Available Technology
Fluids identification by chemically patterned inverse opal photonic crystals
Technology:
Patterning chemical functionality in Inverse Opals
Markets Addressed
3D photonic crystals are of great interest for both fundamental and applied research (e.g. optical computers), but chemically patterned 3D photonic crystals are difficult or impossible to achieve via existing techniques. This invention, by selectively modifying defect-free inverse opal 3D crystal structures with organic molecules, enables the fabrication of chemically functionalized 3D photonic crystal patterns. The high uniformity of the structure and the highly controllable spatial diversity of surface chemistry allows different liquids to wet the material in a highly specific way, and can lead to a variety of applications:
1. “pH paper”-like colorimetric indicator for organic liquids: a patterned photonic structure strip, able to distinguish between organic liquids with different wetting properties (e.g. various alcohols), can be used to identify different solvents or solvent mixtures. This is very effective in identifying small spills or unlabelled/abandoned containers that are frequently found in communal lab environments. The “pH paper”-like optical litmus test can also be used to measure alcohol content (or presence of methanol) of alcoholic drinks or to distinguish between grades of petrol.
2. Encryption of optical images: encode secret messages in the photonic structures through local surface functionalization. Depending on the number of different functional groups used, different solvent could reveal different messages, with only intended recipient knowing the correct solvent in which to read the message. Upon solvent evaporation, the encoded message disappears and the local structure returns to its original appearance. The envisioned application of the technique includes a multilevel document, art authentication and message encryption. For an example of multilevel encryption, click here.
3. Invisible microfluidic channels: liquids are allowed to confine in and propagate along the chemically modified channels through capillary processes. As the channels are defined with surface functional groups, they can be easily erased and rewritten in different configurations.
4. Microfluidic channels with fixed configurations and reconfigurable functionality: permanent channels can form by selectively infiltrating material precursors into regions of compatible functionality. These mixing channels can be used as intra-microfluidic chromatography columns for chemical separations, sensors and catalysis.
Innovations and Advantages
Professors Joanna Aizenberg and Marko Lončar’s labs have created a unique method to chemically pattern inverse opal silica structures. It starts with the co-assembly of monodisperse colloidal suspension of PMMA nanospheres with silica sol-gel solution onto a substrate, followed by the removal of colloidal particles with heat (for a description of this invention, click here). Next, the SiO2 walls are functionalized with desired molecular groups via silanization. A physical mask covers selected portions of the 3D structure, outside of which the monolayer is etched away and perhaps replaced with other functional groups. This step can be repeated n times and produce (n+1) different 3D chemical patterns in the same photonic crystal.
The disclosed technique has exhibited very high selectivity in differentiating liquids with very subtle differences in wetting properties through an easily visible color contrast (see the figures). This technique has proven highly effective in mutually distinguishing many solvents like methanol/ethanol/isopropanol (A), different concentrations of ethanol in water (B), simple alkanes (C, hexane, heptane, octane, nonane, decane), or different grades of petroleum (D, gasoline/diesel), etc. Furthermore, the chemically patterned 3D structures serve well as the channels in a chip-scale fluidic platform, inherently containing a highly regular porous matrix, in which the functionalized SiO2 surface can guide different liquids in different directions. Notably, all the chemically patterned photonic crystals can be recycled and re-wrote through acid-piranha cleaning or flood exposure to oxygen plasma for long time, completely removing organic functionalities.
Additional Information
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Inventor(s):
Aizenberg, Joanna
Burgess, Ian Bruce
Hatton, Benjamin D.
Loncar, Marko
Mishchenko, Lidiya
Categories:
- Diagnostic/Biomarkers
- Fluidics/Microfluidics
- Materials
- Photonics, Optics and Optoelectronics
- Sensors and Imaging Devices
For further information, please contact:
Laura Brass, Director of Business Development
(617) 495-3067
Reference Harvard Case #3928