Stimuli-responsive photonic materials
Battery-free, cheap optical sensors based on polymer cholesteric liquid crystals can be processed using high speed printing techniques. In such a way, sensors can be produced that are able to, for example, monitor the entire history of exposure of a sample (time-analyte integrators) to a wide variety of stimuli such as temperature, humidity, acetone, oxygen, and carbon dioxide. These sensors are evaluated for applications in food, personal care, medical applications and high-end consumer products. Furthermore, such systems can also be used as stimulus-responsive paints and reflectors which are investing for the architectural and building sectors.
Soft actuators and responsive surfaces
Accurately controlled surface topologies of (sub) micron dimensions provide for a diversity of functionalities. Examples of optical functions are controlled scattering, focusing or defocusing lenses and diffraction. Additionally, mechanical functions, such as friction and adhesion control, hydro- and aerodynamic functions like flow resistivity and mixing, and wetting/dewetting behavior (also known as lotus leaf effect) can be integrated in our designs. It is our objective to make these function adjustable, meaning that a surface topology can be switched between an ‘on’ and an ‘off’ state.
Polymer-based soft actuators are interesting polymer films for a wide variety of low-cost applications, ranging from micromechanical systems such as valves, to propulsion materials inspired by cilia and smart surfaces. Polymeric liquid crystalline materials can undergo mechanical deformation by an external stimulus. Complex reversible deformations can be achieved by imposing a three-dimensional director microstructure on the film, with variation through the thickness of the film as well as across its width.
Smart textiles are a new generation of materials which are applied in many fields, including fashion, medicine, sports, or entertainment. Our work aims at optimization of light distribution from LEDs as well as at developing new concepts for smart coated (thermo- and photoresponsive) textiles. Diffractive and reflective optical coatings are also incorporated into fibers to change their perception and to generate new degrees of freedom for textile and fashion designers. In addition, responsive fibers are developed which react to stimuli such as light, humidity and temperature to produce fabrics which react to environmental conditions. These functional melt-spun and electro-spun fibers are developed in a close collaboration with Queen Mary, Nanoforce, University of London, UK.