Pneumatically-driven elastomeric devices for a programmable lab on a chip and applications
Abstract
This dissertation presents two programmable lab-on-a-chip (PLoC) systems based on pneumatically-driven elastomeric devices for continuous-flow microfluidics and optoelectrowetting (OEW) for digital microfluidics, respectively. The successful development of the systems drastically reduces cost, simplifies fabrications, and provides a general-purpose platform for multi-biochemical assays. The novelties of this research are (i) a complete PDMS-based PLoC system integrating all microfluidic components, (ii) programmability for microfluidic chips, and (iii) open configuration, module extensible, on-chip electrostatic actuation utilizing OEW. To create the aforementioned PDMS-based pneumatically-driven system, various microfluidic components, such as valves, pumps, sensors, and so on, need to be fully integrated and characterized. Flow visualization was used to quantify the microfluidic behaviors in the microchannels. The valve was designed based on the concept of Mathies' valve [1]. The pump was composed of three individual valves, enabling a peristaltic motion for programmable fluid actuation. Three indices, including diodicity (Ddiode), oscillation number (O), and output efficiency (η), were proposed to quantify the performance out of three widely-used pump sequences. Some vital operations, such as heating, sensing, and mixing were also studied using the established platform. All of the processes eventually contribute to a PLoC chip for various assays. Depending on the programmability, more assays can be conducted by editing a computer script based on a self-developed program architecture, named Aquacore Instruction Set (AIS). The broader impact is the realization of a programmable and integrated microfluidic chip for multi-biochemical assays. In addition to the highly integrated microfluidic PLoC chip, an emerging research field highlighting 'lab in a drop' was developed in this dissertation as well. By incorporating a photoconductive layer into a conventional electrowetting chip, i.e., electrowetting on dielectric (EWOD), the chip is capable of manipulating droplets with light. Droplet translation is achieved by a series of complex energy conversions. The integration realizes dynamic and rapid droplet handling, which eventually will enable programmable lab-in-a-drop assays. To enhance the extensibility of the chip, coplanar and interdigitated electrodes were used to enable an open configuration. Contrary to the usual sandwiched device, the open configuration allows much more access to the droplets for pipetting samples on and off the chip. An application integrating the open OEW (O-OEW) chip with optoelectric forces to perform multiscale manipulation was conducted. A liquid droplet containing micro particles was first translated from one site to the target spot by a broadband illumination source and then the suspended particles were concentrated with a highly-focused IR (1064 nm) laser beam combined with the electric field. The demonstration showed a successful manipulation of two different sized objects covering a wide range of length scales—from several millimeters to submicrometers. Overall, a PDMS-based PLoC chip has been completely developed including designs, fabrications, characterizations, and applications. The complete automation of cyclic particle extraction and glucose detection shows the promise of the device for more assays. Furthermore, preliminary characterizations of thermal cycling and capillary electrophoresis (CE) were performed in the chip for future polymerase chain reaction (PCR). An innovative droplet handling technique, O-OEW, which shows more potential in programmable manipulation, was developed. Despite the early stage of its development, O-OEW shows promise to revolutionize the face of next generation microdfluidics in the near future.
Degree
Ph.D.
Advisors
Wereley, Purdue University.
Subject Area
Biomedical engineering|Electrical engineering|Mechanical engineering
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