In this work, a new organic light-emitting device (OLED) structure is proposed that allows light-emission from a metal-free device region, thus reducing the hurdles towards an electrically pumped organic solid state laser (OSL). Our design concept employs a stepwise change from a highly conductive but opaque metal part to a highly transparent but less conductive intrinsic emission layer. Here, the high current densities are localized to an area of a few micrometer in square, which is in the range of the mode volume of the transverse mode of an organic vertical-cavity surface-emitting laser (VCSEL). Besides these experimental results, we present findings from simulations which further support the feasibility of our design concept. Using an equivalent circuit approach, representing the current ow in the device, we calculate the time-dependent length of the emission zone and give estimations for appropriate material parameters.

Temperature-responsive hydrogels are polymer particles whose equilibrium size depends on the temperature of the water they are immersed in. Here we present an equivalent circuit model of a temperature-controlled microvalve based on hydrogel particles. The resulting network model consists of three physical subsystems. The thermal subsystem considers the heat capacities and thermal resistances of the layers of the valve and the coupling to the ambient environment. The polymeric subsystem describes the relaxation of the hydrogel particles to the temperature-dependent equilibrium size. The fluidic subsystem consists of the supply channel and a chamber whose cross section varies according to the size of the hydrogel particles. All subsystems are described and coupled within one single circuit. Thus the transient behavior of the valve can be calculated using a circuit simulator. Simulation results for a setup are presented and compared with experiments.