Replacing the solid needle by a liquid one when measuring static contact angles
Comparison of the traditional solid needle dosing system and a novel pressure-based dosing system, a so-called Liquid Needle
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)  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.