title: Self-spinning nanoparticle laden microdroplets for sensing and energy harvesting.
abstract: Exposure of a volatile organic vapour could set in powerful rotational motion a microdroplet composed of an aqueous salt solution loaded with metal nanoparticles. The solutal Marangoni motion on the surface originating from the sharp difference in the surface tension of water and organic vapour stimulated the strong vortices inside the droplet. The vapour sources of methanol, ethanol, diethyl ether, toluene, and chloroform stimulated motions of different magnitudes could easily be correlated to the surface tension gradient on the drop surface. Interestingly, when the nanoparticle laden droplet of aqueous salt solution was connected to an external electric circuit through a pair of electrodes, an ∼85-95% reduction in the electrical resistance was observed across the spinning droplet. The extent of reduction in the resistance was found to have a correlation with the difference in the surface tension of the vapour source and the water droplet, which could be employed to distinguish the vapour sources. Remarkably, the power density of the same prototype was estimated to be around 7 μW cm(-2), which indicated the potential of the phenomenon in converting surface energy into electrical in a non-destructive manner and under ambient conditions. Theoretical analysis uncovered that the difference in the ζ-potential near the electrodes was the major reason for the voltage generation. The prototype could also detect the repeated exposure and withdrawal of vapour sources, which helped in the development of a proof-of-concept detector to sense alcohol issuing out of the human breathing system.
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, India. dipban@iitg.ernet.in.
authors.forename: Mitradip
authors.initials: M
authors.lastname: Bhattacharjee
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, India.
authors.forename: Viswanath
authors.initials: V
authors.lastname: Pasumarthi
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Guwahati, India.
authors.forename: Joydip
authors.initials: J
authors.lastname: Chaudhuri
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, India. dipban@iitg.ernet.in.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Singh
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, India. dipban@iitg.ernet.in and Department of Electronics and Electrical Engineering, Indian Institute of Technology Guwahati, India.
authors.forename: Harshal
authors.initials: H
authors.lastname: Nemade
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, India. dipban@iitg.ernet.in and Department of Chemical Engineering, Indian Institute of Technology Guwahati, India.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Bandyopadhyay
mesh_terms: D000327:Adsorption; D000428:Alcohol Drinking; D001944:Breath Tests / Q000379:methods*; D002725:Chloroform / Q000737:chemistry; D004566:Electrodes; D000431:Ethanol / Q000737:chemistry; D004986:Ether / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D015233:Models, Statistical; D009038:Motion; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods; D012834:Silver / Q000737:chemistry; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents; D014050:Toluene / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D013501:Surface-Active Agents; D014867:Water; D004986:Ether; D014050:Toluene; D000431:Ethanol; D012834:Silver; D006046:Gold; D002725:Chloroform; D000432:Methanol