Functional Acrylic Surfaces Obtained by Scratching

By using sandpaper of different grit, we have scratched up smooth sheets of acrylic to cover their surfaces with disordered but near parallel micro-grooves. This procedure allowed us to transform the acrylic surface into a functional surface; measuring the capillary rise of silicone oil up to an average height <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mover><mi>h</mi><mo>¯</mo></mover></semantics></math></inline-formula>, we found that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mover><mi>h</mi><mo>¯</mo></mover></semantics></math></inline-formula> evolves as a power law of the form <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mover><mi>h</mi><mo>¯</mo></mover><mo>∼</mo><msup><mi>t</mi><mi>n</mi></msup></mrow></semantics></math></inline-formula>, where <i>t</i> is the elapsed time from the start of the flow and <i>n</i> takes the values 0.40 or 0.50, depending on the different inclinations of the sheets. Such behavior can be understood alluding to the theoretical predictions for the capillary rise in very tight, open capillary wedges. We also explore other functionalities of such surfaces, as the loss of mass of water sessile droplets on them and the generic role of worn surfaces, in the short survival time of SARS-CoV-2, the virus that causes COVID-19.