Patterning of super-hydrophobic structures on permeable sensor membranes

For a disposable smart food monitoring system, a gas sensor membrane is needed that isolates the sensor surface from (dust) particles water droplets. At the same time, this membrane must have a high permeability, a sufficiently fast response times and should be water repellent to avoid blocking of the sensor membrane by condensed water droplets. A method is studied to pattern super-hydrophobic areas on PDMS which is highly permeable by nature. Square grid patterns were made by excimer laser ablation at 248 nm. The ablation process resulted in structures at three different length scales: around 100 m, 10 m and sub-micrometer. By tuning the amount of shots per location, the water contact angle could be varied between 110–170. The influence of line pitch ranging between 100–200 m and laser spot width ranging between 20–200 m were found to be minimal. An experimental setup to measure the permeability of membranes was built. Permeation experiments showed a 29–38% increase of the permeability after patterning. The reported membranes would be ideal for application as a gas sensor protective membrane, being both highly permeable and water repellant.