Self-assembled archaea bio-coatings in thermal-fluids systems: A study on adhesion optimization and energy efficiency

Abstract

In this study, adhesion optimization was performed for archaea bio-coatings to be used in thermal-fluids systems. For this, Sulfolobus Solfataricus P2 archaea was coated onto silicon wafer substrate surfaces by polyelectrolyte adhesive layers made of Poly-l-Lysine and Poly-l-Arginine. Polyelectrolyte adsorption is a self-assembling phenomenon where the oppositely charged layers are electrostatically attracted to each other. We herein report the coating performance of samples prepared with two different coating methodologies: Layer-by-Layer and mixed coating. Samples were optimized with respect to thickness and durability by varying the polyelectrolyte concentration, salt concentration, and mixture ratios. A closed loop system was prepared to test the durability of the coated samples against fluid flow, and Atomic Force Microscopy and Surface Profilometer techniques were utilized to characterize the topology and thickness of the samples before and after each test. The results reveal the existence of an optimal configuration for the mixed coated samples, where adding excess charged groups shifted the force balance to either the negative or positive side, decreasing adhesion in both cases. Increasing the ionic strength of the solution resulted in 17% and 20% increases in coating thickness for PLL and PLA samples, respectively. However, in some cases, samples appeared to have worsened durability. After the durability tests, the samples were used to evaluate the heat transfer performance of the coatings in a real thermal-fluids system. The obtained results show enhancements more than 20% in boiling heat transfer.