For our senior design project in Bioengineering, my group and I built a prototype of a medical device. The device was a transcutaneous ultrasound generator, and produced ultrasound waves necessary to stimulate the vagus nerve. Studies have shown that specific stimulation of this nerve can treat epilepsy and treatment-resistant depression.
We communicated with our client to understand their needs and requirements, studied existing devices to determine their strengths and weaknesses, and conducted research to determine what kind of ultrasound wave would effectively stimulate the vagus nerve. Our final product was handheld, portable, easy to use, and reliably produced an ultrasound wave.
For our senior design project in Electrical Engineering, my partner and I designed and built modular printed circuit boards that run simulations of Conway's Game of Life. To set the initial conditions of a simulation, one can toggle the LEDs on and off by shining a laser pointer on them. The boards can be connected to run larger simulations and can be connected or disconnected seamlessly while the simulation is running.
Each board had an 8x8 array of LEDs. To detect laser pointer input, we reverse biased the LEDs and used them as photodiodes. Since our LEDs were green, we used a violet laser pointer (emitting light at a wavelength of 405 nm) to ensure the photons emitted had higher energies than the bandgap of the LED semiconductor.
The boards are powered by 9 volt batteries. I designed and built a circuit that pulls an input high on the microcontroller when the battery voltage is low, so the user can be alerted and change the battery.
The second op-amp acts as a comparator and receives two voltages: The battery voltage minus 1.75 V (at the inverting input) and the low batery voltage of 7 V minus 1.75 V (at the non-inverting input). The second voltage is supplied by the first op-amp, which amplifies a constant 1.75 V by a constant gain of 3. This produces a constant 5.25 V, which equals the low battery voltage minus 1.75 V. Thus, when the voltage at the inverting input of the comparator falls below the voltage at the non-inverting input, the battery is low and the output of the comparator will be high. A voltage divider at this output ensures that the voltage received by the microcontroller will be a TTL logic high or low as desired.
Our project worked reliably as planned and we won the Design Award, for the project that best exemplifies the engineering design process! To see the printed circuit board layout, or download its EAGLE file, check out this page.
I own a Vox AD30VT amplifier which has a variety of gain, modelling, and effects settings. Vox also sells a foot switch that allows you to toggle between two presets and turn your effects on and off. They typically sell for at least $30, but are actually quite simple to make on your own.
Using this schematic from the service manual I understood how the foot switch interacted with the amplifier and how to build a device that did the same thing. Here is the first one I built, out of an old Windsor radio:
It works perfectly and the radio enclosure gives it a unique look I really like. After realizing that these were simple to make and normally cost customers much more money than I spent to build one, I wanted to make them for other people too. Here's one I built and sold on eBay:
The buyer left feedback saying, "Fast shipping product worked great very happy with purchase!"
For a bioreactor course at my university taught by Dr. Jenny Amos, I designed and built a skeletal muscle bioreactor that facilitates the differentiation of C2C12 myoblasts into myotubes (skeletal muscle cells). Methods to encourage the differentiation of myoblasts into myotubes include adding horse serum to the media they grow in, stretching the surfaces they grow on, and stimulating them electrically. For this experiment, the effects of stretching and electrically stimulating the cells were assessed.
After reading literature (see this article and this article), I determined that an electrical stimulation pattern and flexible cell culture dishes from Flexcell International, both pictured above, ought to be used. The vacuum tension system that Flexcell produces was too expensive for an undergraduate lab budget, so I designed a system that stretched the cells using a servo instead. An Arduino microcontroller was used to control the servo and stimulate the cells electrically, and was programmed with this code.
With the help of a few other students, I worked on this project and presented it at the University of Illinois Engineering Open House in 2012 and 2013. The first year, all the cells died except those in the control group, that received no stimulation. It wasn't clear why, and the results were disappointing. Next year, the results were significantly better. The cells were stained green for actin, a protein present regardless of differentiation, and red for troponin, a protein that grows in myotubes but not myoblasts.
As can be observed from the images above, physical and electrical stimulation decreased the number of living cells (reducing green fluorescence) but increased differentiation (producing red flourescence). This provides an interesting possible explanation for our results over the two years: The first year, we overstimulated our cells, killing them all except the control group, but the second year, we were pressed for time and stimulated our cells less, giving us better results purely by accident.
Ironically, it was during the first year that our project won first place in the "Dream Design Discover" category, but seeing our project work correctly the second year and understanding the reason was the award that meant the most.