Su Eun Chung

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.

Optofluidic maskless lithography system for real-time synthesis of photopolymerized microstructures in microfluidic channels

The authors propose an optofluidic maskless lithography technique that can dynamically synthesize free-floating polymeric microstructures inside microfluidic channels by selectively polymerizing photocurable resin with high-speed two-dimensional spatial light modulators. The combination of programable optical projection and microfluidic devices allows one to precisely control the timing and location of the photopolymerization process for microstructure fabrication. Real-time generation of microparticles with various shapes, sizes, ordering, and material contents are experimentally demonstrated. Long polymeric structures of which size is not limited by the exposure field of view can also be fabricated.

Three‐Dimensional Fluidic Self‐Assembly by Axis Translation of Two‐Dimensionally Fabricated Microcomponents in Railed Microfluidics

A method for high-throughput 3D self-assembly of 2D photopatterned microstructures using railed microfluidics is presented. Vertical device patterning of heterogeneous materials requires high-level integration using conventional microelectromechanical system (MEMS) technology; however, 3D railed assembly enables easy and fast self-assembly via a fluidic axis-translation process and simple material exchange in microfluidic channels. Individually photopatterned 2D microstructures are axis-translated from in-plane to out-of-plane and fluidically self-assembled, guided by side-rails in microfluidic channels to form a 3D morphology. Since the structures are fabricated in fluidic environments, there are no fixed initial points on the channel substrate allowing fluidic horizontal stacking of erected 2D structures. The guiding mechanism of railed microfluidics enables efficient fluidic handling and deterministic 3D self-assembly of heterogeneous components such as electronic components or polymeric microstructures using only fluidic force.

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.

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.

Synthesis of photopolymerized microstructures in microfluidic channels for smart scalable systems

We introduce dasiaoptofluidic maskless lithography systempsila that can dynamically synthesize free-floating polymeric microstructures inside microfluidic channels with high-speed two-dimensional spatial light modulators, and propose dasiarailed microfluidics,psila an agile method to guide and assemble microstructures inside fluidic channels.

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.