Replacing the solid needle by a liquid one when measuring static contact angles



Needle-deposition of sessile drops is a well-established method in contact angle analysis. However, customers regularly
report user-dependent variations of contact angles as well as problems to deposit liquid drops on super-hydrophobic
surfaces, or they demand higher deposition speeds. Here we present a new technique for drop deposition that is based
on a Liquid Needle in contrast to a solid one. Further, we highlight the main findings of a scientific study published in the
Journal of Colloid and Polymer Science (DOI 10.1007/s00396-015-3823-1) [1] where we thoroughly compared both
techniques using 14 different sample surfaces. We show that the resulting contact angles of droplets dosed by either
technique are identical. In addition, we explain how potential pitfalls of needle-dosing – when not carried out very
carefully – are eliminated by the alternative Liquid Needle dosing technique.