Oscillatory Microdroplet Constituted Urea Biosensor Stimulated by Acoustic Waves

A proof of concept microdroplet based urea biosensor has been presented that employs a facile but robust detection technique. To substantiate, variation in electrical resistance across a 10 µL salt-laden water microdroplet placed on a glass substrate was observed when it was subjected to sinusoidal acoustic waves at its natural frequency, ~ 320 Hz. For the biosensing application, the conducting water microdroplet was loaded with a suspension of urease-linked gold/cadmium sulfide nanocomposite. Upon adding urea solution in the droplet under the influence of acoustic waves, the changing electrical resistance could be effectively correlated with the changing urea concentration. Higher reaction rate was observed owing to the presence of nanocomposites which provided enzymatic stability and higher interfacial area. Also, the confined droplet geometry resulted in formation of vortices that improved the mixing characteristics. A calibration chart was prepared across a wide range of urea concentrations that was employed for working with unknown human serum samples.
Reference
S. Thakur, M. Bhattacharjee, A. K. Dasmahapatra, D. Bandyopadhyay, Acoustic wave catalyzed urea detection utilizing a pulsatile microdroplet sensor. ACS Sustainable Chem. Eng. 7, 12069 (2019).