A unique, versatile, and material-independent approach to contactlessly merge two chemically distinct droplets suspended in an acoustic levitator is reported. Large-amplitude axial oscillations are induced in the top droplet by the low-frequency amplitude modulation of the 58 kHz ultrasonic carrier wave, which causes the top sample to merge with the sample in the pressure node below. The levitator is enclosed within a pressure-compatible process chamber to control the environmental conditions. The merging technique permits precise control of the substances affecting the chemical reactions, the sample temperature, the volumes of the liquid reactants down to the picolitre range, and the mixing locations in space and time. The performance of this approach is demonstrated by merging droplets of water (H2O) and ethanol (C2H5OH), conducting an acid-base reaction between aqueous droplets of sodium hydroxycarbonate (NaHCO3) and acetic acid (CH3COOH), by oxidizing a droplet of hypergolic ionic liquid with nitric acid (HNO3), and the coalescence of a solid particle (CuSO4 5H2O) and a water droplet followed by dehydration using a carbon dioxide laser. The physical and chemical changes produced by the merging are traced in real time via complementary Raman, Fourier-transform infrared, and ultraviolet-visible spectrometers. This contactless manipulation of liquid droplets and solid particles may fundamentally change how scientists control and study chemical reactions relevant to, for example, combustion systems, material sciences, medicinal chemistry, planetary sciences, and biochemistry.

Controlled chemistry by the contactless merging of two droplets suspended in a single-axis acoustic levitator

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.