Mobilefuge: A low-cost, portable, open source, 3D-printed centrifuge that can be used for purification of saliva samples to detect SARS-CoV2

Published: 01-02-2021| Version 1 | DOI: 10.17632/chm9f2c588.1
Ganga Chinna rao Devarapu


One of the best ways to contain the spread of COVID-19 is frequent testing of as many people as possible and timely isolation of uninfected personnel from infected personnel. However, the cost of massive testing is not affordable in many countries. The existing technologies might not be scalable to offer affordable and timely testing for millions of people. To address this issue, novel testing methods based on Loop-Mediated Isothermal Amplification (LAMP) were proposed that are more sensitive, require less reagents and can work with saliva samples instead of more tedious nasal swabs. As a result, LAMP based protocols can make it possible to drive the cost down to one dollar per test. These LAMP based methods require a centrifuge device, mostly for separation of viral particles from reaction inhibitors in saliva samples. However, centrifuge is neither accessible nor affordable in many resource limited settings, especially during this pandemic situation when normal supply chains are heavily disrupted. To overcome these challenges, we invented a low-cost centrifuge that can be useful for carrying out low-cost LAMP based detection of SARS-Cov2 virus in saliva. The 3D printed centrifuge (Mobilefuge) is portable, robust, stable, safe, easy to build and operate. The Mobilefuge doesn't require soldering or programming skills and can be built without any specialised equipment, yet practical enough for high throughput use. More importantly, Mobilefuge can be powered from widely available USB ports, including mobile phones and associated power supplies. This allows the Mobilefuge to be used even in off-grid and resource limited settings. We believe that our invention will aid the efforts to contain the spread of COVID-19 by lowering the costs of testing equipment. Apart from the COVID-19 testing, the Mobilefuge can have applications in the field of biomedical research and diagnostics.


Steps to reproduce

The enclosure for the Mobilefuge consists of three parts: jar, top lid, and bottom lid. The top and bottom lids are locked to the main jar through the threads which makes the Mobilefuge’s assembly easy. This enclosure design is adopted from jar and lid design in Ref. [42]. The main jar has a spiral placeholder (adopted from Ref. [43]) to hold the USB fan motor in place and helps in stabilising the motor vibrations [33]. The top lid provides safety by protecting in case centrifuge tubes or its contents escape from the rotor while the bottom lid provides room for the USB plug. The rotor of the Mobilefuge is adopted from an earlier centrifuge design in Ref. [40] to press-fit to the USB motor axis and hold two centrifuge tubes. All the above mentioned CAD parts are designed using open-source parametric CAD software OpenScad [44]. These 3D-designs are then exported as STL files and which are further translated into a list of instructions to the 3D-printer, i.e. G Code by using a CURA software which slices the 3D model into 2D layers. These G-codes are sent for 3D printing with a Monoprice select Mini V2 3D-printer [45] using PLA material with following settings: 10% infill and support structure. Support structures are removed after the objects are 3D printed. The cost of these 3D-printed parts is estimated assuming a $22.99 per a kg spool of PLA material [46].