Encoding complex wettability patterns in chemically functionalized 3D photonic crystals
Written by: Grant England AP225 Fall, 2011
Title: Encoding complex wettability patterns in chemically functionalized 3D photonic crystals
Authors: Ian B. Burgess, Lidiya Mishchenko, Benjamin D. Hatton, Mathias Kolle, Marko Lončar, and Joanna Aizenberg
By creating an inverse-opal film of large area and very high quality, and functionalizing the interior surfaces of these inverse opal films with different types of silanes to change the wettability of the surfaces, colorimetric patterns can be created for differentiation of two liquids by surface tension. This is possible because the color of an inverse opal film with pores filled with air is different from that of an inverse opal film with pores filled with liquid due to the refractive index difference between air and the liquid.
The above figure shows images of the W-INK structures after wiping with different liquids with varying surface tensions.
Methods and Results
The above figure shows the patterning process using two different silanes with different wettability properties. By taking advantage of the finite speed of infiltration of the silane into the pores, and using a mask to block off areas not to be coated in the silane, areas coated with several different silanes (and therefore having differing wettability properties) can be created on the same inverse opal film. Thus, once sample can be created which can differentiate between several different surface tensions (and therefore, several different liquids).
By patterning different kinds of silanes onto the same film, devices akin to litmus paper can be created to differentiate similar liquids by a method other than pH can be created. The ease of use of such devices, along with their limited reusability could enable the creation of a new class of tools for chemistry labs to easily verify the surface tension (within a range) of liquids.