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Cavities fabricated on the microscale have a wide variety of applications, from microwells for cell cultures, microfluidic channels for drug delivery systems to waveguide structures for RF applications. Micro-cavities are particularly useful for sensing applications, such as cavity-based pressure sensors and gap-based capacitive sensors. Cavity structures have been widely demonstrated in MEMS devices using typical semiconductor processing. However, the development of similar structures for flexible applications poses additional challenges. While flexible cavity structures have been fabricated in laboratory environments, challenges arise when these structures are integrated into a larger flexible sensing device or flexible hybrid electronics system. An additive manufacturing approach to cavity formation is presented which utilizes a 3D screen-printing process and in-situ cure. Patterned micro-structures are formed by building up layers of dielectric ink interspersed as needed with printed conductive traces. A proof-of-concept microfluidic channel-based capacitor is fabricated to demonstrate the potential sensing applications for the fabricated microcavities. 

In this paper, we numerically investigate drop impact on a micro-well substrate to understand the phenomena of non-wettability. The simulation is carried out by solving three-dimensional incompressible Navier–Stokes equations using a density projection method and an adaptive grid refinement algorithm. A very sharp interface reconstruction algorithm, known as the moment-of-fluid method, is utilized to identify the multi-materials and multi-phases present in the computation domain. Our simulations predicted that a micro-well with a deep cavity can significantly reduce a solid–liquid contact in the event of drop impact. The results from the drop impact on the micro-well substrate are compared with results from drop impact on a flat substrate. Significant differences are observed between these two cases in terms of wetted area, spreading ratio, and kinetic energy. Our simulation shows that under the same conditions, a drop is more apt to jump from a micro-well substrate than from a flat surface, resulting in smaller wetted area and shorter contact time. Based on the simulation results, we draw a drop jumping region map. The micro-well substrate has a larger region than the flat surface substrate. Finally, we present a comparative analysis between a flat substrate and a substrate constructed with a dense array of micro-wells and, therefore, show that the array of micro-wells outperforms the smooth substrate with regard to non-wettability and drop wicking capability.