Low‐Friction, Superhydrophobic, and Shape‐Memory Vulcanized Rubber Microspiked Structures

Abstract

Friction is a basically ubiquitous phenomenon, but also an important subject for the development of a sustainable society in terms of energy loss, damage to parts from wear, and so on. [1] Generally, lubricants are used to reduce friction force; however, lubricants are known to pollute the environment. [2] Furthermore, sometimes lubricants have limited applications in that they cannot be used inside the body. In recent years, friction reduction by the use of surface microstructures has attracted a good deal of attention due to the wide range of possible applications. [3] The surfaces of animals, in particular, have been a major focus as they are thought to have developed superior functionality via the evolutionary process of adaptation to their surrounding environments. [4] For example, a snake's body surface has submicron dimpled structures that reduce friction forces. [5] A firebrat, a kind of silverfish, is covered with dense scales with microscale groove structures that also reduce friction forces. [6] A grasshopper stabilizes friction forces in both dry and wet conditions by hexagonally arranged microscale pad structures formed on their leg tips. [7] Moreover, animal surfaces show multifunctionality, such as antireflective and superhydrophobic functions of a moth eye, [8] water repellent and beautiful bluecolored wings of morpho butterfly, [9] and so on. [10] Thus, the induction of surface nano-and microstructures offers great possibilities in not only reducing friction forces, but also in affording additional functions related to the surface nano-and microstructures. The research field associated with the fabrication of such materials, inspired by or mimicking biological surfaces, is known as "biomimetics," and it has already produced a number of important findings; [11] however, biomimetic products are still not in common use due to the major problem of the fragility of the nano-and microstructures. We, therefore, have focused on vulcanized rubber. [12] Vulcanized rubber is commonly used in wide variety of products, such as tires, gaskets, rubber bands, seismic isolation rubber, and so on, due to its durability and elasticity. Vulcanized rubber also

Evaluation of Structure, Heterogeneities, Thickness and Corrosion Protection of Electrodeposited Sol-Gel Superhydrophobic Coatings

“…Nevertheless, further studies are necessary to prove such theory. Elemental mapping on film surface before and after immersion proved the chemical stability of the deposit in NaCl 3.5% wt., and the evaluation of the effect of the amount of precursor in solution indicated high water contact angles (159 o ) and impedance modulus (2x10 7 Ohm.cm 2 ) for the highest amount of precursors herein tested (55 mmol). The film thickness, on the other hand, showed not to grow indefinitely and decreased to 58 µm due to miscibility issues under 55 mmol of precursor.…”

Friction Reduction Effect Caused by Microcontact and Load Dispersion on the Moth‐Eye Structure

“…Furthermore, these reports also show different loading conditions than our experiments, where the friction coefficient of flat surface is constant. Other microstructural friction studies carried out under highload conditions exist, but the principles of friction and contact are different for elastic deformation materials, [4,[36][37][38][39][40] where the coefficient of friction decreases exponentially with increasing load even on unstructured surfaces due to the flexibility of the material. [4][5][6] Although studies of the surface microstructure of plastic deformation materials have been conducted, [12][13][14][15] the reason for the decrease in contact area has remained unclear.…”

Flux Crystal Growth, Crystal Structure, and Magnetic Properties of a Ternary Chromium Disulfide Ba9Cr4S19 with Unusual Cr4S15 Tetramer Units

“…Structure determination of the single crystals was performed by a Rigaku XtaLab mini II diffractometer (Mo Kα radiation). The structure was solved by a dual-space algorithm method ( SHELXT ) 32 and refined by a full-matrix least-squares method with SHELXL , 33 using an Olex 2 graphical user interface. 34 X-ray photoemission spectroscopy (XPS) measurements were performed using a Mg Kα X-ray source (JEOL, JPS-9010MC).…”