Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2014-07-24, 14:56:51 | version 1.32.01
Conventionally, such structures have been fa- bricated using optical lithography or imprint techniques. We developed alternative patterning methods based on particle monolayers with self-as- sembled, regular structures. Polymer spheres were emulsion-polymerized, deposited by convecti- ve assembly, and transferred into the underlying substrate by etching and deposition. In a project in the DFG’s SPP1420 (collaboration with Program Division Functional Surfaces) we used the resulting surfaces to mold polymer fibers as Gecko-like ad- hesives (figure). Applications in optics and sensing are currently under investigation. Ligands and surfactants in particle assembly Surfactants and ligands are molecules that popu- late the surfaces of nanoparticles and emulsion droplets. They stabilize the dispersions and allo- wed us to tune their properties. Less well-studied is their role in the agglomeration and assembly of particles in functional materials. Results obtained in our group indicate that this role often governs agglomerate structure. For example, particles can be assembled into “supraparticles” with defined structures inside emulsion droplets. Experiments performed in 2013 prove that whether the resulting structures are regular or disordered depends on the surfactants stabilizing the emulsion. In so-called “Pickering emulsions”, nanoparticles adsorb at liquid-liquid interfaces and stabilize emulsions. High-quality supraparticles require the exact op- posite: emulsions in which no particles migrate to liquid-liquid interfaces but remain caught inside the droplets. Nanocomposites for electronics and photovoltaics Combinations of inorganic nanoparticles and orga- nic molecules are candidates for robust electronic materials that can be used in printed electronics and large-area, low-cost photovoltaics. A critical prerequisite is the defined distribution of par- ticles and defined interfaces between the particles inside active layers. A recent grant in the “Nano- MatFutur” program of BMBF will let us apply the techniques and insights of the last years to create new particle-based electronic materials. Outlook The Junior Research Group Structure Formation has grown into a well-established unit that links basic research in colloidal and surface chemistry and chemical engineering to material synthesis. New projects connect us to other activities at INM: In the project “AggloTox”, we collaborate with the Program Division Nano Cell Interactions to under- stand and design agglomeration in physiological environments. A project with the Program Divisi- on Biomineralization and LMU Munich seeks artifi- cial models of biomineralized, amorphous precur- sor films. A BMBF project in collaboration with the Program Division Optical Materials and Siemens continues successfully. 17Jahresbericht 2013 / Annual report 2013 A dense array of sub-micron holes in silicon fabricated by particle-based surface micromachining. Such hole arrays are used in a collaboration with Functional Surfaces to create bioinspired adhesives in a project in the DFG’s SPP1420 (inset, lower right).