Medical devices such as surgical suture needles are commonly coated with various silicone formulations, such as polydimethylsiloxane, to enhance the penetration performance through tissue. However, the silicones that improve lubricity also wear off the needle surface during suturing and, therefore, the force required to penetrate tissue increases with successive passes. Consequently, conventionally coated suture needles are unable to maintain lubricity as they may be passed through tissue up to 50 times, depending on the surgical procedure. The result is an increase in penetration force with successive passes, which, minimally, is a frustration to surgeons. Lubricity may be sacrificed at the expense of making a more durable coating with excellent adhesion. Likewise, many lubricious coating materials exist that do not adhere well to the relevant substrate. The key is to produce a coating that is lubricious, yet durable enough to withstand multiple contacts with tissue.

The coating system described in this paper is comprised of polydimethylsiloxane dissolved in various solvents with polyolefin waxes added to form a suspension. The coating is applied to surgical needles via a dip coating process. During curing of the coating, a two-phase structure forms that retains the lubricity of silicone over multiple passes. Testing of penetration force in both synthetic (Porvair) and natural (excised human skin) media was performed to quantify the coating properties and compare to conventional silicone coatings. These test results as well as the coating morphology and theories on the mechanism of adhesion will be discussed in this paper.