Optomechanical measurement of single nanodroplet evaporation with millisecond time-resolution

Abstract

Tracking the evolution of an individual nanodroplet of liquid in real-time remains an outstanding challenge. Here a miniature optomechanical resonator detects a single nanodroplet landing on a surface and measures its subsequent evaporation down to a volume of twenty attoliters. The ultra-high mechanical frequency and sensitivity of the device enable a time resolution below the millisecond, sufficient to resolve the fast evaporation dynamics under ambient conditions. Using the device dual optical and mechanical capability, we determine the evaporation in the first ten milliseconds to occur at constant contact radius with a dynamics ruled by the mere Kelvin effect, producing evaporation despite a saturated surrounding gas. Over the following hundred of milliseconds, the droplet further shrinks while being accompanied by the spreading of an underlying puddle. In the final steady-state after evaporation, an extended thin liquid film is stabilized on the surface. Our optomechanical technique opens the unique possibility of monitoring all these stages in real-time.

Free-access optomechanical liquid probes using a twin-microbottle resonator

“…Moreover, such a stable frequency estimation capability enables us to perform cavity optomechanical sensing, i.e., measuring the frequency shift of mechanical resonance via the high-Q optical resonance. This technique has been utilized in various sensor applications, such as accelerometers [2], magnetometers [3], [4], chemical sensors [5], and biochemical sensors [6]- [9].…”

Ultrasonic spectroscopy of sessile droplets coupled to optomechanical sensors

“…As evidenced by the microscope images in Fig. 5(a), and not uncommonly, 25 these droplets remained essentially pinned at a fixed base diameter over the entire monitored period (several hours) of evaporation. The estimated fundamental breathing mode frequency and volume of the droplet were recorded at intervals, with the results shown in Fig.…”

Nanomechanical Sensing for Mass Flow Control in Nanowire-Based Open Nanofluidic Systems

“…In this work we demonstrate the integration of electrically driven liquid transport with nanomechanical flow rate sensing for mass flow control in open nanofluidic systems. Nanomechanics has been fruitfully combined before with fluidic technologies in a variety of contexts, from buoyant mass detection of bioanalytes − to ultralow volume liquid handling − or surface wettability and evaporation dynamics research. , Our approach for mass flow control relies on the combination of free-standing open nanofluidic channels with frequency shift tracking of the flexural resonances of beam resonators that integrate these channels. We prove this approach by two complementary implementations: In one, nanowire (NW) open channels are assembled with microcantilever (MC) resonators so that each component provides separate functionality, either liquid transport or mass sensing, respectively; in another, NWs operate simultaneously as open channels and flexural resonators, providing dual functionality.…”