Dressings effectively protect the site of an injury, but to examine a wound they must be removed. This can not only be painful for a patient, but it can also allow germs to enter the wound and cause infection.
Now, scientists at the Fraunhofer Research Institution for Modular Solid State Technologies EMFT in Munich have developed dressing materials and plasters, which indicate pathological changes in the skin. If an infection is present, the colour of the dressing changes from yellow to purple.
"We have developed an indicator dye which reacts to different pH values, and we have integrated it into a dressing and a plaster. Healthy skin and healed wounds usually show a pH value of below 5. If this value increases, it is shifting from the acid to the alkaline range, which indicates complications in the healing of the wound. If the pH value is between 6.5 und 8.5 an infection is frequently present and the indicator colour strip turns purple," states Dr. Sabine Trupp, scientist at the EMFT, explaining the chemical reaction.
In this way the intelligent dressing material makes it possible to regularly check wounds from the outside without disrupting the healing process.
Production of the colour control strip posed a number of challenges for the research scientists as it had to meet several different requirements.
"The dye has to remain chemically stable when bonded to the fibres of the dressing material or the plaster to ensure that it does not get into the wound. At the same time, the indicator must show a clear change in colour and also react sensitively in the right pH range," says Trupp.
The experts succeeded in meeting all these requirements. A prototype of the dressing has already been produced and initial tests have proved successful.