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Fabrication of super‐hydrophobic stainless steel needles and evaluation of their drag reduction properties

Naturally, some living things have non-wettable super-hydrophobic surfaces that depend on surface roughness and surface chemistry. Mimicking such super-hydrophobic surfaces has applications for pain reduction and improving the functionality of needles used in health care. This study prepared a stainless steel needle with a super-hydrophobic surface using ultrasonic etching for microstructure fabrication and surface fluorination. The as-prepared stainless steel needle was super-hydrophobic, as evidenced by a water contact angle of 151.3°. Investigations into the effect of ultrasonic etch time on wettability indicated that microstructures on the surface of the stainless steel needle were important for developing super-hydrophobicity. Resistance properties of the as-prepared stainless steel needle were also governed by surface morphology. Super-hydrophobic stainless steel needles have self-cleaning and low adhesion properties and a drag reduction effect that may reduce pain during a puncture process. Simultaneously, the bionic needle with super-hydrophobic property has more applications in biological antibacterial, and reducing retention of expensive reagents. Furthermore, this method can also be applied to micropipette tips, and inkjet or bio-printer heads, which will make breakthroughs in small droplets manipulation, biometric, and inkjet printing equipment.