Separation of chemical species impacts many areas of application such as purification of chemical products, sample preparation for clinical diagnostics, and water purification. In these applications, the goal is to isolate, enrich, or remove species selectively from a mixture. Many existing separation processes rely on physical interaction of chemical species with a solid support such as a filter, membrane, sorbent, or chromatographic packing to provide selectivity. These processes are widely used because they are highly effective. However, these solid supports can add unwanted weight and cost, undergo fouling (coating/clogging), and in some cases, require application of high pressures to accomplish their aim. The result is that the process becomes less affordable, durable, and portable, thereby limiting access. 

Alternatively, separations that leverage the electrostatic charge of target species to select and manipulate them can be accomplished with an electric field, which obviates the need for physical contact. These electrokinetic (EK) methods are readily miniaturized, lightweight, and low cost. However, persistent limitations have prevented their broad adoption. These include 1) an inability to process large volumes of fluid rapidly, 2) difficulty transporting enriched target species to a sensor or detector, 3) limited applicability to species with low or no electrostatic charge, and 4) decreased performance in the presence of high salt concentrations, such as in seawater or blood plasma.

The research work reported here sought to address these limitations. Specifically what was accomplished include the following. 1) Scale-up of an EK method to process larger volumes more rapidly. This was carried out using a porous electrode and packing material to stabilize fluid flow and prevent unwanted mixing. Importantly, the electrode and packing can be prevented from contacting the sample components that can cause fouling. 2) Creation of a new type of sensor that captures the target species on the packing material and detects its presence electrically. This approach enables separations for sample preparation and sensing in the same device, making it particularly relevant for diagnostics. 3) Development of a method to address target species with low/no charge. This method employs ionic (charged) surfactants to encapsulate the target species, thereby assigning it a charge that allows it to undergo separation. 4) A method to drive EK separations under high salt conditions (e.g., blood plasma). The method uses a modified device configuration to avoid applying the electric field in this high salinity medium.

The resulting devices and methods have provided the foundation for new technologies currently under development, including a point-of-care (POC) diagnostic device generalizable to many clinical applications and a low-cost, portable water desalting and purification unit. 

The project also indirectly contributed to the invention of a method to manipulate the content of water-in-oil droplets. This advancement has the potential to benefit biotechnologies that employ droplet microfluidics for both research and clinical applications. These applications include sensitive analyses of biomarkers with high diagnostic relevance.

The long-term outcome of this project will be greater access to rapid and sensitive diagnosis of infectious disease at home or in resource-limited settings, advances in clinical diagnostics that employ droplet biotechnologies, and clean drinking water in water-distressed regions or following natural disasters. Therefore, the potential impact of this research to human health and welfare is immense.

The educational objectives of this project have led to the development of materials to advance electrochemical education at the undergraduate level and to improve retention of underrepresented groups in the chemical enterprise. The project directly supported training of six graduate students (five female) and three undergraduates (all female), one of whom co-authored an article and continued to graduate school. 

Last Modified: 06/24/2024
Modified by: Robbyn Anand