Proof of Concept

In order to fulfill the proof of concept gold medal criteria we tested our devices (BBa_K1895000, BBa_K1895006, BBa_K1895004) in components compatible with our modular breadboard.

The functional proof of concept of our project was demonstrated by integrating three of our BioBricks in the following devices:

  1. Microbial Fuel Cell
  2. Heat Induced ‘Light Bulb’

Microbial Fuel Cell

We designed a miniature fuel cell part compatible with the modular design of our breadboard circuit system which we had spent the summer designing. Our design procedure can be seen here.


Figure 1. The construction of our miniature microbial fuel cell component using a 3D printed mold and PDMS gel.

This miniature device allowed us to test our construct BBa_K1895004 under the real world conditions in which it would be used. The miniature device was made using a 3D printed mold made of Poly Lactic Acid (PLA) designed on TinkerCad and cast using Poly Dimethyl Siloxane (PDMS) gel. This device can be attached to our modular breadboard kit using magnets, which will also allow electrical flow.

In order to test this miniature device, the protocol previously used to test our constructs in the Reading microbial fuel cell, had to be edited. Our new protocol was appropriately scaled down and the same buffers were used.The full version can be seen here.

We successfully measured a voltage output from the miniature fuel cell containing E. coli with our BioBrick device (BBa_K1895004) inserted. The results can be seen below. You can also view all results concerning this part here.


Figure 2. Output of our microfluidic microbial fuel cell (mean±SE, mV) using the BBa_K1895004 construct undergoing porin expression. Solutions were made up as per the larger fuel cell, thoroughly mixed and injected by syringe to fill each chamber following insertion of the cation exchange membrane. Voltages were measured every 3 minutes via digital voltmeter and the experiment stopped after 60 minutes. For more information on how we designed the miniature fuel cell, please see our hardware design page

Heat Induced ‘Light Bulb’

Similarly to the battery constructs, we planned to test our constructs (BBa_K1895000 and BBa_K1895006) using a microfluidics style device that will be integrated into our modular breadboard using custom built components.


Figure 3. The modular light bulb component compatible with our breadboard.

We have previously shown that both of our ‘light bulb’ constructs can be induced with a temperature of 37°C but this induction is intensified with an even higher temperature of 42°C. In order to prove our concept we first started by attempting to create a heating effect on LB broth within our microfluidics chamber using an electrical current. We timed how long it took to cause a 15°C change in the LB media, enough to induce the promoters in both of our ‘light bulb’ constructs. We tested times at varying currents from 8 to 20 mA; the times were relatively short with the heating taking less than 60s on many occasions.


Figure 4. Time taken in seconds to cause a 15°C increase in temperature of 250μl of LB broth in our microfluidic light bulb component with varying currents(mA).

This result along with the previous data collected regarding the effect of temperature on E. coli containing our construct (seen here) demonstrates our proof of concept nicely.