Biofilms can be found everywhere and can form on almost any surface, as long as there is enough moisture. The word biofilm describes an accumulation of microorganisms, mostly bacteria, which live in close community within a mucous substance. Since biofilms are very persistent, they represent a hitherto unsolved problem in many areas of daily life.
Especially in medicine there is a high risk of infection due to the growth of biofilms on implants and catheters. In fact, pathogens in over 60% of infectious diseases cannot be effectively treated because they are protected by the biofilm.
The biofilm has many advantages for the bacteria: they are protected against antimicrobial substances such as antibiotics and disinfectants and are much more resistant to mechanical influences. Typical examples are fingerprint sensors whose surface is touched continuously and thousand fold by fingers. On the touch surface, biofilm growth is supported by perspiration and other microbial secretions. The risk of germ transmission from user to user is extremely high. To date, there is no method with which biofilms can be effectively prevented or specifically inactivated.
Within the framework of an internal funding project called “BiClean” and taking fingerprint sensors as an application example, the researchers coated bidirectional displays with titanium dioxide (TiO2) or TiO2-containing layer combinations that can inactivate a biofilm upon light exposure. Bidirectional displays can emit light or content as well as detect and evaluate the incoming light via an integrated camera function. This allows the display to record the surface status and makes it possible to detect the formation of biofilms and then start a cleaning interval depending on the degree of contamination.