SUMMARY:
- Polymer-based sensors have a wide range of applications including the detection of gases
- Automated microdispensing is a useful technique for rapid prototyping of those sensors
Background
Gas sensors play a vital role in safety assurance, disease detection, pollution monitoring, and climate change research. Due to the varying requirements of these fields, numerous sensor technologies with distinct applications have been developed. Among them, optical gas sensors based on polymers stand out for their versatility, compactness, and ability to operate at room temperature. This article highlights the work of Dr. Marc-Antoine Bianki at Polytechnique Montréal, who has successfully utilized inkjet printing to design and test various optical gas sensor prototypes. His research focuses on measuring the concentration of different gases within mixtures using integrated polymer microdroplets. Since individual polymers often lack gas selectivity, arrays of microdroplets composed of different on the same chip—combined with advanced fabrication techniques—are used to develop and assess multiple sensor designs.
Reasons for Using Inkjet Printing
- Inkjet printing is a powerful tool for rapidly producing microstructures, such as high-quality factor resonators.
- It has been successfully applied in fabricating microdisk lasers and biosensors.
- The technique supports a wide variety of printable polymer inks—such as SU-8 (a photosensitive epoxy), polystyrene (PS), and polyhexamethylene biguanide (PHMB)—enabling the development of diverse and application-specific sensing devices.
Fabrication Process
Drop-on-demand inkjet printing on an Autodrop Gantry is employed to deposit polymer droplets in Step 1. In Step 2, a softbake is performed to remove solvent and partially solidify the structures. In Step 3, the droplets are exposed to UV light to initiate crosslinking. Finally, Step 4 involves etching the silicon substrate using SF₆ plasma to form the pillar structure and release the droplet. The finished sensor structure is shown next to it and used in a measuring setup to check different gas and temperature conditions.
The picture shows the fabrication of polymer sensors on an Autodrop Gantry (A). In (B) the Fabrication process of a polymer microdroplet on a pillar. (C) shows the measuring setup used to test different temperatures and gas concentrations.
An example of an optical sensor used in the research of Dr. Bianki
Utility and Outlook
Through continued testing, Dr. Bianki has demonstrated that these advanced resonators-fabricated via inkjet printing-exhibit both temperature insensitivity and high sensitivity to gas concentrations. The ability to multiplex sensors and customize selectivity through various polymers makes this technology highly versatile, with potential applications ranging from mine safety and breath-based cancer biomarker detection to environmental monitoring of methane emissions in agriculture. With the global gas sensor market projected to grow steadily in the coming years, the relevance and impact of this research are expected to increase significantly. Looking ahead, future integration of polymer arrays with PICs could further enhance the compactness, efficiency, and safety of these sensing systems.
References
Read more in these two papers from Dr Bianki
Acknowledgement
Special thanks to Marc-Antoine Bianki and his colleagues at the Yves-Alain Peter Group at the Polytechnique Montréal for their valuable contributions, insights into this piece. You can find more information on their website at https://www.polymtl.ca/pomp/en/