1993 OURE report, including the 3rd Annual UMR Undergraduate Research Symposium -- Entire Proceedings

The Opportunities for Undergraduate Research Experience program began in 1990. This volume represents the proceedings of the third annual OURE program. The aims of the program are to enrich the learning process and make it more active, encourage interaction between students and faculty members, raise the level of research on the campus, help recruit superior students to the graduate program, and support the notion that teaching and research are compatible and mutually reinforcing. As the papers herein attest, the OURE program continues to achieve its goals -- UMR students have performed research on an enormous variety of topics, have worked closely with faculty members, and have experienced deeply both the pleasures and frustrations of research. Several of the undergraduates whose papers are included are now graduate students at UMR or elsewhere. The first section of this volume is made up of papers presented at the third annual UMR Undergraduate Research Symposium held on January 29, 1993

Controlled structures and properties of single-walled carbon nanotubes custom-produced by chemical vapor deposition method.

Single walled carbon nanotubes (SWNT) are considered as one of the most promising nanomaterials for a large variety of applications that require SWNTs with controlled structures and properties, which is the main focus of this dissertation. The first approach to tackle this problem is to develop appropriate methods to synthesize SWNTs of controlled structure. To achieve this goal, a number of techniques have been developed to selectively grow SWNTs on different support from porous silica to flat substrates. It is demonstrated that a precise control over chirality, diameter and bundle size can be obtained by tuning the reaction temperature in the growth of SWNT over Co-Mo/silica powder by CO disproportionation. In addition, a novel method for selective growth of SWNT on flat substrates has been developed. In this method, SWNTs can be grown either in random direction or vertical alignment on the surface under standard CoMoCATRTM reaction conditions. The second trust of this dissertation is to investigate the properties of as-produced SWNTS with their controlled structural parameters (i.e., diameter, bundle size, chirality, and alignment). Field emission measurements have been conducted to evaluate the dependence of the emission characteristics on the SWNT structure. For the nanotubes grown on flat substrates, the response of the vertically aligned SWNT to polarization of both X-rays (in XANES) and visible light (in Raman) clearly revealed the anisotropic optical properties of V-SWNT. Finally, efforts have been made to explore the growth mechanism of VSWNT on flat substrate. X-ray photoelectron spectroscopy and atomic force microscopy conducted on the flat surface with deposited catalyst gave detailed information about the chemical status of Co-Mo catalyst and their morphological distribution. The evolution of the growth of VSWNT with time was visualized by scanning electron the chemical status of Co-Mo catalyst and their morphological distribution. The evolution of the growth of VSWNT with time was visualized by scanning electron microscopy and clearly demonstrated a two-step process involving the formation of a crust layer followed by a concerted growth constrained by crust. Then a kinetic study with fitted growth data has been derived and the maximum growth rate estimated (i.e. 12.5 nm/sec). In addition to the growth of VSWNT, oxidation and transferring of VSWNT has been investigated for future applications

[Research Pertaining to Physics, Space Sciences, Computer Systems, Information Processing, and Control Systems]

Research project reports pertaining to physics, space sciences, computer systems, information processing, and control system

Cell Sorting in Pillar Arrays based on Electrokinetics and Morphology

Deterministic Lateral Displacement (DLD) is a method capable of sorting cells based on size where mechanicalinteractions between a sufficiently large particle and obstacles in a microfludic pillar array force the particle tofollow a different trajectory than their smaller counterparts, resulting in continuous lateral separation. To extendthe capability of DLD, electrical interaction between particles and pillars can be employed to complement themechanical interaction, making electrical/dielectric properties additional parameters for sorting. Another idea isto exploit the morphologies of cells and as a concequence, their dynamical properties, to sort them in DLD. Thedevelopment of DLD cell sorting methods based on those two ideas has brought forth five papers appended to thisthesis: paper I, III, and V (combination of electrokinetics and DLD), and paper II and IV (exploiting morphologyin sorting by DLD).In the first topic, differences in electric properties or dielectric properties of particles and cells are employed toextend the capability of DLD. In Paper I, an AC electric field was applied across DLD devices having insulatingpillars to sort similar-sized polystyrene particles having different surface charge, viable from non-viable yeast cells,and viable from non-viable E. coli bacteria. In Paper III, the same method was utilised on open channel DLDdevices, showing unaltered effectiveness but offering the ability to flexibly change the distance between the electrodes.Also in the topic of combining electrokinetics and DLD, Paper V introduced a new type of DLD devicewhere the electrodes were defined locally on every pillar, making it easier to generate a high electric field strength.Besides electrical properties, morphology is another useful accompaniment to DLD. In Paper II, pathogenicStreptococcus pneumoniae bacteria were fractionated in DLD devices according to the difference in their morphology,viz. their chain length. It was also demonstrated, in paper IV, that an AC field can be used to rotatenon-spherical red blood cells and in turn, change their trajectory in a DLD device. This implies an opportunity tosort red blood cells from cells having different morphology, either spherical cells or parasites like trypanosomes

Graphene inspired sensing devices

Graphene’s exciting characteristics such as high mechanical strength, tuneable electrical prop- erties, high thermal conductivity, elasticity, large surface-to-volume ratio, make it unique and attractive for a plethora of applications including gas and liquid sensing. Adsorption, the phys- ical bonding of molecules on solid surfaces, has huge impact on the electronic properties of graphene. We use this to develop gas sensing devices with faster response time by suspending graphene over large area (cm^2) on silicon nanowire arrays (SiNWAs). These are fabricated by two-step metal-assisted chemical etching (MACE) and using a home-developed polymer-assisted graphene transfer (PAGT) process. The advantage of suspending graphene is the removal of diffusion-limited access to the adsorption sites at the interface between graphene and its support. By modifying the Langmuir adsorption model and fitting the experimental response curves, we find faster response times for both ammonia and acetone vapours. The use of suspended graphene improved the overall response, based on speed and amplitude of response, by up to 750% on average. This device could find applications in biomedical breath analysis for diseases such lung cancer, asthma, kidney failure and more. Taking advantage of the mechanical strength of graphene and using the developed PAGT process, we transfer it on commercial (CMOS) Ion-Sensitive Field-Effect Transistor (ISFET) arrays. The deposition of graphene on the top sensing layer reduces drift that results from the surface modification during exposure to electrolyte while improving the overall performance by up to about 10^13 % and indicates that the ISFET can operate with metallic sensing membrane and not only with insulating materials as confirmed by depositing Au on the gate surface. Post- processing of the ISFET top surface by reactive ion plasma etching, proved that the physical location of trapped charge lies within the device structure. The process improved its overall performance by about 105 %. The post-processing of the ISFET could be applied for sensor performance in any of its applications including pH sensing for DNA sequencing and glucose monitoring.Open Acces

Eurodisplay 2019

The collection includes abstracts of reports selected by the program by the conference committee