We have generated PFAS-free, smooth surfaces with the lowest ever reported static droplet friction.
The findings are published today in ACS Applied Materials and Interfaces, led by JAE HYUNG CHO, Isaac Gresham and Anthony Katselas from University of Sydney and Glen McHale from The University of Edinburgh. We unveiled a new method to create ultra-low friction surfaces obtained by grafting liquid-like polymer chains to solid surfaces, that could advance many industries.
Link here.
The new method involves spin-coating hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxy poly-ethylene glycol (mPEG), applied through a two-step spin coating process. This method results in slippery layers with both polymers grafted in a mixed layer, so the contact angle values are tunable based on surface fraction of each component, ranging from 38° to 110°. Remarkably, we achieved a contact angle hysteresis of just 0.9 ± 0.3° on the mPEG hydrophilic surface, which represents the lowest contact line friction ever observed on a solid planar surface.
Atomic force microscopy mapping confirmed that the hydrophobic and hydrophilic polymers are fully mixed on the surface, even at high surface fraction of both components. We model our results well with the approach taken by Reyssat and Quéré, in which the majority component is slippery and “perfect” and the sites of the minority component pin the contact line.
These mixed layers serve as excellent model systems for studying interfacial phenomena such as wetting, adhesion, and friction. They also hold promise for practical applications, including enhanced heat transfer, efficient atmospheric water capture, and antifouling technologies.