Polymer based microfabrication and its applications in optical MEMS and bioMEMS

Due to its ease of fabrication, low cost and great variety of functionalities, polymer has become an important material in microfabrication. MEMS devices with polymer as the structure material have found applications in various fields, especially in BioMEMS and optical MEMS. In this dissertation, three polymer based microfabricated devices/components have been developed and tested. Various polymer based fabrication techniques, such as high aspect ratio SU-8 photolithography, three dimensional polydimethylsiloxane (PDMS) soft lithography, multi-layer soft lithography and PDMS double casting technique have been developed/studied and employed in the device fabrication process. The main contribution of this dissertation includes: (1) Developed two novel methods for the fabrication of out-of-plane microlens. The PDMS and UV curable polymer (NOA73) replication technique made possible the fast replication of out-of-plane microlens and broaden the lens material selection. The in-situ pneumatical microlens fabrication technique, on the other hand, provides feasible method to integrate out-of-plane microlens into microfluidic chips requiring minimal design footprint and fabrication complexity. (2) Design, fabrication and test of a microchip flow cytometer with 3-D hydrofocusing chamber and integrated out-of-plane microlens as on-chip optical detection component. The developed micro flow cytometer offers 3-D hydrofocusing like conventional cytometer cuvette, and has on-chip microlens for optical signal collection to improve the detection efficiency. With the latest design improvement, the hydrofocusing chamber can focus the sample stream down to less than 10 m in diameter in both vertical and horizontal directions. (3) Development of a PDMS microchip based platform for multiplex immunoassay applications. Integrated micro valves were employed for manipulation of fluidic reagents in the microchannel network. PDMS surface was used as the solid phase substrate for immuno-reactions. Preliminary results showed that, even with low cost polyclonal goat anti-mouse IgG as the reporter antibody, the detection limit of goat mouse IgG can reach as low as 5 ng/mL (about 33 pM). With the continuous advance in microfabrcation technique and polymer science, polymer based microfabrication and polymer MEMS devices will keep to evolve. In the future, more work needs to be done in this field with great potential and endless innovations

Advances in 3D Neural Stylization: A Survey

Modern artificial intelligence provides a novel way of producing digital art in styles. The expressive power of neural networks enables the realm of visual style transfer methods, which can be used to edit images, videos, and 3D data to make them more artistic and diverse. This paper reports on recent advances in neural stylization for 3D data. We provide a taxonomy for neural stylization by considering several important design choices, including scene representation, guidance data, optimization strategies, and output styles. Building on such taxonomy, our survey first revisits the background of neural stylization on 2D images, and then provides in-depth discussions on recent neural stylization methods for 3D data, where we also provide a mini-benchmark on artistic stylization methods. Based on the insights gained from the survey, we then discuss open challenges, future research, and potential applications and impacts of neural stylization.Comment: 26 page

Design, fabrication and test of a pneumatically controlled, renewable, microfluidic bead trapping device for sequential injection analysis applications

This paper describes the design, fabrication, and testing of a pneumatically controlled, renewable, microfluidic device for conducting bead-based assays in an automated sequential injection analysis system. The device used a brick wall -like pillar array (pillar size: 20 μm length × 50 μm width × 45 μm height) with 5 μm gaps between the pillars serving as the micro filter. The flow channel where bead trapping occurred is 500 μm wide × 75 μm deep. An elastomeric membrane and an air chamber were located underneath the flow channel. By applying pressure to the air chamber, the membrane is deformed and pushed upward against the filter structure. This effectively traps beads larger than 5 μm and creates a bed or micro column of beads that can be perfused and washed with liquid samples and reagents. Upon completion of the assay process, the pressure is released and the beads are flushed out from underneath the filter structure to renew the device. Mouse IgG was used as a model analyte to test the feasibility of using the proposed device for immunoassay applications. Resulting microbeads from an on-chip fluorescent immunoassay were individually examined using flow cytometry. The results show that the fluorescence signal intensity distribution is fairly narrow indicating high chemical reaction uniformity among the beads population. Electrochemical on-chip assay was also conducted. A detection limit of 1 ppb was achieved and good device reliability and repeatability were demonstrated. The novel microfluidic-based beads-trapping device thus opens up a new pathway to design micro-bead based immunoassays for various applications

4-aminobenzylphosphonic acid-modified glassy carbon electrode for electrochemically sensing paracetamol

4-Aminobenzylphosphonic acid (4-ABPA) was covalently immobilized on a glassy carbon electrode (GCE) surface via an electrochemical oxidation process. The bare and 4-ABPA-modified GCEs were employed to sense paracetamol (PCT) in a series of buffer solutions with different pH values at 36.8 C for comparison. The results showed that the 4-ABPA-modified GCE was more stable with higher electrochemical sensitivity toward PCT than the unmodified one. Moreover, the 4-ABPA-modified GCE can be used to monitor in-vitro dissolution process of PCT-loaded electrospun poly(vinyl alcohol) (PVA) nanofiber systems in real time

Intersectin links WNK kinases to endocytosis of ROMK1

With-no-lysine (WNK) kinases are a novel family of protein kinases characterized by an atypical placement of the catalytic lysine. Mutations of 2 family members, WNK1 and WNK4, cause pseudohypoaldosteronism type 2 (PHA2), an autosomal-dominant disease characterized by hypertension and hyperkalemia. WNK1 and WNK4 stimulate clathrin-dependent endocytosis of renal outer medullar potassium 1 (ROMK1), and PHA2-causing mutations of WNK4 increase the endocytosis. How WNKs stimulate endocytosis of ROMK1 and how mutations of WNK4 increase the endocytosis are unknown. Intersectin (ITSN) is a multimodular endocytic scaffold protein. Here we show that WNK1 and WNK4 interacted with ITSN and that the interactions were crucial for stimulation of endocytosis of ROMK1 by WNKs. The stimulation of endocytosis of ROMK1 by WNK1 and WNK4 required specific proline-rich motifs of WNKs, but did not require their kinase activity. WNK4 interacted with ROMK1 as well as with ITSN. Disease-causing WNK4 mutations enhanced interactions of WNK4 with ITSN and ROMK1, leading to increased endocytosis of ROMK1. These results provide a molecular mechanism for stimulation of endocytosis of ROMK1 by WNK kinases