Adsorbed microdroplets are mobile at the nanoscale

Area of Science:

• Physical Chemistry
• Nanotechnology
• Electrochemistry

Background:

• Microdroplets display unique reactivity at multiphase boundaries.
• The mobility of sessile microdroplets, a potential driver of this reactivity, remains poorly understood.
• Investigating nanoscale droplet motion is crucial for understanding interfacial phenomena.

Purpose of the Study:

• To determine if adsorbed microdroplets can exhibit mobility at the nanoscale.
• To develop a sensitive method for detecting nanometric motions of insulating droplets on electrified interfaces.

Main Methods:

• Placing an organic droplet on a microelectrode within an aqueous phase.
• Monitoring droplet dissolution via a heterogeneous reaction and tracking current changes.
• Utilizing finite element modeling to analyze current transients and three-phase boundary movement.

Main Results:

• Abrupt changes in current were observed as the droplet's contact radius neared the microelectrode size.
• Finite element modeling confirmed these steps correspond to nanometric movements of the three-phase boundary.
• Estimated velocities of the liquid interface ranged from tens to hundreds of nanometers per second.

Conclusions:

• Adsorbed microdroplets demonstrate measurable nanoscale mobility.
• Interfacial processes involving contact electrification and friction may occur even in seemingly static droplets.
• The findings open new avenues for studying microdroplet dynamics and interfacial reactions.