Michael J. Rust

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.

Rapid Fabrication of a Nano Interdigitated Array Electrode and its Amperometric Characterization as an Electrochemical Sensor

Nano interdigitated array (IDA) electrodes (electrode finger width = 100 nm; finger spacing = 200 nm; surface area = 0.2 mm2) have been fabricated and characterized amperometrically for the electrochemical detection of the concentrations of reversible redox species. Using p-aminophenol as the redox species, a detection limit of 10 pM of the species concentration has been achieved. This detection limit is three orders of magnitude lower than the micro IDA counterpart that has been reported to date, proving the enhanced redox cycling at the nano IDA electrodes. Using a higher electron dose, the proximity effect of the electron beam in the e-beam lithography process has been utilized to reduce the duration of the nano IDA pattern transfer step to less than 30 minutes. This makes it possible to fabricate the entire sensor within a day, including the electrode metal evaporation, metal lift-off and electroplating of reference electrode.

Simple passive micromixer using recombinant multiple flow streams

A passive microfluidic mixer with high performance is designed and fabricated in this work. Diamond-shaped obstacles were chosen to split the flow into several streams, which are then guided back together after the obstacle. To keep pressure drop low, the channel cross-sectional area was maintained equal to the input cross-sectional area, and this was held constant throughout the device. The proposed design was modeled using computational fluid dynamics (CFD) software. The effects of channel width, channel length, location of obstructions, and Reynolds Number (Re) were investigated. The simulated results were verified experimentally. Simulation data showed that the designed micromixer achieved 90% mixing at a channel length of 4.35 mm with pressure drop of 584 Pa at Re = 1, while experimental data for Re = 0.1 showed 90% mixing at 7 mm. The mixer functions well especially at the low Re (Re = 0.1).

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.

Work in Progress: Introducing Electrical and Computer Engineering to High School Math and Science Students

This paper describes the recent activities of electrical and computer engineering doctoral students in the design, development, and implementation of lessons for high school mathematics and science classes. The graduate students, called fellows, worked in secondary classrooms in the Cincinnati Public Schools District as a part of Project STEP at the University of Cincinnati, which is funded by the National Science Foundation GK-12 Program. The fellows formed partnerships with secondary math and science teachers to generate new lessons, activities, and resources to enhance the STEM skills of high school students. Additionally, the Fellows used their engineering expertise to bring authentic learning experiences into the classroom and introduced concepts in their field of engineering to underserved student populations. This paper discusses observations and reflections by the fellows regarding aspects of the activities that had the most impact on student learning and interest in engineering, which was measured by self-reported student surveys

Assembly of Nanoparticles and Nanoelectrodes on Nanoinjection Molded Polymer Templates

This paper presents a mass-producible method for fabricating nanoparticle assemblies and nanoelectrodes using nanoinjection molded polymer templates. Results are demonstrated for assembly of silica nanoparticles and silver nanoelectrodes on cyclic olefin copolymers (COC) with 375 nm resolution. This method offers an innovative low-cost, high-throughput approach to nano-scale assembly for applications in photonic, electronic and biomedical devices.

Interdigitated Array Electrodes with Nano Gaps Using Optical Lithography and Controlled Undercut Method

Interdigitated array (IDA) electrodes with nano-gaps were fabricated using a newly developed optical lithography and controlled undercut method. Nano gaps of 250 nm between electrodes were developed while maintaining a large electrode area. The developed electrodes with nano gaps were applied as an electrochemical biosensor for the detection of poly-aminophenol (PAP) with 10-7 M detection limit. This method may enable the mass-production of disposable biosensors based on the nano-gap IDA electrodes.

It's a nano world after all

The nanotechnology module was designed to introduce nanotechnology and the ideas behind it to students who know little about the subject. Students participate In hands-on activities that give them a better sense of how small the nano world really is, and to learn about the various applications of nanotechnology at the same time.

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.