Studying kinetics of a surface reaction using elastocapillary effect.

Area of Science:

• Microfluidics
• Materials Science
• Surface Chemistry

Background:

• Microfluidic channels made of poly(dimethylsiloxane) (PDMS) deform when liquids are introduced due to changes in solid-liquid interfacial energy, a phenomenon known as the elastocapillary effect.
• The evolution of new species at the solid-liquid interface alters interfacial energy, influencing channel deformation.
• This deformation can be measured optically, suggesting its potential for monitoring interfacial events.

Purpose of the Study:

• To investigate the potential of the elastocapillary effect for monitoring physical and chemical processes occurring at solid-liquid interfaces within microfluidic channels.
• To establish a correlation between channel wall deformation and the kinetics of interfacial events.

Main Methods:

• Microfluidic channels fabricated from PDMS were used.
• The deformation of the channel walls was measured in real-time using an optical profilometer.
• Reactions involving aqueous metal salt solutions with PDMS and physical adsorption of Bovine Serum Albumin (BSA) were studied.

Main Results:

• The kinetics of metallic nanoparticle formation via reaction of metal salts with PDMS were captured by monitoring wall deformation.
• The physical adsorption of BSA on the PDMS surface was also monitored through wall deformation.
• The rate of deformation change was correlated with the rate of these processes, allowing for the extraction of reaction rate constants.

Conclusions:

• The elastocapillary effect serves as a viable analytical tool for in-situ monitoring of physical and chemical processes.
• This method is particularly useful for processes where the reaction site is not accessible to conventional analytical techniques.
• Real-time monitoring of interfacial dynamics is achievable through precise measurement of microfluidic channel deformation.