Life Span of Slippery Lubricant Infused Surfaces

Abstract

Since their discovery a decade ago, slippery liquid infused porous surfaces (SLIPSs) or lubricant infused surfaces (LISs) have been demonstrated time and again to have immense potential for a plethora of applications. Of these, one of the most promising is enhancing the energy efficiency of both thermoelectric and organic Rankine cycle power generation via enhanced vapor condensation. However, utilization of SLIPSs in the energy sector remains limited due to the poor understanding of their life span. Here, we use controlled conditions to conduct multimonth steam and ethanol condensation tests on ultrascalable nanostructured copper oxide structured surfaces impregnated with mineral and fluorinated lubricants having differing viscosities (9.7 mPa·s < μ < 5216 mPa·s) and chemical structures. Our study demonstrates that SLIPSs lose their hydrophobicity during steam condensation after 1 month due to condensate cloaking. However, these same SLIPSs maintain nonwetting after 5 months of ethanol condensation due to the absence of cloaking. Surfaces impregnated with higher viscosity oil (5216 mPa·s) increase the life span to more than 8 months of continuous ethanol condensation. Vapor shear tests revealed that SLIPSs do not undergo oil depletion during exposure to 10 m/s gas flows, critical to condenser implementation where single-phase superheated vapor impingement is prevalent. Furthermore, higher viscosity SLIPSs are shown to maintain good stability after exposure to 200 °C air. A subset of the durable SLIPSs did not show change in slipperiness after submerging in stagnant water and ethanol for up to 2 weeks, critical to condenser implementation where single-phase condensate immersion is prevalent. Our work not only demonstrates design methods and longevity statistics for slippery nanoengineered surfaces undergoing long-term dropwise condensation of steam and ethanol but also develops the fundamental design guidelines for creating durable slippery liquid infused surfaces.

Advances in micro and nanoengineered surfaces for enhancing boiling and condensation heat transfer: a review

“…Micro-pin n fences also demonstrate lower wall temperature uctuation due to the stable annular ow. 171 Building on this work, silicon nanowire pin n fences enable even better performance when compared to micro-pin n fences due to higher capillary pressure. 172 This is seen in the exit vapor quality being 15% higher than that of micro-pin n fence boiling for constant temperature boundary conditions.…”

Ultrascalable Surface Structuring Strategy of Metal Additively Manufactured Materials for Enhanced Condensation

“…Durability of LISs resulting from the depletion of lubricant is a concern, limiting their long‐term application. Even though there has been recent success in prolonging the life span of LISs to beyond 8 months when condensing ethanol, [ 72 ] further improving the longevity of the surfaces is required. In the future, it would be interesting to determine AM LIS performance in retaining the lubricant and identifying how the AM structure morphology can be further optimized to limit lubricant depletion.…”

Manipulation of droplets and bubbles for thermal applications

“…Several other failure mechanisms of LIS such as displacement of the lubricant by the impinging fluid, miscibility of the impinging fluid and the lubricant, and incomplete wetting of the lubricant in the porous substrate for condensation applications are discussed in recent works 64,65 . Furthermore, Hoque et al 71 experimentally investigated the effect of cloaking and lubricants viscosities on the lifespan of LIS and outlined the design guidelines of LIS for different working environments.…”

“…miscibility of the impinging fluid and the lubricant, and incomplete wetting of the lubricant in the porous substrate for condensation applications are discussed in recent works. 64,65 Furthermore, Hoque et al 71 experimentally investigated the effect of cloaking and lubricants viscosities on the lifespan of LIS and outlined the design guidelines of LIS for different working environments. QLS, on the other hand, is shown to address the durability or liquid depletion challenges faced by LIS.…”