Ultrasensitive microresonator based on molecular imprinted hydrogels

• Applicants: Professor Dr.-Ing. Hans-Jörg Bart; Professor Dr. Egbert Oesterschulze
• Subject Area: Chemical and Thermal Process Engineering ; Experimental Condensed Matter Physics
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259794448

The main goal of the project is to implement a conceptual new, low-loss shearing microresonator with an integrated molecular imprinted hydrogel to enable ultrasensitive specific recognition of chemical or biological compounds from liquid phases. The vision of the project is the development of chemical selective microsensors for fast and reliable analytics (e.g. doping tests, clinical analysis). A liquid flow cell environment will provide stable operation and reusability, which has also a positive cost impact.This highly interdisciplinary research activity affords the close collaboration of physicist and chemical engineers merging the scientific fields of 1) low-loss microresonators (quality factor higher than 100) in viscous fluids with high sensitivity and 2) thin films of molecular imprinted hydrogels with their enormous selectivity to a variety of chemical compounds. Chemical selectivity relies on the molecular imprinting process with an analyte during synthesis. The selective uptake of an analyte from a liquid increases the overall mass/inertia of the microresonator. This causes the reduction of the resonant frequency which is accessible with high accuracy implementing the patented concept of partial immersion for microresonators in liquid contact. The improvement of the quality factor during fluid operation and thus the achieved further reduction of the mass detection limit were recently demonstrated in this project introducing a novel adapted shearing bridge microresonator. The important achievements for the integration of the responsive gel layers were the development of a suitable dry etching process as well as the improvement of the adhesion to the underlying microresonator surface. In summary, the key requirements to combine both scientific areas of expertise were successfully implemented in the first project period. In the third research year a chemoselective resonator will be implemented via a molecular imprinting process using the analyte during hydrogel formation. This creates structural specific 3D cavities with appropriate intermolecular properties (hydrogen bounds, etc.), similar to a lock-and-key principle. This needs an adjustment of our developed synthesis protocols and also allows a backwash of the analyte and reuse of the gel (swelling-shrinking via pH or temperature adjustable). We will focus on a well-known model system from previous works, two xanthine derivatives, caffeine and cefazoline (theophylline). With this model system the limits of sensory properties, like selectivity, sensitivity, cross selectivity, and time behavior will be determined. To guarantee reproducibility and maintain partial wetting, the microresonator will be integrated and operated into an optimized fluid cell environment.

• DFG Programme: Research Grants