DBR PSi/PMMA composite materials for smart patch application

New nanostructured composite materials based on porous silicon (PSi) have been developed as a smart patch type for drug delivery applications. Distributed Bragg reflector (DBR) PSi films and caffeine-impregnated polymethyl methacrylate (PMMA) are used to produce flexible and stable composite materials in which the porous silicon matrix is covered with polymer. DBR PSi films and the composite films display a reflection at 520 and 555 nm in the optical reflectivity spectrum, respectively. These composite materials are stable in aqueous buffer solutions without any degradation for 3 days. The release of caffeine and the shift of reflection peak were simultaneously measured by the use of UV–vis and reflectance spectrometer. The intensity of reflection peak from the composite film is exponentially decreased with a caffeine release. The blue shift of reflection peak results in the decrease of refractive index of composite materials during the caffeine release. The concentration of released caffeine exhibits an exponential relationship with a release time.