Abstract
We developed a novel micro-droplet array system, which is based on the distinct three dimensional mesh screen structure and sintering and oxidation induced thermal-fluid performance. Mesh screen was sintered on a copper substrate by bonding the two components. Non-uniform residue stress is generated along weft wires, with larger stress on weft wire top location than elsewhere. Oxidation of the sintered package forms micro pits with few nanograsses on weft wire top location, due to the stress corrosion mechanism. Nanograsses grow elsewhere to show hydrophobic behavior. Thus, surface-energy-gradient weft wires are formed. Cooling the structure in a wet air environment nucleates water droplets on weft wire top location, which is more “hydrophilic” than elsewhere. Droplet size is well controlled by substrate temperature, air humidity and cooling time. Because warp wires do not contact copper substrate and there is a larger conductive thermal resistance between warp wire and weft wire, warp wires contribute less to condensation but function as supporting structure. The surface energy analysis of drops along weft wires explains why droplet array can be generated on the mesh screen piece. Because the commercial material is used, the droplet system is cost effective and can be used for large scale utilization.
Highlights
Droplet array on a ~m2 scale metallic surface? The techniques of droplet pattern formation for microsystems are difficult to be introduced for large scale utilization
Yoo et al noted that periodic water droplets on a piece of metallic surface can be used to absorb electromagnetic wave, which is attractive for military fighter, tank and warship to avoid radar detection[16]
Preparation of test section consists of two steps: sintering a mesh screen piece on a copper substrate, and test section surface modification to create micro/nano structure
Summary
Droplet array on a ~m2 scale metallic surface? The techniques of droplet pattern formation for microsystems are difficult to be introduced for large scale utilization. Because the material (copper and mesh screen) is commercialized and the sintering technique is mature, the device is cheap and suitable for large scale generation of droplet array. The compression stress induced by the weight is important to keep the close contact between mesh screen and copper substrate. This ensures the local area soldering (not a point soldering) of weft wires with the copper substrate, maintaining relatively uniform temperatures between weft wires and copper block. The sintering process under applied external force caused non-uniform stresses along curved weft wires. The stress is expressed as[19] τ
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
