Among numerous challenges to meet the rising global energy demand in a sustainable manner, improving phase change heat transfer has been at the forefront of engineering research for decades. The high heat transfer rates associated with phase change heat transfer are essential to energy and industry applications; but phase change is also inherently associated with poor thermodynamic efficiencies at low heat flux, and violent instabilities at high heat flux. Engineers have tried since the 1930's to fabricate solid surfaces that improve phase change heat transfer. The development of micro and nanotechnologies has made feasible the high-resolution control of surface texture and chemistry over length scales ranging from molecular levels to centimeters. This paper reviews the fabrication techniques available for metallic and siliconbased surfaces, considering sintered and polymeric coatings. The influence of such surfaces in multiphase processes of high practical interest, e.g. boiling, condensation, freezing, and the associated physical phenomena are reviewed. The case is made that while engineers are in principle able to manufacture surfaces with optimum nucleation or thermofluid transport characteristics, more theoretical and experimental efforts are needed to guide the design and cost-effective fabrication of surfaces that not only satisfy the existing technological needs, but also catalyze new discoveries.

Superhydrophobic surfaces with the self-cleaning behavior of lotus leaves are sought for drag reduction and phase change heat transfer applications. These superrepellent surfaces have traditionally been fabricated by random or deterministic texturing of a hydrophobic material. Recently, superrepellent surfaces have also been made from hydrophilic materials, by deterministic texturing using photolithography, without low-surface energy coating. Here, we show that hydrophilic materials can also be made superrepellent to water by chemical texturing, a stochastic rather than deterministic process. These metallic surfaces are the first analog of lotus leaves, in terms of wettability, texture and repellency. A mechanistic model is also proposed to describe the influence of multiple tiers of roughness on wettability and repellency. This demonstrated ability to make hydrophilic materials superrepellent without deterministic structuring or additional coatings opens the way to large scale and robust manufacturing of superrepellent surfaces.

Exploiting interfacial excess (Γ), Laplace pressure jump (ΔP), surface work, and coupling them to surface reactivity have led to the synthesis of undercooled metal particles. Metastability is maintained by a core-shell particle architecture. Fracture of the thin shell leads to solidification with concomitant sintering. Applying Scherer's constitutive model for loaddriven viscous sintering on the undercooled particles implies that they can form conductive traces. Combining metastability to eliminate heat and robustness of viscous sintering, an array of conductive metallic traces can be prepared, leading to plethora of devices on various flexible and/or heat sensitive substrates. Besides mechanical sintering, chemical sintering can be performed, which negates the need of either heat or load. In the latter, connectivity is hypothesized to occur via a Frenkel's theory of sintering type mechanism. This work reports heat-free, ambient fabrication of metallic conductive interconnects and traces on all types of substrates.