinfection of microorganisms on quartz surfaces with UVC LEDs. In this setup, the LED radiation is laterally coupled into a quartz plate that serves as cover glass of a simplified touchscreen model. The process allows for the irradiation of microorganisms on the surface, without the user being exposed to hazardous radiation. To assess the efficacy of the disinfection process, a range of bacteria, mostly ESKAPE surrogates, such as Staphylococcus carnosus, Acinetobacter kookii, Escherichia coli, Enterococcus mundtii, and additionally Micrococcus luteus, were spread over a quartz plate with a homebuilt nebulization system. After operating the side-mounted LEDs for 30 s, a reduction in all bacteria except M. luteus by more than three orders of magnitude was observed. In the case of M. luteus, a significant reduction was achieved after 60 s (p < 0.05). This result demonstrates the potential of side-mounted UVC LEDs for rapid disinfection of touchscreens between two users and thus for reducing the spread of pathogens without irradiating humans.

(1) Background: Applications using touch screens are increasingly deployed in medical facilities, as well as in public areas. When touching the display with fingers, potentially pathogenic microorganisms such as methicillin-resistant Staphylococcus aureus (MRSA) can be transmitted. An automated process to decontaminate the device in between users would be highly useful. (2) Methods: Thin glass plates were superficially contaminated with the non-pathogenic Staphylococcus carnosus in a controlled manner. Subsequently, UVA radiation of 400 or 380 nm was laterally coupled into the glass plate, which acted as a light guide. Contact agar plates recorded the change in the staphylococci concentration over time. Additionally, the UVA radiation emitted by the glass plates was measured and the potential risk to humans assessed. (3) Results: Staphylococci concentration decreased as a result of UVA radiation for both wavelengths. At 400 nm, it took about 7.5 h and at 380 nm about 1 h until a reduction of 90% was reached. To meet higher disinfection requirements, disproportionately longer irradiation times were necessary. The potential UVA irradiation of humans in front of the glass pane was about 35 µW/cm2 or less and posed no risk to humans. (4) Conclusions: Side-coupled UVA radiation is in principle capable of safely automatically disinfecting microorganisms on touch screens. However, the required irradiation times are still in the hour range, so that a rapid disinfection within a minute or less is not yet possible with the presented setup. However, higher UVA intensities might reduce the current disinfection durations.

(1) Background: Influenza is a viral infection that has claimed many millions of lives over the past 100 years, and there is always a risk that a new influenza virus will emerge and cause another pandemic. One way to reduce such a potential new influenza virus will be heat inactivation. The question in this study is how much the heat sensitivities of previous influenza viruses differ. If they are very similar, it is expected that a new influenza virus can be inactivated with the same heat parameters as previous influenza viruses. (2) Methods: Through a literature search, published heat inactivation results are compiled and analyzed using Arrhenius models and regression equations for decimal reduction times for different temperatures and media determined. (3) Results: There are about 50 studies on heat inactivation of human and avian influenza viruses so far, showing large differences in heat sensitivity of influenza viruses in different media. However, within a single medium the differences between viruses are rather small. (4) Conclusions: At a temperature of 60 °C, previous influenza viruses can be reduced by 4 or more orders of magnitude within approximately 30 min in almost all media, and this is likely to be true for a potential new influenza virus. Further studies, especially on human influenza viruses, would be desirable.

(1) Background: Hand hygiene with chemical disinfectants is an important measure to reduce the spread of infections, but frequent use can cause skin irritation. In recent years, it has become widely accepted that visible light can also have an antimicrobial effect, and visible light has even been applied to the disinfection of wounds. The present study aims to evaluate whether hand disinfection with visible light is a realistic alternative to chemical disinfectants. (2) Methods: Human hands were irradiated with a dose of 10 or 33 J/cm2 of visible violet light (405 nm) for 3 or 10 min, respectively. The reducing effect of the visible violet light was determined by comparing the contact agar plate results of irradiated and non-irradiated hands. Comparative experiments with a conventional hand disinfecting gel were also performed. Applicable standards were consulted to evaluate skin exposure to the irradiation. (3) Results: Irradiation of the hands with 10 and 33 J/cm2 resulted in an average reduction of microorganisms on the skin of 0.43 and 0.76 log-levels, respectively. These disinfection results with visible violet light are far behind those of the disinfectant gel, which achieved a reduction of 2.17 log-levels. Additionally, due to legal limits, a 3-min irradiation can only be performed five times per day and a 10-min procedure only once. (4) Conclusion: Since the irradiation doses applied up to now have not provided a substantial antimicrobial effect, and since an increase in the dose in a short time period is not arbitrarily possible without heating the hand unpleasantly, visible light of 405 nm seems rather unsuitable for repeated hand disinfection.

(1) Background: Far-UVC radiation in the spectral range 200–230 nm has, according to previous findings, a strong antimicrobial effect on pathogens, but exhibits hardly any harmful effect on human skin. Therefore, the present study will discuss whether such radiation could also be suitable for hand disinfection in the healthcare sector. (2) Methods: Hands and gloves were microbially contaminated and exposed to radiation from a 222 nm krypton-chloride-excimer lamp. The applied doses were 23 mJ/cm2 and 100 mJ/cm2, respectively. Irradiated and non-irradiated hands and gloves were pressed onto agar plates and colonies were counted and compared after 24 h of incubation. For comparison, we also treated hands and gloves with a commercial liquid alcohol-based disinfectant. (3) Results: On the hand, the 23 mJ/cm2 resulted in the reduction of the observed colonies on the agar plates by one log level. For the gloves irradiated with 100 mJ/cm2, a colony reduction of 1.3 log levels was recorded. In the comparative experiments with the commercial disinfectant, a colony reduction of 1.9 and approximately one log level was observed on hand and gloves, respectively. (4) Conclusion: In both cases, far-UVC radiation provided a considerable reduction in microorganisms. However, compared to published far-UVC irradiation results in suspensions, the disinfection success on hands and gloves was rather low. With regard to the irradiation limits currently existing in the European Union, multiple daily hand disinfection with far-UVC radiation is actually legally not possible at present, but the thresholds are currently under discussion and could change in the future. Far-UVC disinfection of hands in gloves seems theoretically possible if attention is paid to potential perforations in the gloves.