Analysis of Microdroplets and Microorganisms by Single Entity Electrochemistry

Single Entity Electrochemistry (SEE) is an emerging electrochemical technique that has been used to characterize discrete entities by measuring the change in current or potential during individual stochastic events (collision or adsorption) of an entity with an ultramicroelectrode (UME) of similar dimensions. The shape and magnitude of the SEE signal depend on the underlying mechanism of interaction with the UME surface. There is a critical need for quantitative models that correlate the SEE signal with properties of the entity-UME system, including effects of acquisition instrumentation, to prevent misinterpretation of data. This research focused on integrated experiments and simulations to quantify the effects of the interaction dynamics (collision and adsorption) of the microparticle and UME to deduce the properties of liquid droplets (diameter, contact radius, droplet redox mechanism) and bacteria (size, landing orientation, arrival pace). Chapter 1 introduces the SEE technique and the signals that appeared in the current vs. time graphs relevant to this dissertation. Chapter 2 compares the signal efficiency of adsorption versus bouncing collisions of emulsified ferrocene-trapped toluene droplets (~1 µm) with a disk UME of ~ 5 µm in diameter. Chapter 3 describes the size determination and adsorption orientation for three bacilli of variable length (~1, ~2, and ~5 µm)