Marangoni-induced actuation of miscible liquid droplets on an incline

• A sustained hydrophilic trace is achieved from treating PDMS surface with PVP.
• Marangoni force allows for uphill propulsion of droplet up to 24° incline.
• Channel width, droplet volume, and contact angle affect propulsion distance.
• Droplet morphology evolves according to key input parameters.
• Good agreement between experimental and numerical values was obtained.

This paper reports on the self-propulsion of a droplet up an incline, confined on a polydimethylsiloxane (PDMS) channel rendered hydrophilic through combined oxygen plasma and polyvinylpyrrolidone (PVP) treatment. Our work investigates the effects of substrate angle on the distance traveled, along with the threshold value for when gravitational force overcomes Marangoni force. A numerical simulation has been developed, where the governing equations solved using COMSOL validated our experimental findings. The numerical simulation, made dimensionless, allows for the prediction of distance traveled and droplet morphology when key parameters in a physical experiment are varied.