Academic work

Publications & further info: Researchgate.net/profile/oliver_barham

 

PhD Research (2013 - 2017)

Microfabricated Piezoelectric Voltage Transformers

From 2013-2017 I was a graduate student at the University of Maryland, College Park, taking classes in electrical and mechanical engineering. I worked for Mechanical Engineering professor Don DeVoe in the MEMS and Microfluidics Laboratory (mml.umd.edu), studying piezoelectric voltage transformers. My dissertation can be found here:

https://drum.lib.umd.edu/handle/1903/19842

A voltage transformer transforms electrical energy from a given input voltage into a different output voltage, in order to meet different system voltage needs. For example, step-down voltage transformers are used by electric utilities to change thousands of volts riding on high voltage power transmission and distribution lines into one hundred and twenty volts used in residential homes. These common types of transformers are manufactured using several separate coils of metal wire which exchange energy between themselves using electromagnetic fields. My work focused on using piezoelectric materials to manufacture micro-scale voltage transformers that work on a different principle, and rely solely on mechanical energy transfer, instead of electro-magnetic. When electrical energy is applied to these devices they mechanically vibrate, transferring energy in this way from one part of the device to another, and in doing so create a different voltage than the one originally applied. In comparison to electro-magnetic transformers, piezoelectric transformers can be made at smaller scales, where winding coils of wire would be difficult, and do not emit electro-magnetic fields when in operation, thereby avoiding potential electro-magnetic interference with nearby electrical devices. My work was motivated by small applications such as micro-robotics and micro-electro-mechancial systems.

MS Research (2005-2007)

Mechanics of Microneedles

Above you can see a scanning electron microscope image of a female mosquito, equipped by nature to draw blood through the use of a long, slender, flexible, needle-like tube called a fascicle. It is so small in diameter (roughly 0.000030 meters) that humans cannot feel it when it is inserted through the skin. You may have noticed a mosquito on your skin that is busy drawing blood, although you did not feel her prick you, and swatted her away, only to see a raised bump appear later - caused by the mosquito's saliva, which contains a blood-thinning agent.  Both males and females feed primarily on plant nectars; females use nutrients found in human blood to help in developing eggs.

If needles on this scale could be designed and manufactured artificially, painful blood drawing and drug delivery could be a thing of the past. Diabetics, young infants and anyone that dislikes needles would no longer feel the pain now associated with them. Can we presently manufacture needles on this scale? Yes, needles have been produced using various chemical processes, but unfortunately generating the right combination of mechanical properties has been difficult. Penetrating the various layers of the skin without exceeding these properties has been challenging. If a needle were to break off inside the skin, and pieces could travel through the circulatory system, it could have disastrous consequences for the patient, so this must be avoided at all cost.

My work looked at the combination of roles played by the fascicle's outer sheath (the labium) and the force exerted by the mosquito's head tangent to the bending fascicle (the non-conservative "Beck" load). Mathematical equations representing these components were analyzed using a computer, and the final outcome was a determination that the labium support has a much greater affect on critical buckling load (how much force you can apply to the needle before it breaks or bends so that it cannot be inserted into the skin) compared to the Beck load. So, for example, biomedical engineers working on microneedle systems may want to concentrate on supporting them radially while they attempt to penetrate the skin's tough outermost layer, which is relatively more important than the precise angle used when applying force to the needle.

 

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