MacDonald Lab

We are currently developing and prototyping Stirling engines. Stirling engines can operate at much higher efficiencies than internal combustion engines, and they can be powered by a number of different heat sources, since the heat is provided externally. This means that Stirling engines provide a reliable way to harness renewable sources like solar thermal energy, waste heat, and biomass, since the engines can be powered by multiple heat sources and the intermittency of the sources can be overcome.

We developed and patented our TrueCycle technology so that our Stirling engines can follow the actual Stirling cycle and have much higher efficiencies than past "Stirling engines." We are currently using modelling and experimental testing to achieve the highest efficiencies possible, which will allow us to produce more power and use lower temperature heat sources.

We are also commercializing this technology so we can have a large impact by reducing carbon emissions and combating climate change. The startup company is called Ekstera Inc. and we are currently working on demonstration projects for our Stirling engines with industrial partners.

We developed a number of tests using paper-based and textile-based microfluidic platforms, and devised new methods for fabrication and flow characteristics in capillary-driven devices. Paper-based devices have the advantages of being affordable, equipment-free, disposable, rapid, safe, and easy-to-use. We developed a paper-based test to detect arsenic contamination in the groundwater in Bangladesh, and verified the tests with water samples collected from hand tubewells in Bangladesh. Our research into paper-based and textile-based platforms encompassed both modelling and experiments about the capillary-driven flow behaviour, fabrication techniques, incorporation of reactants and control of reaction zones, field testing, and impact of the technology.

Our research aimed to improve evaporative cooling technology by enhancing evaporation rates of sessile droplets through manipulation of interfacial properties. We investigated evaporation rate enhancements both experimentally and through modelling, and developed and designed improved evaporative cooling systems with high energy efficiency. Marangoni convection is an example of an interfacial phenomenon that has been shown to enhance evaporation rates and in certain cases is responsible for some of the energy transport to the interface of evaporating sessile droplets. Evaporative cooling systems can play a crucial role in meeting the rising demand for thermal management, particularly in fields requiring high heat removal density, like microelectronics.

We developed a scalable, out-of-plane desalination approach using a phenomenon at the confluence of micro- and nano-fluidics, known as "ion concentration polarization."

The devices were capable of producing fresh water from sea water in an energy efficient and scalable manner, which is particularly important for people in developing countries (where electricity is expensive and/or scarce) to have access to fresh water. The out-of-plane design enables multiplexing in three dimensions, providing the functional density required for practical application.

We developed a low cost, simple and integrated device for medical diagnostics in low-resource settings called the lab-in-a-pen. Finger pricking, and sample collection and processing, were integrated with commercially available paper-based assays in a pen format. This approach ensures safety (i.e. biological sample and sharps containment) and can be used by untrained end users across multiple settings.

A partnership with the National Hospital for Tropical Disease in Hanoi, Vietnam enabled in-field testing of the prototype devices with patients for Hepatitis B surface antigen (HBsAg) and Hepatitis B 'e' antigen (HBeAg).

We investigated the stability of evaporating liquid sheets, conical funnels, and sessile droplets. Linear stability analyses were used to generate stability parameters with insulating and conducting substrates to predict the onset of Marangoni convection. Parametric analyses were completed for the stability parameters to determine the influence of the input parameters on the onset criteria.

The stability parameters can be used to predict the onset to Marangoni convection for physical systems, and are particularly useful since they contain no arbitrary fitting parameters. Applications for these predictions include designing energy efficient thermal management for microelectronics devices, manipulating pattern formation for coatings, and self-assembly using evaporating sessile droplets.

We investigated external heat transfer enhancements on metal hydride hydrogen storage tanks using a numerical model that we developed. We examined thermal coupling with energy converters (fuel cell pictured at right) using a numerical model that was capable of dynamic simulations, which could model cyclical loading and represent accurate operating conditions.

An experimental investigation was completed using commercially available and proprietary metal hydride alloys from an industrial partner to validate the model. A parametric study was also undertaken to understand the relative importance of the design parameters and facilitate design of metal hydride hydrogen storage systems.