Microfluidic Assays to Enhance Biodetection and Diabetes Research

Expansion of biomarker detections with nuanced monitoring of disease states can deliver more effective, personalized medicine. Leveraging novel biomarkers in clinical settings requires higher sensitivity, shorter assay times, and increased specificity in protein detection. Standard ELISA involves multi-step preparations that extends the length and complexity of its protocol. Newer techniques using nanoplasmonics, fluorescence resonance energy transfer, single molecule detections, among others require specialized equipment and techniques. Here I report a novel method using immuno-functionalized, porous poly (ethylene) glycol diacrylate (PEGDA) hydrogel microspheres to enable rapid, high sensitivity antigen detection in arrayed microfluidics. I applied these microfluidic techniques to wound healing and diabetes motivated applications that illustrate their future potentials. In wound healing, Vascular endothelial growth factor (VEGF) promotes wound revascularization by stimulating angiogenesis, in addition to stimulatory effects on other wound cells. In our arrayed microfluidics, the technique incorporates antibody encapsulation, trapping, and flow perfusion on a single device to allow an integrated assay. The result showed that the convergence of tunable porous hydrogel with efficient microfluidics improved the sensitivity of the assay. The detection limit of this microfluidic porous microgel based assay was 0.9 pg/mL, with only 1+ hour of assay time, demonstrating a novel assay that exceed conventional technologies in terms of sensitivity and speed. In the multifaceted disease of diabetes, sensitive, single volume detections of multiple antibodies can provide immunoprofiling and early screening of at-risk patients. To advance the state-of-the-art suspension assays for diabetes antibodies, porous hydrogel droplets were multiplexed in microfluidic serpentine arrays to enhance the detection of antibodies against insulin, glutamic acid decarboxylase (GAD), and insulinoma-associated protein 2 (IA-2). Optimization of assay protocol resulted in a shortened assay time of 2 h, with better than 20 pg mL detection limits across all three antibodies. Specificity and cross-reactivity tests showed negligible background, nonspecific antibody–antigen, and nonspecific antibody–antibody bindings. Multiplexed detections were able to measure within 15% of target concentrations at both low and high ranges. The technique enabled quantifications of as little as 8000 molecules in each 500 μm droplet using a single volume, multiplexed assay format, a breakthrough necessary for the adoption of diabetes panels for clinical screening and monitoring in the future. Also, the PEGDA hydrogel sensors is being applied in our latest diabetes project: Hypoxia-FFA synergy in beta cell impairment via multimodal microfluidics. To achieve the beta cell culture and precise detection of insulin, a porous PEGDA hydrogel biosensor thin film was developed for coating on microfluidic devices. This new spatial sensor is able to enhance the detection of secreted insulin transport, while mapping their release in beta cells cultured atop a gradient of oxygen concentrations. The optimization of this multimodal device resulted in a 200 um thickness sensor, shorten assay time of 2 hours, better than 50 pg/mL detection limits, and capable of sustaining better than 90% viability of beta cells.Master of Science in EngineeringBioengineering, College of Engineering and Computer ScienceUniversity of Michigan-Dearbornhttps://deepblue.lib.umich.edu/bitstream/2027.42/143525/1/Microfluidic Assays to Enhance Biodetection and Diabetes Research (Kai Duan).pdfDescription of Microfluidic Assays to Enhance Biodetection and Diabetes Research (Kai Duan).pdf : Thesi

Wireless Power Transfer and Data Collection in Wireless Sensor Networks

In a rechargeable wireless sensor network, the data packets are generated by sensor nodes at a specific data rate, and transmitted to a base station. Moreover, the base station transfers power to the nodes by using Wireless Power Transfer (WPT) to extend their battery life. However, inadequately scheduling WPT and data collection causes some of the nodes to drain their battery and have their data buffer overflow, while the other nodes waste their harvested energy, which is more than they need to transmit their packets. In this paper, we investigate a novel optimal scheduling strategy, called EHMDP, aiming to minimize data packet loss from a network of sensor nodes in terms of the nodes' energy consumption and data queue state information. The scheduling problem is first formulated by a centralized MDP model, assuming that the complete states of each node are well known by the base station. This presents the upper bound of the data that can be collected in a rechargeable wireless sensor network. Next, we relax the assumption of the availability of full state information so that the data transmission and WPT can be semi-decentralized. The simulation results show that, in terms of network throughput and packet loss rate, the proposed algorithm significantly improves the network performance.Comment: 30 pages, 8 figures, accepted to IEEE Transactions on Vehicular Technolog

Type-II quadrupole topological insulators

Modern theory of electric polarization is formulated by the Berry phase, which, when quantized, leads to topological phases of matter. Such a formulation has recently been extended to higher electric multipole moments, through the discovery of the so-called quadupole topological insulator. It has been established by a classical electromagnetic theory that in a two-dimensional material the quantized properties for the quadupole topological insulator should satisfy a basic relation. Here we discover a new type of quadrupole topological insulator (dubbed type-II) that violates this relation due to the breakdown of the correspondence that a Wannier band and an edge energy spectrum close their gaps simultaneously. We find that, similar to the previously discovered (referred to as type-I) quadrupole topological insulator, the type-II hosts topologically protected corner states carrying fractional corner charges. However, the edge polarizations only occur at a pair of boundaries in the type-II insulating phase, leading to the violation of the classical constraint. We demonstrate that such new topological phenomena can appear from quench dynamics in non-equilibrium systems, which can be experimentally observed in ultracold atomic gases. We also propose an experimental scheme with electric circuits to realize such a new topological phase of matter. The existence of the new topological insulating phase means that new multipole topological insulators with distinct properties can exist in broader contexts beyond classical constraints.Comment: 32 pages, 17 figure