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 degrees. 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.