| Around the world, people are faced with the challenge of dealing with cancer every day. The number of new cases of cancer rises every year. In North America alone there were 1.6 million new cases reported in 2002. Many of these cases are treatable, however, there are many types of cancers which are classified as drug resistant tumours. These entities do not respond to chemotherapy drugs as their cell membranes have an innate ability to exclude the drugs. Currently there are no viable treatments for drug resistant tumours which can not be removed surgically. Although this is a dire situation, there has been significant research performed over the last 10 years on the topic of altering cell membrane permeability which could lead to a treatment. By increasing the permeability of the tumour cells using mechanical forces induced by oscillating gas microbubbles excited by ultrasound, it is believed that tumour treatment efficacy can be increased greatly. Artenga Inc. of Ottawa, Ontario in Canada is developing a device which can generate and deliver gas microbubbles and chemotherapy drugs into a tumour in order to treat drug resistant tumours. Their TBI (Transient Bubble Infusion) device will consist of a bubble generator and drug dispensing system. The work in this thesis is a theoretical and experimental investigation into bubble generation at a micro-scale orifice for use in the Artenga TBI. Three experimental scenarios are investigated: Constant gas flow bubble generation in a static liquid, constant gas pressure bubble generation in a static liquid and constant gas pressure bubble generation in a liquid cross flow. The first scenario allows investigation and confirmation of the effects of the previous generated bubble on the next bubble, called the bubble wake effect. The second and third scenarios demonstrate that constant pressure bubble generation at an orifice would not meet the requirements of the TBI device however the technique is useful for researchers working with low concentrations of bubbles. In addition to the experimental work, a theoretical force balance model is developed to predict the size of a generated bubble at a microscale orifice under constant applied gas pressure in a static liquid. By taking the compressibility of the gas, dynamic surface tension of the liquid, bubble-orifice contact angle and the bubble wake effect into account, the force balance model successfully predicts the generated bubble size. |
