Development of the constrained drop surfactometer

Abstract

Measurements of surface tension and contact angle are important for a broad range of industrial and scientific areas, such as soap and detergent, spray and coating, and lung surfactant. In this thesis, a novel experimental methodology called the constrained drop surfactometer (CDS) was developed for measuring surface tension and contact angle based on drop shape analysis. Both hardware and software were developed for the CDS. We first demonstrated the feasibility of the CDS in determining air-liquid surface tension and liquid-liquid interfacial tension by analyzing different drop/bubble configurations, including the constrained sessile drop, pendant drop, constrained pendant drop, and pendant bubble. We then showed the capacity of the CDS in determining the low-rate dynamic contact angle on a solid surface. Finally, we have engaged the CDS in two original scientific researches. In the first research, we used the CDS as a miniaturized Langmuir film balance for studying phase transitions at a DPPC monolayer. In the second research, we used the CDS as a Gibbs surfactometer for in vitro simulating biophysical properties of natural lung surfactants extracted from animals. All studies successfully demonstrated the feasibility, simplicity, accuracy, and versatility of the CDS.