The purpose of the research was to determine whether PhET simulation labs or hands-on labs were more effective in helping students learn physics concepts. This measure was done by comparing quiz scores using recall, calculation, and transfer questions. Additionally, student perceptions of learning from both hands-on and simulation lab experiences were measured. Six labs were conducted with high school physics students on the topics of momentum, energy, circuits, angular momentum, pendulums, and friction. It was found that PhET simulation labs were as effective at creating student understanding, and sometimes more effective, as measured by quizzes given after the labs. Additionally, the survey data revealed that students were more engaged by hands-on lab experiences, and viewed the hands-on labs to be more effective than the simulation labs.

Lab-on-a-chip technology is a rapidly growing research area. Joining together several disciplines, such as physics, biology and several instances of nanotechnologies. The aim of this research is mainly to produce chips that can do the same types of measurements as large lab equipment and measurement systems, but at a fraction of the size and cost. In this work a multifunctional measuring device have been developed. It can measure optical absorbance and fluorescence while performing a range of potentiometric techniques; including chronoamperometry, linear- and cyclic voltammetry. From all these measurements it is possible to calculate particle concentrations in fluid samples. The aim is to bring simpler and cheaper point of care devices to the public. Without larger losses in accuracy and reliability of the medicinal test. To do this our device is intended to be used with lab-chip, which are capable of amplifying the signals while reducing the sample size. Lab-chips could be used in several areas but the ones being designed with this device are made for biomedical purposes, applying suitable nanostructures and reagents to measure the presence of biomarkers. With these techniques, medicinal diagnostics can be made a few minutes after samples have been collected from patients. Much quicker and more direct than sending the samples to a lab and waiting hours if not days for the results. The measuring device or lab-chip reader will use two different lab-chips in the future. One that is optimised for optical absorbance and the other for fluorescence. Both will work with electrochemical measurements, but at present only the absorbance chip have been available for testing and that without any signal enhancing techniques. Assessment of the reader's capabilities was made with solutions of gold nanoparticles, TMB (tetramethylbenzidine), iron dissolved in PBS (Phosphate-buffed saline) and with a film made of PPV (Poly para-phenylenevinylene). The first two were used to test absorbance; while the iron and PBS have been used to test electrochemical system; and the PPV was coated on a glass substrate and used to test fluorescence. During the optical absorption test, it was found that the reader can distinguish between different concentrations of the various solutions. The results are promising and further removal of signal drifts will improve signals considerably. Fluorescence can be induced and measured with the device. This part of the system is, however, untested in general and future work will show if it is sufficient. The iron solution was tested with three different methods. chronopotentiometry, linear sweep voltammetry and cyclic voltammetry. It was however found that our measurements were distorted in comparison with the expected voltammogram for iron in PBS. Additional peaks were found in the voltammogram and it is believed that these are a result of oxidation of the electrodes on the lab-chip.

Health-care delivery in developing countries has many challenges because they do not have enough resources for meeting the healthcare needs and they lack testing lab infras- tructures in communities. It has been proven that Point-Of-Care (POC) testing can be considered as one of the ways to resolve the crisis in healthcare delivery in these com- munities. The POC testing is a mission critical processes in which the patient conduct tests outside of laboratory environment and it needs a secure communication system of architecture support which the research refers as POCT system Almost every ten years there will be a new radio access technology (RAT) is released in the wireless communication system evolution which is primarily driven by the 3GPP standards organisation. It is challenging to develop a predictable communication sys- tem in an environment of frequent changes originated by the 3GPP and the wireless operators. The scalable and expandable network architecture is needed for cost-effective network management, deployment and operation of the POC devices. Security mecha- nisms are necessary to address the specific threats associated with POCT system. Se- curity mechanisms are necessary to address the specific threats associated with POCT system. The POCT system communication must provide secure storage and secure com- munication to maintain patient data privacy and security. The Federal Drug Admin- istration (FDA) reports the leading causes of defects and system failures in medical devices are caused by gaps between the requirements, implementation and testing. The research was conducted, and technical research contributions are made to resolve the issues and challenges related to the POCT system. A communication protocol implemented at the application level, independent of radio access technologies. A new methodology was created by combining Easy Approach to Requirement Specifications (EARS) methodology and Use Case Maps (UCM) model which is a new approach and it addresses the concerns raised by the FDA. Secure cloud architecture was created which is a new way of data storage and security algorithms models were designed to address the security threats in the POCT system. The security algorithms, secure cloud architecture and the communication protocol coexist together to provide Radio access technology Independent Secure and Expandable (RISE) POCT system. These are the contributions to new knowledge that came out of the research. The research was conducted with a team of experts who are the subject matter experts in the areas such as microfluidics, bio-medical, mechanical engineering and medicine.

This dissertation focuses on the applications of solid supported phospholipid membranes as mimics of the cellular membrane using lab-on-a-chip devices in order to study biochemical events such as ligand-receptor binding and the chemical mechanism for the preservation of the biomembrane. Supported lipid bilayers (SLBs) mimic the native membrane by presenting the important property of two-dimensional lateral fluidity of the individual lipid molecules within the membrane. This is the same property that allows for the reorganization of native membrane components and facilitates multivalent ligand-receptor interactions akin to immune response, cell signaling, pathogen attack and other biochemical processes. The study is divided into two main facets. The first deals with developing a novel lipopolymer supported membrane biochip consisting of Poly(ethylene glycol) (PEG)-lipopolymer incorporated membranes. The formation and characterization of the lipopolymer membranes was investigated in terms of the polymer size, concentration and molecular conformation. The lateral diffusion of the PEG-bilayers was similar to the control bilayers. The air-stability conferred to SLBs was determined to be more effective when the PEG polymer was at, or above, the onset of the mushroom-to-brush transition. The system is able to function even after dehydration for 24 hours. Ligandreceptor binding was analyzed as a function of PEG density. The PEG-lipopolymer acts as a size exclusion barrier for protein analytes in which the binding of streptavidin was unaffected whereas the binding of the much larger IgG and IgM were either partially or completely inhibited in the presence of PEG. The second area of this study presents a molecular mechanism for in vivo biopreservation by employing solid supported membranes as a model system. The molecular mechanism of how a variety of organisms are preserved during stresses such as anhydrobiosis or cryogenic conditions was investigated. We investigated the interaction of two disaccharides, trehalose and maltose with the SLBs. Trehalose was found to be the most effective in preserving the membrane, whereas maltose exhibited limited protection. Trehalose lowers the lipid phase transition temperature and spectroscopic evidence shows the intercalation of trehalose within the membrane provides the chemical and morphological stability under a stress environment.

To harness the wealth of success and computational power from the microelectronics industry, lab-on-a-chip (LOAC) applications should be fully integrated with silicon platforms. This works demonstrates a dielectrophoresis-based LOAC device built entirely on silicon using standard CMOS (complementary metal oxide semiconductor) processing techniques. The signal phases on multiple electrodes were controlled with only four electrical contacts, which connected to the device using three metal layers separated with interlayer dielectric. Indium tin oxide was deposited on a milled plastic lid to provide the conductivity and optical clarity necessary to electrically actuate the particles and observe them. The particles and medium were in the microfluidic chamber formed by using conductive glue to bond the plastic milled lid to the patterned silicon substrate. A correlation between the particle velocities and the electric field gradients was made using video microscopy and COMSOL Multiphysics ® simulations.

Lab‐On‐a‐Chip (LOC) or Micro Total Analysis System (μTAS) technology requires precise control of minute amounts of liquid. Moving liquids in small capillaries requires bulky expensive external pumps that defy the purpose of microfabrication. By integrating a micropump into the device, it allows the system to be transportable, reliable, energy efficient and inexpensive. Such a microsystem built on a chip has been designed to study separation by dielectrophoretic chromatography. Nanobeads were successfully separated and used separately to measure fluid velocity and study the electroosmosis effect. Cell or beads of different type can be trapped in this system. This system encompasses a solid‐state AC electroosmotic pump for the manipulation of liquid‐containing cells or molecules. AC Electroosmosis is the movement of induced charges over polarised electrodes created by a non‐uniform electric field. The charges undergo Coulomb forces and drag the fluid with their motion. This results in bulk flow over the electrodes. This micro pump is used in a LOC by fabricating the pump on two sides of a microfluidic channel. The transport of material from what can be an analyte to a cell is of critical interest. The described system in the second part of this thesis presents the advantage of having a defined number of droplets, each of which is a lab on chip. The paradigm is the droplet and therefore the vessel that carries the information. Surfaces are then the place of interaction with the vessel which carries the second aspect of this thesis. Several approaches have been investigated, in particular by enclosing the droplet between two slides in order to increase the change of contact angle under the presence of polarised electrodes. This system is known as EWOD (ElectroWetting On Dielectric). It follows the approach of modified Lippmann laws and the modification of the apparent contact angle and therefore the motion of the droplet. The lid is somewhat a problem and the possibility of using liquid dielectrophoresis to create a multitude of droplets of calibrated volume is an advantage, as it is harder to create fixed‐volume droplets with an open geometry by EWOD due to contact angle hysteresis.

To harness the wealth of success and computational power from the microelectronics industry, lab-on-a-chip (LOAC) applications should be fully integrated with silicon platforms. This works demonstrates a dielectrophoresis-based LOAC device built entirely on silicon using standard CMOS (complementary metal oxide semiconductor) processing techniques. The signal phases on multiple electrodes were controlled with only four electrical contacts, which connected to the device using three metal layers separated with interlayer dielectric. Indium tin oxide was deposited on a milled plastic lid to provide the conductivity and optical clarity necessary to electrically actuate the particles and observe them. The particles and medium were in the microfluidic chamber formed by using conductive glue to bond the plastic milled lid to the patterned silicon substrate. A correlation between the particle velocities and the electric field gradients was made using video microscopy and COMSOL Multiphysics ® simulations.

Zugl.: Dortmund, Techn. Univ., Diss., 2009

Number pattern generalisation is often regarded a difficult topic for students to learn. To explore this perception, the present study undertakes an empirical investigation with the main aim of providing a comprehensive description of how 14-year-old secondary school students in Singapore generalise figural patterns and justify their generalisations when varying the formats of pattern display and the types of function. Comprising two interrelated parts, the study first examines 515 students’ strategies and justifications and probes systematically the influence of the formats of pattern display and the types of function on their generalisations through a specially developed paper-and-pencil test. The other part, through a specially designed questionnaire, looks at their beliefs about which strategy would best help them to derive the rule for predicting any term of a figural pattern as well as their ability to construct the rule using their choice of strategy. The first part uses an independent-measures research design to examine whether different formats of pattern display have any effect on students’ rule construction and a repeatedmeasures research design to determine whether their rule construction is influenced by the different types of function. In the second part, a survey study is employed with all students asked to identify their choice of best-help generalising strategy. This is then followed by interviews with 16 of the 515 students to probe whether they are able to derive a correct functional rule using their chosen strategy. This study complements many previous studies mainly undertaken in the west in that its findings indicate that the more academic students are competent in developing a functional rule for linear patterns but falters when working with quadratic patterns. There is a widespread failure of the less academic students in both linear and quadratic patterns, confirming the oft-regarded view that expressing generality is elusive. Successful students perceive the patterns in several ways and generate wide-ranging functional rules, predominantly symbolic, to describe them. They employ a variety of generalising strategies, especially the figural type, and some of which are new in the literature. Both the test and the survey confirm that the figural strategy involving the breaking up of the whole configurations into non-overlapping parts is their clear favourite. For rule justification, verifying it using the numerical cues and drawing diagrams to explain its development are their favourite approaches. Task features such as the format of pattern display and the type of functions do contribute to student difficulties in generalisation. Based on these findings, some useful teaching strategies for teachers and teacher educators are then suggested to help them improve their teaching of pattern generalisation. The findings also point the direction for future research studies on pattern generalisation by suggesting some recommendations for researchers.

This study investigates students’ construction of the English for Specific Purposes (ESP) classroom, that is, ESP teaching and learning, and uses the Participatory Design (PD) approach to the design of educational technology as a means to improve and refine our understanding of their construction of the classroom. The study was carried out with Brazilian university students on a Computer Science course. Following general guidelines of the PD approach, the researcher invited an ESP teacher, a number of students, and a Software Engineer to collaboratively design a Web Portal to support ESP teaching and learning. The research questions were: (i) how do students construct the ESP classroom? and (ii) to what extent does students´ involvement in the process of designing educational technology for ESP bring to light different elements of this construction? Data were collected in two phases. Firstly, an initial interview was carried out and then records of students´ participation in the workshops, their entries in an online diary and a final interview were collected. A bottom up approach was adopted to categorisation of the beliefs constituting the students’ construction of the classroom, and the analytical framework outlined by Benson and Lor (1999) was used to help to interpret and group these classifications. The final model of the students’ construction identified four groups of beliefs, clustered around the ideas of accumulation, communication, autonomy and unease with what the ESP course offered. The use of Participative Design as a method to facilitate the collection of data about the students’ construction of the classroom was found to be effective in enabling the research to move from an description based on students’ de-contextualised descriptions of the classroom in the initial interviews, to a more articulated and detailed level of description that emerged from involvement with the design task.