Team:UCLouvain/Badge
The design of the badge has been a significant part of our work. It must be small, practical and bio-secure, preventing our bacteria from escaping into the environment. As our badge is specifically made to be used outside the lab, the biosecurity aspect needed careful attention. To respect these specifications, we decided to set it up as an assembly of three separate pieces, all of which can be 3D printed. Some parts are also safely reusable, so you don’t have to replace the entire badge when it is used.
The first one is the support, that can be attached to a bracelet by simply pulling it through the gaps on both edges. This part will never get in contact with the bacteria and is thus reusable. The middle part of the support contains a hole, allowing the second part of the badge to come in and to be secured, thanks to the groove on the side and on the bottom.
The second part is the heart of our system, we call it the capsule. It’s the piece that holds the medium containing our UV sensitives bacteria. Therefore, it is completely sealed, except for a small hole left on the side which allows us to fill it with medium and bacteria. This hole will also be used to ensure the biosafety of our badge, in cooperation with the last part. Regarding the top of the capsule, it is covered with a transparent polymer, that lets both visible and UV light pass through. There are also two smalls teeth on the bottom which fit into the support grooves to secure the capsule in place. You can finally find a small bump on top of the hole which will be used to secure this piece into the support using the final part.
Last but not least, the next part is called the safety ring. It will act as one of our biosecurity features. It’s a hollow cylinder that contains bleach, connected to the outside only by a small hole on the inside. Similarly to the hole in the capsule, this one serves as an opening to fill the ring and as the second cooperating part regarding the biosafety mechanism. You can also find a little bump on top of the ring, which is hanging inside. This ring is placed around the capsule, which is already inside the support. The ring needs to be able to turn freely around the capsule, only limited by the small bumps.
A seal is needed in-between the last two parts to ensure that there are no leaks. Once the three parts are assembled and filled with their respective liquids, the badge is finished and ready to be used.
In order to secure the capsule into the support, you need to put the capsule into the support first, by matching the teeth with the grooves. Then you add the safety ring around the capsule, making sure that the holes are not facing each other. Finally, you turn the safety ring clock wise. When the bumps on the capsule and on the ring come into contact, continuing turning will force the capsule to turn with the ring. It will be secured inside the support, thanks to the groove at the bottom. The badge is now assembled and ready to be used as a UV sensor.
Once the capsule has been used, it needs replacing. To do so, simply turn the ring anticlockwise. Once the small bumps are in contact, keep turning. The small capsule will turn too, enabling it to leave the support with the ring. When the small bumps get in touch, both hole in the capsule and in the safety ring will perfectly match. This means that the solution of each compartment will be mixed together. The bleach will kill all the bacteria, leaving nothing but dead cell fragments and protein aggregate. Using this mechanism, we ensure that every time a capsule is replaced, the bacteria inside the old capsule are killed. The capsule can then be trashed safely or recovered to replenish it with bacteria.
Our prototype was printed using a MakerBot Replicator 2X Experimental 3D Printer and with polylactic acid (PLA) as a polymer. The top of the capsule was not printed due to some technical limitation. Nevertheless, poly(methyl methacrylate) (PMMA) could be used as it allows light transmittance in the visible range and at our desired wavelength (365 nm)[1].
[1]Ahmed, R. M. 2009. “Optical Study on Poly(methyl methacrylate)/Poly(vinyl Acetate) Blends.” Research article. International Journal of Photoenergy. 2009
