wettability – LAMPSe | Greco Group Graz

“Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability”

Dallinger, Alexander, Felix Steinwender, Matthias Gritzner, and Francesco Greco
Publication Date: July 10, 2023
https://doi.org/10.1021/acsanm.3c02066

Abstract

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of Φ_RO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for “lab-on-chip” applications.

LAMPSe is participating in the photo competition held at TU Graz called TU Graz SciPix.

The photos show examples of the everyday research at TU Graz.

Alexander Dallinger is participating with a scanning electron microscope image showing LIG and silver flakes forming a “glacier”.

The everlasting silver glacier
The glacier is formed by silver flakes on mountains of laser-induced graphene, arising from a plastic sheet after scribing with an infrared laser. The glacier is forcing its way down the valley and is connecting the conductive mountains together.

Francesco Greco is participating with a photo made by Matthias Gritzner during his bachelor thesis and shows UV ink contained in microfluidic channels made from hydrophilic and hydrophobic LIG.

Liquid Yin&Yang on laser induced graphene
A Yin&Yang symbol is formed by self-guidance and mixing of fluorescent dyes in water on top of a pattern of Laser Induced Graphene with tunable wettability (superhydrophilic/superhydrophobic).

You can participate in the online voting until the 31.05.2021.

Here you can see video of the microfluidics created with LIG. Fluorescent dyes are deposited on the LIG tracks and are guided down to the bottom because of the hydrophilic properties. At the bottom they come in contact with each other and form a Yin&Yang symbol. The liquid is confined by the hydrophobic LIG on the outside.