Multiphase Multicomponent Lattice Boltzmann Method for Modelling Wetting on Liquid Infused Surfaces

Liquid infused surfaces (LIS) are a novel class of surfaces inspired by nature (pitcher plants) that repel any kind of liquid. LIS are constructed by impregnating rough, porous or textured surfaces with wetting lubricants, thereby conferring them advantageous surface properties including self-cleaning, anti-fouling, and enhanced heat transfer. These functional surfaces have the potential to solve a wide range of societal, environmental and industrial challenges. Examples range from household food waste, where more than 20% is due to packaging and residues; to mitigating heat exchanger fouling, estimated to be responsible for 2.5% of worldwide CO2 emissions.

Despite their significant potential, however, to date LIS coatings are not yet viable in practice for the vast majority of applications due to their lack of robustness and durability. At a fundamental level, the presence of the lubricant gives rise to a novel but poorly understood class of wetting phenomena due to the rich interplay between the thin lubricant film dynamics and the macroscopic drop dynamics, such as an effective long-range interaction between droplets and delayed coalescence. It also leads to numerous open challenges unique to LIS, such as performance degradation due to lubricant depletion.

Integral to this EPSRC Fellowship project is an innovative numerical approach based on the Lattice Boltzmann method (LBM) to solve the equations of motion for the fluids. A key advantage of LBM is that key coarse-grained molecular information can be incorporated into the description of interfacial phenomena, while remaining computationally tractable to study the macroscopic flow dynamics relevant for LIS. LBM is also highly flexible to account for changes in the interface shape and topology, complex surface geometry, and it is well-suited for high performance computing. The developed simulation framework will be the first that can fully address the complexity of wetting dynamics on LIS, and the code will be made available open source through OpenLB.

Harnessing the LBM simulations and supported by experimental data from four project partners, I will provide the much-needed step change in our understanding of LIS. The expected outcomes include: (i) design criteria that minimise lubricant depletion, considered the main weakness of LIS; (ii) new insights into droplet and lubricant meniscus dynamics on LIS across a wide range of lubricant availability and wettability conditions; and (iii) quantitative models for droplet interactions on LIS mediated by the lubricant. These key challenges are shared by the majority, if not all, of LIS applications. Addressing them is the only way forward to better engineer the design of LIS.

Finally, the computational tools and fundamental insights developed in the project will be exploited to explore two potentially disruptive technologies based on LIS, which are highly relevant for the energy-water-environment nexus in sustainable development. First, I will investigate application in carbon capture, exploiting how liquids can be immobilised in LIS with a large surface to volume ratio, in collaboration with ExxonMobil. More specifically, liquid amine-based CO2 capture is an important and commercially practised method, but the costly infrastructure and operation prohibit its widespread implementation. Excitingly, LIS may provide a solution to a more economical carbon capture method using liquid amine. Second, motivated by the current gap of 47% in global water supply and demand, as well as environmental pressure to reduce the use of surfactants, I will examine new approaches to clean in collaboration with Procter & Gamble. The key idea is to induce dewetting of unwanted liquid droplets on solid surfaces using a thin film of formulation liquid, thus introducing wettability alteration more locally and using much reduced resources.