Jiyun Kim

Colour-barcoded magnetic microparticles for multiplexed bioassays

Encoded particles have a demonstrated value for multiplexed high-throughput bioassays such as drug discovery and clinical diagnostics. In diverse samples, the ability to use a large number of distinct identification codes on assay particles is important to increase throughput. Proper handling schemes are also needed to readout these codes on free-floating probe microparticles. Here we create vivid, free-floating structural coloured particles with multi-axis rotational control using a colour-tunable magnetic material and a new printing method. Our colour-barcoded magnetic microparticles offer a coding capacity easily into the billions with distinct magnetic handling capabilities including active positioning for code readouts and active stirring for improved reaction kinetics in microscale environments. A DNA hybridization assay is done using the colour-barcoded magnetic microparticles to demonstrate multiplexing capabilities.

Programming magnetic anisotropy in polymeric microactuators

Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion.

In Situ Fabrication and Actuation of Polymer Magnetic Microstructures

We demonstrate a single-exposure in situ magnetic actuator fabrication technique using magnetic nanoparticles (MNs) containing UV curable polymer in a Polydimethylsiloxane (PDMS) channel. Microstructures with a 3-D anchored cantilever as well as free-floating components are fabricated in a single step at a single site without the use of a sacrificial layer. By controlling the location of high oxygen concentration area through PDMS substrate patterning, we can create partially bound and free-floating movement-restricted structures. This allows us to create complex magnetic actuators, such as a 3-D anchored cantilever, motor type, and rail-guided magnetic actuators. The actuating performance of UV photopatterned magnetic microstructures depends on the MN concentration in photopolymer resin and magnetic field intensity. The measured translational velocity of magnetic microactuators with a 1 : 10 MN concentration is 140 μm/s under 1400 G of magnetic field in poly(ethylene glycol) diacrylate resin. Also, we demonstrate selective magnetic actuation of heterogeneous structures composed of magnetic and nonmagnetic parts self-assembled in railed microfluidic channels. Only magnetic parts from the assembly selectively actuated due to the magnetic field without response to the flow. Therefore, we have developed a versatile magnetic microstructure fabrication method that is very simple and fast, enabling rapid in situ fabrication and actuation.

Magnetochromatic Microactuators for a Micropixellated Color‐Changing Surface

A magnetically tunable chromatic nanocomposite microactuator is proposed, which utilizes the optical and magnetic behaviors of self-assembled super-paramagnetic nanoparticles fixed in a polymeric microstructure. The original color can be programmed during a simple photolithography process, and the color can be changed just by applying and changing an external magnetic field. These microactuators are capable of acting as pixels in a color-changing pattern.

Fiber composite slices for multiplexed immunoassays

Fabrication methods for the development of multiplexed immunoassay platforms primarily depend on the individual functionalization of reaction chambers to achieve a heterogeneous reacting substrate composition, which increases the overall manufacturing time and cost. Here, we describe a new type of low-cost fabrication method for a scalable immunoassay platform based on cotton threads. The manufacturing process involves the fabrication of functionalized fibers and the arrangement of these fibers into a bundle; this bundle is then sectioned to make microarray-like particles with a predefined surface architecture. With these sections, composed of heterogeneous thread fragments with different types of antibodies, we demonstrated quantitative and 7-plex immunoassays. We expect that this methodology will prove to be a versatile, low-cost, and highly scalable method for the fabrication of multiplexed bioassay platforms.

Micro-pixellated blue/brown color changing surface using magnetically actuated nanocomposite actuators

We propose a new magnetically tunable color changing material and its operation method which enable both color generation and change within a single material. To achieve this, we fabricated micro-sized magnetic nanocomposite actuators for a single color changing unit and assembled them on the substrate. This method offers very simple fabrication and operation of color changing surface with high resolution.

Optofluidic in-situ fabrication of magnetic actuators in microfluidic channels

We demonstrate in-situ fabrication of magnetic actuators using optofluidic maskless lithography (OFML). Photopatterning of magnetic structures in same place with actuation area reduces extra steps for transportation from the fabrication site to actuation site.

Fluidic manipulation and self-assembly of microdevices in railed microfluidic channels

We demonstrate fluidic manipulation and assembly of silicon microchips by creatively combining railed microfluidics and computer-vision aided dynamic chip packaging. Externally fabricated silicon microchips are fluidically guided and self-assembled, potentially enabling low cost fluidic packaging of integrated circuits.