Absorption Based Characterization Method for Fluid Properties Using Electrowetting-on-Dielectric Forces: Modeling and Fabrication

Electrowetting-on-Dielectrics (EWOD) can be used to build a device, where a polar fluid droplet gets actuated between two EWOD electrodes. In our setup, each electrode is located between a laser diode and an oppositely arranged photo diode. In that manner, the presence of a fluid droplet located above one certain electrode can be optically detected by means of this transmission setup. The droplet’s viscosity dependent switching time, i.e., the time it takes to move the droplet between these two electrodes can be obtained by a time difference measurement of both transmission signals. CFD simulations of the switching time, which depends on the droplet’s viscosity, and furthermore absorption simulations according to the Beer Lambert law have been carried out with DI water as a sample fluid. A low-cost and rapid fabrication method of the so called absorption EWOD (aEWOD) switch is reported and the fabricated EWOD stack is characterized with the aid of surface profilometry

Drug dosage for microneedle-based transdermal drug delivery systems utilizing evaporation-induced droplet transport

We present a setup for directed loading of standard microneedle arrays for transdermal drug delivery with the respective therapeutic agent. The necessity to dose medical drugs according to their particular utilization requires an exact volumetric measure of the particular drug, which is usually provided as a liquid. This is achieved by arranging a metallic plate above the array featuring a set of holes aligned with the microneedles underneath. The plate is coated with a superhydrophobic layer. To initiate the filling, droplets are deposited on said holes, where the volume needs to be above the desired load for an individual needle, but the exact dosage is not required. Evaporation of these sessile droplets, after some time, leads to the falling of the droplets through the microfluidic plate, delivering an exact amount of liquid drug to the needles underneath. The proposed setup is easy to implement and parallelize, assisting in the task of accurate and high throughput coating of microneedle-based transdermal drug delivery devices.(VLID)435213

Natural rubber for sustainable high-power electrical energy generation

Clean, renewable and abundant sources of energy, such as the vast energy of ocean waves, are untapped today, because no technology exists to convert such mechanical motions to electricity economically. Other sources of mechanical energy, such as motions of people and vibrations of buildings and bridges, can potentially power portable electronics and distributed sensors. Here we show that natural rubber can be used to construct generators of high performance and low cost. Natural rubber has higher elastic modulus, fracture energy and dielectric strength than a commonly studied acrylic elastomer. We demonstrate high energy densities (369 mJ g−1) and high power densities (200 mW g−1), and estimate low levelized cost of electricity (5–11 ct kW−1 h−1). Soft generators based on natural rubber enable clean, low-cost, large-scale generation of electricity.Engineering and Applied Science