Dynamic wetting of human blood and plasma on various surfaces.

Surface fouling from coagulated blood is a major challenge in medical industry. However, the wetting physics and dynamics of blood on surfaces are not well understood nor are the quantitative influences due to surface and fluid properties. The present study investigates the effect of surface wetting and dynamics resulting for human blood and plasma, namely hemophobicity, on surfaces with different wettability. To examine effects of fluid properties, the wetting characteristics for liquids with Ohnesorge number similar to that of blood and plasma are also considered. Among the tested surfaces, a superhydrophobic, non-fluorinated, nanocomposite coating based on an inexpensive spray application of a polymer/nanoparticle dispersion provided a very high degree of blood and plasma repellency. This was evidenced by advancing contact angles greater than 153° and roll-off angles less than 18°, for both fluids, and no evidence of a blood trail. However, air exposure during the contact angle measurements led to the formation of a thin gel-like protein skin on the surface (even though an anti-coagulant was added), which distorted the receding droplet curvature. This previously unreported feature did not modify the static contact angle but appears to have caused a significant increase in contact angle hysteresis.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling.

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests.

Superhydrophobic resistance to dynamic freshwater biofouling inception.

Superhydrophobic nanotextured surfaces have gained increased usage in various applications due to their non-wetting and self-cleaning abilities. The aim of this study was to investigate nanotextured surfaces with respect to their resistance to the inception of freshwater biofouling at transitional flow conditions. Several coatings were tested including industry standard polyurethane (PUR), polytetrafluoroethylene (PTFE), capstone mixed polyurethane (PUR + CAP) and nanocomposite infused polyurethane (PUR + NC). Each surface was exposed to freshwater conditions in a lake at 4 m s(-1) for a duration of 45 min. The polyurethane exhibited the greatest fouling elements, in terms of both height and number of elements, with the superhydrophobic nanocomposite based polyurethane (PUR + NC) showing very little to no fouling. A correlation between the surface characteristics and the degree of fouling inception was observed.