Applying Droplets and Films in Evaporative Lithography

Abstract

The review covers experimental results of evaporative lithography and analyzes existing mathematical models of this method. Evaporating droplets and films are applied in different fields, such as cooling of heated surfaces of electronic devices, diagnostics in health care, creation of transparent conductive coatings on flexible substrates, surface patterning. A method called evaporative lithography emerged after establishing the connection between the coffee ring effect taking place in drying colloidal droplets, and naturally occuring inhomogeneous vapor flow densities from fluid-vapor interfaces. Essential control of the colloidal particle deposit patterns is achieved in this method by producing ambient conditions that induce a nonuniform evaporation profile from the colloidal liquid surface. Evaporative lithography is part of a wider field, which is known as "Evaporative-induced self-assembly" (EISA). EISA involves methods based on the contact line processes, methods employing particle interaction effects and evaporative lithography. As a rule, evaporative lithography is a flexible and single-stage process with such advantages as simplicity, low price and possibility of application to almost any substrate without pretreatment. Since no mechanical impact on a template is present in evaporative lithography, the template integrity is preserved in the process. The method is also useful for creating materials with localized functions, such as slipperiness and self-healing. For these reasons, evaporative lithography attracts increasing attention and has a number of noticeable achievements at present. We also analyze limitations of the approach and ways of its further development.