Ultrasound-Mediated Chemical Sensing Using Titanium Dioxide (TiO2) Nanoparticles-Embedded Hydrogel with Possibilities of Performance Enhancement Using Machine Learning

In situ chemical sensing, such as temperature, pH, or a specific molecule, is important in healthcare and environmental monitoring [1]. The principle of chemical sensing usually involves multiple elements, including receptor, transducer, and a complex readout circuit. The receptor selectively detects chemical information, which is then translated into electrical signals by the transducer. However, the receptor is usually consumable, and the transducer requires frequent calibration due to the accumulation of chemical species (e.g., protein, biofilm). More recently, hydrogel-based sensing mechanisms based on the incorporation of micro/nanoparticles onto the polymeric network of hydrogels have been reported [2]. For instance, Holtz et al. demonstrated crystalline colloidal particles polymerized within a hydrogel allowed the change of color in response to glucose [3]. Another effort by our group was embedding silica bead in a pH-sensitive hydrogel, which can be interrogated by ultrasound imaging [4].