Microfluidic devices for high-throughput plant phenotyping and bioenergy harvesting from microbes and living plants

Abstract

<p>Microfluidics and micro/nanofabrication techniques provide powerful technological platforms to develop miniature bioassay devices for studying cellular and multicellular organisms. Microfluidic devices have many advantages over traditional counterparts, including good throughput due to parallel experiments, low infrastructural cost, fast reaction, reduced consumption of agent and reagent, and avoidance of contamination. This thesis is focused on the development of a microfluidic toolkit with several miniature devices to tackle important problems that the fields of plant phenotyping and bioenergy harvesting are facing. The ultimate goal of this research is to realize high-throughput screening methods for studying environment-genomics of plants through phenomics, and understanding microbial and plant metabolisms that contribute to harvesting bioenergy from microbes and living plants in different environments.</p> <p>First, we develop vertical microfluidic plant chips and miniature greenhouses for high throughput phenotyping of Arabidopsis plants. The vertical design allows for gravitropic growth of multiple plants and continuous monitoring of seed germination and plant development at both the whole-plant and cellular levels. An automatic seed trapping method is developed to facilitate seed loading process. Also, electrospun nanofibrous membranes are incorporated with a seed germination chip to obtain a set of incubation temperatures on the device. Furthermore, miniature greenhouses are designed to house the plant and seed chips and to flexibly change temperature and light conditions for high-throughput plant phenotyping on a multi-scale level.</p> <p>Second, to screen bacteria and mutants for elucidating mechanisms of electricity generation, we develop two types of miniature microbial fuel cells (µMFCs) using conductive poly(3,4-ethylenedioxythiophene) nanofibers and porous graphene foam (GF) as three-dimensional (3D) anode materials. It is demonstrated that in the nanofiber-based µMFC, the nanofibers are suitable for rapid electron transfer and Shewanella oneidensis can fully colonize the interior region of the nanofibers. The GF-based µMFC is featured with a porous anolyte chamber formed by embedding a GF anode inside a microchannel. The interconnected pores of the GF provide 3D scaffolds favorable for cell attachment, inoculation and colonization, and more importantly, allow flowing nutritional and bacterial media throughout the anode with minimal waste. Therefore, the nutrients in bio-convertible substrates can be efficiently used by microbes for sustainable production of electrons.</p> <p>Last, we develop a first miniature plant-MFC or µPMFC device as a technological interface to study bioenergy harvesting from microbes and living plants. A pilot research is conducted to create the µPMFC device by sandwiching a hydrophilic semi-permeable membrane between a µMFC and a plant growth chamber. Mass transport of carbon-containing organic exudates from the plant roots to the µMFC is quantified. This work represents an important step towards screening plants, microbes, and their mutants to maximize energy generation of PMFCs.</p>