Acoustic aeration on a sonochemical surface could have a major impact on sensitivity because of the serious reflection/scattering of sound waves. Recently, we found that the trapped air in the crevices can be reduced by covering the surface with a hydrophilic coating, thus preventing the bubble formation upon ultrasound agitation. Here, we developed an epoxy-based hybrid polymer coating that shows greatly enhanced mechanical adhesion on a high-density polyethylene (HDPE) surface. The strong bonding of C-O-C and the benzene ring as the backbone ensures excellent mechanical strength, and the hydrophilic polar groups of -OH/-NH2 on dopamine display bubble suppression. The existing -OH groups in the cross-linked matrix, which is constructed by adding the monomer PEGMA and cross-linker PEGDA, form a strong chemical bond with the HDPE surface via dehydration, which largely enhanced the adhesion force. The coated HDPE surface maintained a low contact angle of less than 45°, which is the critical angle for avoiding bubbles, after a long period period of abrasion cycling of 160 times under 9.8 kPa pressure. The coated HDPE surface displayed excellent bubble removal performance under ultrasound agitation from room temperature to 60 °C. The strengthened mechanical adhesion of the epoxy-based hydrophilic coating displays extensive applications on a variety of surfaces for acoustic bubble removal.
Keywords: HDPE; acoustic bubbles; hydrophilic coating; mechanical adhesion; sonochemistry.