Layer-by-Layer coating on human hair

Description
Together with the company Wella, LbL coatings were developed for hair that are used either for coloring or for applying special care products. For this purpose, polyelectrolytes were labeled with various dyes and human and animal hair was dyed in just a few steps. As the polymers are only present on the surface of the hair, special polyelectrolyte combinations were developed that allow the color to be largely removed using a harmless detergent without damaging or bleaching the hair with oxidizing agents.

Partner

• Wella GmbH, Darmstadt, Germany

Patents

• L.Dähne, M. Herrlein, S. Schofield, C. Üzum, N. Schelero „Method for treating hair comprising the succes-sive application onto hair of polymeric layers which can be removed to a large extent or even totally in an easy manner upon request of the user by using a cationic surfactant“ US Patent 11,497,940, 2022
• L. Dähne, M. Herrlein, M. Klickermann, T. Schaefer, S. Schofield, C. Üzüm „Method for treating hair comprising the successive applica tion onto hair of polymeric layers which can be removed to a large extent or even totally in an easy manner upon request of the user by using a composition having a pH less than 7“ US Patent 11,052,035, 2021

Encapsulation of tattoo pigments

Description
Due to their different composition and surface chemistry, coloured tattoo pigments are recognized differently by the immune system and are partially removed, which means that the color of the tattoo changes over time.

To prevent this, the different color pigments were encapsulated with identical LbL layers, which on the one hand leveled the removal due to uniform recognition by the immune system and on the other hand kept the pigments as stable as possible in the skin.

Although the encapsulation succeeded very well, the high negative zeta potential combined with the repulsion of the particles led to rapid segregation processes of the pigment mixtures, so that constant shaking was necessary during the tattooing process.

With the help of the working group of Prof. Bäumler at the Charite, LbL coatings were developed that have significantly less influence on cell proliferation than the original pigments.

Finally, fluorescent secret tattoo pigments were developed that only light up and can be recognized in black light.

Partner

• MT. Derm GmbH, Berlin, Germany
• Charité – Universitätsmedizin Berlin, Berlin, Germany

Reference

• P. Laux, T. Tralau, J. Tentschert, A. Blume, W. Bäumler, L. Dähne, J. Serup, et al, A. Luch „A medical-toxicological view of tattoing” Lancet. (2016) 387: 395-402.

Hair coloring with photonic crystals

Description
Photonic crystals are periodic arrangements of objects in the size of light wavelengths. These are able to selectively reflect certain colors, which is used by beetles or birds to color their wings or feathers.

The colorful feathers of the drake, for example, have no dye, but only shimmer due to these structurally formed reflections.

We have produced monodisperse nanoparticles that can be arranged on smooth surfaces in periodic lattices and reflect different colors depending on the particle size. However, the plan to create iridescent hair colors with this technique failed due to the hair structure.

Partner

• Procter & Gamble, Cincinnati, OH, USA

UVA/UVB Sun Protecting capsules

Description
Freshly applied sunscreen absorbs UV-B and UV-A radiation and converts it mainly into heat.

As the small light absorber molecules diffuse into the skin over time, they generate not only heat but also radicals, which damage the skin and cause it to age prematurely.

The light absorbers should therefore be enclosed in microcapsules that adhere firmly to the skin but do not diffuse into it due to their size.

The simultaneous encapsulation of the 3 differently absorbing oily components was achieved in 3 µm porous hydrophobic particles, which were sealed by LbL coating, hydrophilized and provided with a surface that adheres to the skin.

Partner

• Lancaster, MonacoTech, Monaco