Development of an integrated complex 3D fluidic device assembled from fully characterised functional blocks: Michaelis-Menten enzyme kinetics analysis as a case study

The work presented in this thesis demonstrates a new approach to the design of integrated uidic devices. Most `lab-on-a-chip' are in fact `chips-in-a-lab'. The equipment used to operate them, such as microscopes and syringe pumps, is bulky, expensive and the portability is non-existent. Fluidic devices operate on multiple domains, such a fludics, pneumatics, sensing, control, etc. By integrating the domains to a single device, cost can be reduced and portability increased. A new manufacturing process was developed to allow for the integration of multiple domains. The vast majority of fluidic devices are two-dimensional, made via soft lithography, which limits the complexity and integration of other components. Three- dimensional fluidic devices can be used to create complex intricate networks and can include sensors, actuators and optics. A negative mould was 3D printed in Acrylonitrile Butadiene Styrene (ABS), encased in Polydimethylsiloxane (PDMS) before being placed in an acetone bath. Because of the swelling properties of ABS in solvents, Acetone could reach the embedded ABS. ABS was liquefied in the presence of acetone, making it possible to be flushed from the PDMS, leaving a void. Following the development of the manufacturing process, functional fluidic blocks were developed to create more complex devices based on usage. Each block was designed to perform a given task, including a photometric sensor, a proportional valve, a turbulent flow mixer, and storage wells. Using the blocks that were developed, a device designed to perform Michaelis-Menten enzyme kinetics analysis was demonstrated. The device was operated by a combination of a custom PCB and a Matlab GUI, thus creating an integrated system. Enzyme kinetics were analysed by determining the initial reaction rate of the enzyme-catalysed reactions for various concentration of its substrate. In order to determine reaction rates, it is common to monitor the opacity of the reaction product over time. This is often achieved by using a substrate (or a substrate analogue) which produces a product with a unique optical absorbance, thus the opacity of the product can be monitored by absorption spectroscopy. The experiment was repeated for multiple concentrations before the kinetics were extrapolated. The device created can perform the same task, as well as automating the mixing of any concentration necessary for the kinetic analysis, at fraction of the cost of commercial equipment

Test Structures for Developing Packaging for Implantable Sensors

With their capacity for real time monitoring and spatial mapping, implantable sensors are becoming an increasingly important aspect of next generation precision healthcare. Microfabricated sensor systems are a popular choice, owing to their capacity for miniaturisation, repeatable mass manufacture, and numerous pre-existing sensor archetypes. Despite the drive for development, packaging these sensors for the environment within the body, as well as the implantation process itself, presents a significant challenge. This paper presents microelectronic test structures, which can be used to assess, compare, and optimise implantable packaging solutions in a standardised manner. The proposed structures are used to investigate: (i) the capacity of the material to be patterned, (ii) the permeability of the insulation material, (iii) adhesion of the encapsulant to the die, and (iv) the physical robustness of the package to implantation through a needle. They are used to characterise an example packaging strategy, using biocompatible epoxy-resin. In addition, a method of optimising the packaging performance using the test structures is presented

Leidenfrost heat engine: Sustained rotation of levitating rotors on turbine-inspired substrates

The prospect of thermal energy harvesting in extreme environments, such as in space or at microscales, offers unique opportunities and challenges for the development of alternate energy conversion technologies. At microscales mechanical friction presents a challenge in the form of energy losses and wear, while presence of high temperature differences and locally available resources inspire the development of new types of heat engines for space and planetary exploration. Recently, levitation using thin-film boiling, via the Leidenfrost effect, has been explored to convert thermal energy to mechanical motion, establishing the basis for novel reduced-friction heat engines. In the Leidenfrost effect, instantaneous thin-film boiling occurs between a droplet and a heated surface, thereby levitating the droplet on its own vapor. This droplet state provides virtually frictionless motion and self-propulsion, whose direction can be designed into the system by asymmetrically texturing the substrate. However, sustaining such thermal to mechanical energy conversion is challenging because the Leidenfrost transition temperature for water on a smooth metal surface is 220°C and, despite the low thermal conductivity of the vapor layer, the droplet continuously evaporates. Further challenges include effective transfer of thermal energy into rotational, rather than linear motion, and driving solid components and not simply droplets. Here we present a Leidenfrost rotor, where a solid component is coupled to a rotating liquid volume using surface tension and levitated in continuous operation over a turbine-inspired substrate. We address two key challenges: we show how the liquid can be replenished to achieve the continuous operation of the device; and we show how a superhydrophobic coating to the substrate can broaden the temperature range of operation and the stability of the rotor. Because the liquid acts as a working substance by extracting heat from the substrate to produce useful work in the form of rotation of the coupled solid component, our results demonstrate that a Leidenfrost engine operating in a closed thermodynamic cycle is possible

Limpet II: A Modular, Untethered Soft Robot

The ability to navigate complex unstructured environments and carry out inspection tasks requires robots to be capable of climbing inclined surfaces and to be equipped with a sensor payload. These features are desirable for robots that are used to inspect and monitor offshore energy platforms. Existing climbing robots mostly use rigid actuators, and robots that use soft actuators are not fully untethered yet. Another major problem with current climbing robots is that they are not built in a modular fashion, which makes it harder to adapt the system to new tasks, to repair the system, and to replace and reconfigure modules. This work presents a 450 g and a 250 × 250 × 140 mm modular, untethered hybrid hard/soft robot—Limpet II. The Limpet II uses a hybrid electromagnetic module as its core module to allow adhesion and locomotion capabilities. The adhesion capability is based on negative pressure adhesion utilizing suction cups. The locomotion capability is based on slip-stick locomotion. The Limpet II also has a sensor payload with nine different sensing modalities, which can be used to inspect and monitor offshore structures and the conditions surrounding them. Since the Limpet II is designed as a modular system, the modules can be reconfigured to achieve multiple tasks. To demonstrate its potential for inspection of offshore platforms, we show that the Limpet II is capable of responding to different sensory inputs, repositioning itself within its environment, adhering to structures made of different materials, and climbing inclined surfaces

A Low Cost Patternable Packaging Technology for Biosensors

This paper demonstrates a simple and low cost technology to reliably and accurately package integrated chips. Microchannels and cavities of minimum feature size of 500 μm can be reliably reproduced. In addition, the curing depth in relation to the exposure time was investigated. A simple microfluidic device, consisting of a 500 μm channel and 2 mm ports, was manufactured to demonstrate the possibilities of this technology. Extensive electrochemical experiments showed that the packaging material is a good insulator and leaves no residue on the chip