Within the STEMulate Learning workshops, several events have been focused on SOLID Learning principles to test and share the potential for 3D Printed materials and tools. The purpose of the SOLID Learning effort has been to develop 3D Printable resources for educators and students to include in their classrooms. The latest workshop involved a 3D Printed centrifuge design that allows a common rotary tool to separate samples for later study.
This design is termed a “DremelFuge” (Thing #1483 on Thing-I-Verse) by its creator Cathal Garvey who created it for the DIYbio effort at his local makerspace in Ireland. It has been shared under the Creative Commons license (Attribution – Share Alike) so can be downloaded for free and produced using any available 3D printer you may have in your local school or makerspace. However, if you cannot find a local 3D printer you can have a copy printed for a small fee at Cathal’s Shapeways storefront.
Cathal is a geneticist himself and understands the need for available technologies for separating liquids from their solid components, which we will use in later workshops. This first introduction tested our equipment and provided experience and training for our young learners and their teachers, to support safe operations in the school. I have reproduced many copies of this design using both the original Makerbot Replicator, as well as using the two RepRap kits provided for the book Richard Horne (@RichRap) and I recently wrote called “3D Printing for Dummies.”
Both the MendelMax 2 provided by Makers Tool Works and the Rostock Max provided by John at SeeMeCNC have done very well reproducing the DremelFuge in both PLA and ABS plastic, although the ABS is less brittle when centrifuging samples at very high speeds for long periods of time. I have never lost a DremelFuge while in operation, but the PLA plastic was found to have small fractures radiating outwards from the rotary tool’s spindle connection after two hours of continuous operating at max speed (>20,000 G for the six liquid samples). The pellet of solids collected in two of the micro-centrifuge PCR tubes (1.5mL each) were lost due to failures in the tubes themselves during these tests, so care is needed in the use of centrifuges of any type.
The rotary tool (a corded hand Dremel tool) was operated while clamped securely in a bench vise, while a metal bowl (2L mixing bowl, generic type) shielded the workshop participants while under operation. Eye protection was worn by anyone near the centrifuge in case anything was thrown clear of even these protections, and heavy welder’s gloves were used to adjust the rotary tool’s settings. The other tools used in this workshop (per station) were one rotary tool, one DremelFuge 3D Printed adapter equipped with a rotary cutting wheel shaft, up to six 1.5mL microcentrifuge PCR tubes (any number is fine, just make sure the arrangement is balanced before turning on the rotary tool), and a means to deliver the sample liquids to the tubes (here, we are using inexpensive plastic squeeze-bulb pipettes)
The samples we used during this workshop came from common household liquids with a solid material component – left to right are soy milk, orange juice, lime juice, and salad dressing. In later workshops we will extract human DNA from a cheek swab and use PCR amplification to create a DNA typing sample of sufficient capacity for electrophoresis testing.
.The samples were prepared, weighed and arranged in the DremelFuge to provide a balanced configuration that could be spun at roughly 13,000 rpm for 10 minutes for each sample group during this workshop, to ensure that all participants could complete the exercise.
Afterwards, the solid material had formed the expected pellet in the bottom of each tube while the clear liquids were separated by the centrifugal force the samples had experienced. Samples were taken of each layer of liquid and solid material for testing and exploration using the microscope and standard chemical test strips. One team even used the extracted solids to form a very rudimentary type of battery after their turn, which illustrates the magnificent qualities possible through direct experimentation under careful supervision in comparison to dry book-based lectures.