Jaephil Do

On chip cell separator using magnetic bead-based enrichment and depletion of various surface markers.

This paper presents an on-chip magnetic cell sorting system for the sorting of cells based on a variety of surface markers. A polymer lab on a chip integrated with an electroplated array of Ni/Fe permalloy has been designed, fabricated, and characterized for the separation of cell substitutes at a variety of flow rates and incubation times. The system sequentially labels cell substitutes with magnetic beads and sorts them, repeating this process to sort for a variety of surface markers. Flow rates and incubation times were varied to characterize the system and produce the best combination of high specific capture and low nonspecific capture. The separation system developed on polymer is selective and efficient while being low cost, portable, and fabricated in a modular structure that can be integrated with other cell handling processes.

Low-cost magnetic interdigitated array on a plastic wafer

In this paper, a new magnetic interdigitated array (mIDA) has been designed, fabricated, and characterized for a magnetic bead separator on a plastic substrate, which can provide sampling capability in a low-cost disposable platform for magnetic bead-based biochemical detection systems. A mIDA was patterned and electroplated on a cyclic olefin copolymer (COC) substrate. To construct a magnetic bead sampler, an injection-molded microchannel layer on the COC was bonded over the mIDA using plastic thermal fusion bonding techniques. The microfabricated mIDA was excited using an external microelectromagnet to characterize the magnetic separator. Magnetic beads in a diameter of 2.0-9.0 /spl mu/m were successfully separated over the mIDA from an aqueous solution with magnetic beads at a flow rate of 3.0-7.0 /spl mu/l/min.

An On-Site Heavy Metal Analyzer With Polymer Lab-on-a-Chips for Continuous Sampling and Monitoring

An on-site analyzer system for monitoring of heavy metals has been presented. This analyzer can automatically perform long-term continuous water sampling and on-site heavy metals measurement using an array of disposable polymer lab-on-a-chips (lab chip) and a continuous flow sensing method. The system consists of a plastic fluidic motherboard with a microchannels network, microvalves and pump, control circuits, a wireless communication module, a potentiostat, LabVIEW control, and seven disposable heavy metal lab chips. Square wave anodic stripping voltammetry was performed using a microfabricated planar bismuth electrode on the chip for detecting heavy metal (e.g., cadmium, Cd) concentrations. Sensing performance sensitivity was improved with by the continuous flow sensing method propelled by the analyzer. On-site measurement of the Cd concentration change of the soil pore and ground water samples from a lab-scale reactor was automatically performed to evaluate the performance of the analyzer with lab chips.

The precise self-assembly of individual carbon nanotubes using magnetic capturing and fluidic alignment

A new method for the self-assembly of a carbon nanotube (CNT) using magnetic capturing and fluidic alignment has been developed and characterized in this work. In this new method, the residual iron (Fe) catalyst positioned at one end of the CNT was utilized as a self-assembly driver to attract and position the CNT, while the assembled CNT was aligned by the shear force induced from the fluid flow through the assembly channel. The self-assembly procedures were successfully developed and the electrical properties of the assembled multi-walled carbon nanotube (MWNT) and single-walled carbon nanotube (SWNT) were fully characterized. The new assembly method developed in this work shows its feasibility for the precise self-assembly of parallel CNTs for electronic devices and nanobiosensors.

Nanoinjection Lithography for Submicrometer Electrodes on Polymer Substrates

In this paper, a high-throughput method for fabricating submicrometer electrodes on polymer substrates is introduced and results are presented. This new process, known as nanoinjection lithography, combines nanoinjection molding with trench-filling techniques to create submicrometer electrodes on thermoplastic polymers. The fabrication method and resulting electrodes are characterized in this work using scanning electron microscopy, surface profilometry, and atomic force microscopy. The ability to fabricate submicrometer electrodes on polymer chips in a high-throughput process may allow the mass-production of ultrasensitive biosensors for point-of-care medical devices.

High precision fluidic alignment of carbon nanotubes using magnetic attraction on a metal catalyst

Precise self-assembly of carbon nanotubes (CNTs) by magnetic attraction on a catalyst and alignment by fluidic shear forces is reported in this work. The solution containing dispersed nanotubes was flowed in a microchannel and external magnetic field was applied by a permanent magnet for attracting a metal catalyst located at the end of the CNT. The assembly procedure and electrical characterization of the assembled nanotubes are presented and results are discussed. This work can provide a potential breakthrough for creating massively parallel CNT circuits for high performance nano electronic devices or nano biosensors.

High-Throughput Fabrication of Nanoelectrodes on Polymer using Nanoinjection and Trench-Filling Techniques

In this paper, high throughput fabrication of nanoelectrodes on polymer using nanoinjection and trench-filling techniques is developed and results are presented. The new fabrication method for producing nanoelectrodes on polymer substrates is characterized with scanning electron microscopy, surface profilometry, and atomic force microscopy. This method may be applied to mass-production of low-cost polymer biochips containing ultra-sensitive nanoelectrodes for biosensors in point-of-care medicine.

Hybrid Type On-Chip Magnetic Particle Separators for Accurate Positioning Magnetic Beads

The paper presents the development of a micromachined hybrid type magnetic particle separator, for accurate positioning of magnetic beads in two-dimensional array, using a magnetic interconnection technique between permalloy microstructures and external electromagnets. The developed magnetic particle separator generates relatively large magnetic force on magnetic particles (or beads) with a simple structure and low power consumption. The developed device has no heat problems because the electromagnets are isolated from the sites where magnetic particle separation takes place. In addition accurate positioning of magnetic particles in 2-dimesional array patterns can be achieved.