P-LA! and DF-LA! (INNOVATION)^[a]

Function

Plate-Dish-Flask Light Apparatus (PDF-LA!) is a suite of three fully programmable devices compatible with standard laboratory equipment. It was used to characterize our optogenetic circuit in 12-well plates, petri dishes, and Erlenmeyer flasks.^[b]

Design

We designed PDF-LA! to help us characterize the behaviour of EL222. A research fellow sharing our lab, Dr TEH Ai Ying (Figure 1), was also interested in using our custom optogenetic tools, and so she served as our main source of user feedback throughout PDF-LA!’s design process.

P-LA!

The first design was a device for the 12-well plate, P-LA!. We designed P-LA! to improve on another design which had been loaned to us by a different university (Figure 2), and hence gain experience of creating custom tools for optogenetics research.

P-LA! is better than the previous design because it can accommodate 12-well plates from different manufacturers, whereas the other design could only fit a specific 12-well plate model (Figure 2). P-LA! also uses significantly less material. Fun fact: despite its name, P-LA! was printed with ABS filament rather than PLA filament! All our 3D-printed designs use ABS filament as it was made readily available to us by our university, and its material properties were deemed sufficient for our purposes.

After optimizing our device for the 12-well plate, it was time to scale up and create devices for petri dishes and Erlenmeyer flasks. These two items of standard laboratory equipment were chosen based on feedback from research fellows in NUS. To provide users a more integrated solution, we produced a single device which can be used for both, DF-LA!.

As such a device had not been designed previously, there was no existing structure to improve or draw inspiration from, and our team started from scratch. This resulted in many design iterations (Figure 13).

The first iteration is for a single petri dish, which can be illuminated from top and bottom. Users wanted a system with the additional option to test two petri dishes at once, and the second iteration was conceived.

The second iteration was designed such that the components to illuminate a single petri dish from the bottom could be stacked with another set of the same components to create a structure that could expose the petri dish to light from the top and bottom. This symmetry is advantageous as the functionality of a single unit doubles, and was therefore retained and developed in subsequent design iterations.

After that, we attempted to design a separate device for the Erlenmeyer flask, but realized that it would be much simpler and more elegant to adapt the second iteration to also accommodate the flask. The third iteration thus has an extra ring in between the devices for the petri dish. This acts as a holder for the flask. Also, the “teeth and slots” feature used to join the components together has moved from the center of the walls of the cylinder to the outer edge of the cylinder. We intended to shake the flask, and were thus concerned that the walls of the slot and the teeth would be too thin and might break due to shear stresses. We thus modified this feature for the third iteration.

Major changes from the third iteration to the fourth iteration are the increase in the height of the flask adapter so that the flask could also be illuminated from both top and bottom, the increase in the number of LEDs available to illuminate the flask or dish, and modifying the shape of the electronics container so that the whole structure could be cylindrical. The reason for the last change was fivefold - firstly, to reduce the material expended during 3D-printing, secondly, so the device would occupy a smaller area, thirdly, for the user’s comfort during transport as the inconsistency in shape made the structure unwieldy to carry, fourthly, to make the design aesthetically pleasing, and last but definitely not least, the design now becomes infinitely more modular as users can now continuously stack combinations of D-LA!, the petri dish module, and F-LA!, the erlenmeyer flask module, into a single column. As the components are lightweight, structural failure is not a concern, and the number of units a user can stack is only limited by the microcontroller. Many petri dishes and flasks can be illuminated simultaneously while still occupying the same area as a single testing unit. For more on the increased functionalities of our final iteration of DF-LA!, please visit our Hardware page.

Users reported satisfaction with the final design iteration. Please visit our Hardware page for more on how we conducted user testing and learned from user feedback.

[a] To include: feel free to doodle on your PDF-LA! as we ourselves have done. May it liven up many a dreary lab session.

[b] How was it used in the context of iGEM, do the same for Light Wait. This differentiates it from earlier, when we talked about it in the context of synthetic biology research in general.