Sustained graphene oxide coated superhydrophilicity and superwetting using humidity control

[Display omitted] •Superwetting exhibited when EGFP was applied on roughened PVC coated with GO immediately.•After substrate was stored for 3 h and used, superwetting was lost with the contact angle at 54°.•The average radius spread according to a power-law relationship, and at a faster rate with higher relative humidity.•EGFP deposition was ring-like due to pinning around the islands of GO accumulation.•20 μL water drop in sealed 240-mL container kept relative humidity at 80 % for 150 min. The use of superhydrophilic surfaces for superwetting applications can be hampered by their wetting degradation over time. In this work, superhydrophilic surfaces were fabricated by graphene oxide (GO) deposition on roughened polyvinyl chloride (PVC) substrates. These surfaces were found to exhibit zero contact angle when enhanced green fluorescent protein (EGFP) was deposited on the surface immediately after GO was applied. However, when the GO-coated substrate was stored for 3 h, the surface displayed a contact angle of 54°. The main contact line spreading of the EGFP drop was more easily discernible using normal (500 lx, low glare and shadow free) lighting than with blue LED lighting in the dark. The average radius of the spreading main contact line was found to follow a power-law relationship that increased at a faster rate with higher relative humidity. Confocal imaging revealed rings of EGFP deposition following superwetting that is attributable to pinning around the islands of GO accumulation. Substrate superhydrophilic and superwetting properties can be preserved by adequate control of relative humidity. Relative humidity of 80 % was easily maintained for 150 min by incorporating a 20 μL water drop in a sealed 240-mL container.