Fabrication of elastic, conductive, wear-resistant superhydrophobic composite material

Abstract

A polydimethylsiloxane (PDMS)/Cu superhydrophobic composite material is fabricated by wet etching, electroless plating, and polymer casting. The surface topography of the material emerges from hierarchical micro/nanoscale structures of etched aluminum, which are rigorously copied by plated copper. The resulting material is superhydrophobic (contact angle > 170°, sliding angle < 7° with 7 µL droplets), electrically conductive, elastic and wear resistant. The mechanical durability of both the superhydrophobicity and the metallic conductivity are the key advantages of this material. The material is robust against mechanical abrasion (1000 cycles): the contact angles were only marginally lowered, the sliding angles remained below 10°, and the material retained its superhydrophobicity. The resistivity varied from 0.7 × 10–5 Ωm (virgin) to 5 × 10–5 Ωm (1000 abrasion cycles) and 30 × 10–5 Ωm (3000 abrasion cycles). The material also underwent 10,000 cycles of stretching and bending, which led to only minor changes in superhydrophobicity and the resistivity remained below 90 × 10–5 Ωm.

Study on Preparation of Superhydrophobic Copper Surface by Milling and Its Protective Performance

“…The durability and stability of superhydrophobic surfaces are always important indices to measure the mechanical properties of superhydrophobic surfaces, which greatly affect the practical application of superhydrophobic surfaces. Scratch resistance and friction resistance are usually used to judge the mechanical durability and stability of superhydrophobic surfaces [ 34 , 35 ]. To study the mechanical properties of superhydrophobic Cu samples, a knife scraping test and friction test were selected for MS-30 superhydrophobic Cu samples.…”

Robust and durable liquid-repellent surfaces

“…Based on the similar strategy, they reported a robust PDMS/Cu superhydrophobic composite material that could withstand 1000 cycles of mechanical abrasion and 10 000 cycles of stretching and bending recently. 294 As shown in Fig. 49b, when a hydrophobic TiO 2 nanoparticles coated elastic VHB 4910 film was equi-biaxially stretched with stretch ratio l = 3, the micro/nanostructured TiO 2 clusters were diluted and the film thereby lost its superhydrophobicity, which could be easily recovered by releasing the film (l = 1) due to its excellent elasticity.…”

“…14,43,44,[283][284][285] In recent years, much attention has been paid to the development of liquid-repellent surfaces that can last their liquid repellence for a long time without obvious deterioration under various thermodynamic, mechanical, or chemical stimuli. Meanwhile, some related terminologies, such as thermodynamic/mechanical/chemical stability/robustness/durability, 43,44,[286][287][288][289][290][291] wear/abrasion-resistance, 286,[292][293][294][295] chemical/corrosion resistance, 72,291,296 etc., have been employed to describe the ability of liquid-repellent surfaces to survive in various conditions. Among them, ''stability'' alone sometimes implies that the surfaces are not liable to undergo the damage of liquid repellence on short-term scale, and ''wear-resistance'' only covers the stability of liquid-repellent surfaces towards mechanical wear partially.…”

“…Therefore, endowing the liquid-repellent coating and/or the underneath substrate with elasticity becomes a general method to improve their mechanical durability. 58,153,196,294,375,490 It was demonstrated that compared with rigid superhydrophobic surface, a water droplet impacting an elastic superhydrophobic surface showed a two-fold reduction in the contact time between the droplet and surface. 491 This was attributed to the distinct postimpacting kinetic-to-elastic energy conversion between the droplet and elastic substrate, which enabled the substrate to oscillate upon impacting, and then applied vertical momentum back to the droplet with a springboard effect during the droplet retraction, resulting in a rapid droplet bouncing with reduced contact time and an improved durability towards droplet impacting.…”

“…14,43,44,283–285 In recent years, much attention has been paid to the development of liquid-repellent surfaces that can last their liquid repellence for a long time without obvious deterioration under various thermodynamic, mechanical, or chemical stimuli. Meanwhile, some related terminologies, such as thermodynamic/mechanical/chemical stability/robustness/durability, 43,44,286–291 wear/abrasion-resistance, 286,292–295 chemical/corrosion resistance, 72,291,296 etc. , have been employed to describe the ability of liquid-repellent surfaces to survive in various conditions.…”