Introduction: Micro-centrifuge Open-sourced Biomedical Device
- This an ongoing project that will be updated with community support and further research and instruction.
- The aim of this project is to create open-sourced, modular lab equipment that is easy to transport and built from cheaply sourced parts to assist in the diagnosis of diseases in remote and low infrastructure areas.
- This will be an ongoing open-sourced project with the mission of providing a modular platform for medical devices, which can be easily modified and expanded upon at low cost.
- Initial designs will be for a modular battery and DC motor pack, and micro-centrifuge.
- It will seek the help of the online open-source community to assist with support, modification, and further designs, to target the individual specific needs of healthcare workers in remote and rural locale.
DISCLAIMER: Project is still undergoing design and functionality testing and is not yet suitable for ANY diagnostic or clinical application. Electronics and motors are to be assembled and used at readers own risk.
Step 1: Problem and Design Statements
The lack of access to laboratory and clinical equipment to assist in the diagnosis and treatment of diseases leads to the preventable deaths of many in remote and low infrastructure areas. Specifically, the lack of access to basic reliable centrifuges strips healthcare workers of a vital tool in the fight against blood-borne pathogens such as AIDS and malaria.
To design a micro-centrifuge, and modular battery and DC motor pack, to assist in the diagnosis and treatment of diseases caused by blood-borne pathologies (pathogens and parasites). Utilising additive manufacturing techniques where viable, this design seeks to improve portability and lower economic barriers of life-saving technologies.
Step 2: Design Rationale:
This design is aimed at producing a microcentrifuge suitable for replacement use in rural areas by utilising desktop FDM 3D printing, laser cutting, and hobby grade electronics. In doing so, it is hoped that the device will be accessible to a wide variety of healthcare professionals with varying access to resources.
When designing the centrifuge rotor (part of design that holds test tubes):
- The required G-force for separation of samples is dependant upon the desired sample type, with average forces for separating blood into its constituents ranging 1,000 – 2,000 g (thermofisher.com).
- The calculation of RPM to RFC (G-force), can be calculated using RCF = (rpm)2 × 1.118 × 10-5 × r, where ‘r’ is the radius of the rotor (bcf.technion.ac.il).
Step 3: Design Considerations
Additive manufacturing considerations:
• Poor layer adhesion may occur, resulting in poor tensile strength and part damage
• Properties required, will vary with materials. Some offering good lateral strain and compression strength at a low weight and cost
• Correct settings during the slicing of the G-code must be applied to ensure that the material properties desired are obtained
• Longevity of parts produced using this technique is relatively low when compared to those using more expensive techniques and materials such as CNC milling metals.
• Thermoplastics have a relatively low transition temperature, so a low operating temperature must be maintained (< approx. 80-90 celcius) • Open-sourced 3d printed designs will allow users to modify designs to suit their needs and constraints
Further design constraints:
• Some areas may not have adequate access to power, may have to be powered by basic portable solar, batteries, etc.
• Vibration and balance may be an issue
• Must be able to output high RPM for periods of up to 15 min or more, results in high mechanical stress on some parts
• Users may not be experienced in the use of equipment and will require support to lower technical barrier
Step 4: Initial/Base Module Design
The above design makes best use of space to provide adequate room for internal electronic components and ensures a large enough radius for a variety of centrifuge rotors and tube sizing. The ‘snap together’ style of the design has been chosen to eliminate the need for support material during production and to allow for easy printing, repair, and fabrication in both additive and subtractive manufacturing. Additionally, printing of smaller individual parts will reduce impact of printing failure/error, and allow for a larger variety of printbed sizes to be used.
By taking advantage of a modular design, many different types of centrifugal bowls may be attached to the device. Rapid modifications and production of these parts through additive manufacturing allows for changes to G-force produced, and sample size/type processed. This helps give it an advantage over traditional machines and provides an innovative approach to designing machines around an end user’s needs.Furthermore, the ballast containers provide a chance to add support and dampen vibration
Step 5: Parts List
3d Printed parts: Files will be uploaded to Github and thingiverse and updated asap.
- 1 x Spindle Screw
- 1 x Rotor Nut
- 1 x Lid Nut
- 1 x Main Lid
- 4 x Rotor Body
- 1 x Fixed Angle Rotor
- 4 x Top/Bottom Ballast
- 2 x Side Ballast
Electronics:(Links to products soon)
- Arduino Nano ($8-10)
- Connector Wires (<$0.2)
- Electronic Speed Controller ($8-10)
- Brushless DC Motor 12V ($15-25)
- Potentiometer ($0.1)
- Li-po rechargeable battery ($15-25)
Step 6: Printing of Parts:
All parts are available from github here:
Also available from thingiverse here:
3d Printed parts:
1 x Spindle Screw
1 x Rotor Nut
1 x Lid Nut
1 x Main Lid
4 x Rotor Body
1 x Fixed Angle Rotor
4 x Top/Bottom Ballast
2 x Side Ballast
The general draft settings from Cura, or similar in selected slicer software, are a good guideline for printing of all body and ballast parts.
Step 7: Assembly: First Step
- Prepare the following parts for assembly as shown:
- Centrifuge base
- Component casing
- 4 x rotor body
Step 8: Assembly: Electronic Components
Prepare the following electronic components for testing:
- DC motor and ECS
- Arduino Nano
- Jumper wires
Coding and instruction for the arduino can be found here: https://howtomechatronics.com/tutorials/arduino/ar...
Test motor is running smoothly and responsive to the potentiometer. If it is, then install the electronics into the casing and test the motor runs smooth and with little vibration.
Pictures of exact placement will be added soon.
Step 9: Assembly: Attaching Rotor and Spinner Screw
Gather rotor, rollers, Spinner, and spinner nuts.
Ensure all parts have a good fit. Sanding may help if fit is too tight.
Ensure rotor has a smooth path and doesn't skip or wobble excessively. A flat dish can be printed, or cut from acrylic, to assist in stability if needed.
Once parts have undergone sanding and fitting, attach spinner screw to the motor spindle and secure the rotor with the nuts as shown.
Rotor can be removed for unloading and loading samples, or for changing rotor types.
Step 10: Assembly: Ballast and Lids
Gather top and side ballast containers, these will act as support, weighting, and vibration dampening.
Parts should slot together and stay in place when filled. If needed, parts can be secured together with super glue or similar adhesive.
Main lid over the rotor should fit securely when fastened with the top rotor nut.
Parts should fit as shown in picture.
Step 11: Conclusion
Remote location healthcare workers face the challenge of economic and logistic barriers associated with obtaining and maintaining vital medical, and diagnostic devices and parts. A lack of access to basic equipment such as centrifuges and pump systems can lead to fatal wait times and misdiagnosis.
This design has met the desired outcome in showing that it is feasible to create an open-sourced medical device (a microcentrifuge), using desktop manufacturing techniques and basic electronic components. It can be produced at one tenth the cost of commercially available machines, and easily repaired or disassembled for parts to be made use of in other devices, lowering economic barriers. The electronic components provide constant reliable power for the time required to process most common blood samples, providing better diagnostics than hand powered, or outlet units, in low infrastructure areas. The feasibility of this design has future potential in the development of a modular open-sourced platform of medical devices, using a core set of components to drive various equipment such as peristaltic pumps, or as in this design, microcentrifuges. With the establishment of a library of open sourced files, access to a single FDM printer could be used to produce a range of parts, with little knowledge in design required by the end user. This would eliminate the logistical problems associated with the shipping of basic components, saving time and lives.