CT Scan

To get a closer look at the internal structure of our hollow fiber reactor and to monitor the durability of the fibers after heavy filtration we got a Computed Tomography (CT) scan of the reactor with the help of Cornell's Biotechnology Resource Center Imaging Center. We are very concerned with how the fiber material holds up to use as we don't want the filter to be compromised and for our cells to escape into the environment. This technique could be used to determine the life-span and suggested replacement times of such systems.

Material Design

The box has been tested to last for over 5 months in our project for 2012. Since it is meant to be used outside in the field, the box must be durable and water proof in order to filter the polluted water and safeguard the electronics from the environment. The box is also self-sustaining in a sense that a solar panel is used to provide electricity for the electronics and that it can endure the environment as it may be placed by a river to sequester some of the heavy metals from the river.

Flow Rate Testing

In order to determine our requirements for the pump, we tested the flow rate through a setup with the prefilter and fiber reactor. Since the fiber reactor membranes are extremely delicate, we had to make sure our pump could overcome the system’s high resistance without causing any leaks. Initially, this was quite difficult, since we had to prime the system with water for the pump to work at all. The prefilter does not outlet any water until it is completely full. We were able to solve this by connecting the inlet to a separate water source and using hydrostatic head to carefully fill each component. We then matched the fiber reactor’s maximum pressure rating to the pump’s outlet pressure based on the current from the power supply.

Luria Broth Testing

One factor in the longevity of living cells in our fiber reactor system is the retention time of growth media in the outer chamber. To test this retention time, a test was conducted to see how long it took for LB to completely leave the fiber reactor. Tonic water fluoresces under UV light because it contains quinine, so solutions of LB and tonic water at varying ratios were run through the fiber reactor. The volume and amount of dilution of the mixture leaving the fiber reactor was measured via the amount of fluorescence. Overall, it was determined that LB does not remain in the fiber reactor for a long enough time to support growth. To support long-term growth, we would have to incorporate a separate media cycling system into the reactor. However, this reactor system uses very slowly growing cells that does not require media for growth, so this is not a huge concern for our project.

The picture on the right, from left to right, is 50/50 LB-tonic water mixture inserted into the reactor, the output from the fiber reactor, the mixture left in the fiber reactor, and water.