This paper presents a novel fabrication methodology for generating superhydrophobic surfaces on stainless steel. The Wire Electric Discharge Machining (WEDM) technique was utilized to change the wettability of stainless steel which is generally hydrophilic. Superhydrophobic surfaces were obtained on the stainless steel by strictly control the machining progress. The mechanism of wettability modulation was explored using the well-established surface metrology and characterisation instruments. It was noted that WEDM can be used to generate a recast layer on stainless steel surface. There was a number of hierarchic micro-structures in the irregular recast layer and the number of micro-holes increases the contact area between the water drop and the top surface of stainless steel. Thus, the contact angle was significantly increased and the wettability of stainless steel changed from hydrophilic into hydrophobic. Compared with other established fabrication approaches, the stainless steel based hydrophobic surface can provide long durability, high efficiency and low cost metallic surfaces, which paves the way for the practical applications of stainless steel hydrophobic surfaces in the academic and engineering fields.
In nature, insects and plants have evolved ways of living and reproducing themselves using the least amount of resource.
This involves both efficiency in metabolism and optimal mechanisms and materials for life functions. Human beings
have long tried to learn from and mimic nature. The study of biological materials has received increasing interest in
recent years due to the often extraordinary mechanical properties and unusual structures exhibited by these materials.
Micro-structure biomaterials exhibit important local variations of elasticity due to the complex and anisotropic
composition. In this paper, a specially developed multi-function tribological probe microscope (TPM) has been used to
map the mechanical properties of some special micro-structured biomaterials. Results of the mapped surface topography
and elastic modulus on specimens of elytra cuticle of dung beetle, nacre of shell and bovine horn have shown some
significant lateral variations of elasticity across the surface area.
Surface mechanical and thermal properties objectively affect our touch-feel perception. However, it is still far from
known that how the surface properties affect the stimulus to our nerve system and make us feel warm or cold, hard or
soft, rough or smooth, etc. Physically, although the surface properties can be measured individually by different
instruments, it is desirable to have a multifunctional instrument to facilitate the investigation of the relationship between
the surface physical characteristics and the corresponding perceived touch feeling by human. In our previous work, a
novel multi-functional tribological probe microscope (TPM) was developed to provide mappings of four functions of a
surface at micro and nanometer scales. The four functions of surface topography, hardness, Young's modulus and
friction are measured in a single scan set-up and they are potentially linked in space and time to provide cross-correlation
in between. In this paper, to achieve the additional function of micro thermal analysis, we proposed a new scheme of
thermal probe with a hot wire (Wollaston wire) buried beneath a Berkovich diamond indenter. The details of mechanical
design and associated electronic circuits are presented. Meanwhile, the paper also explains the principle of the hot-tip
technique by relating its signals to established physical parameters of materials, a method that separates sample
information from the artifact caused by the indentation geometry of the diamond tip. Experimental results of thermal
conductivity measurements on certain metal specimens are discussed.