Researchers at MIT have made significant progress in addressing the challenge of building an affordable and portable mass spectrometer by utilizing additive manufacturing. They successfully 3D printed a miniature version of a peristaltic pump, a type of vacuum pump, which is approximately the size of a human fist.
The innovative design of the 3D-printed pump allows it to create and maintain a vacuum with significantly lower pressure compared to dry, rough pumps that operate at atmospheric pressure without the need for liquid. The unique design, printed in one pass on a multimaterial 3D printer, ensures that there are no leaks of fluid or gas while minimizing heat generated from friction during the pumping process. This increases the device’s longevity.
The miniature pump holds great potential for incorporation into portable mass spectrometers, particularly for applications such as monitoring soil contamination in remote areas or for geological survey equipment destined for Mars. Its lightweight nature also makes it more cost-effective to launch into space.
Luis Fernando Velásquez-García, a principal scientist in MIT’s Microsystems Technology Laboratories (MTL) and the senior author of the research paper, emphasized the groundbreaking nature of their achievement, attributing its success to the use of 3D printing technology. He expressed that without 3D printing, such progress would not have been feasible.
The team’s work opens up possibilities for the development of highly capable yet affordable mass spectrometers. By addressing the longstanding challenge posed by pumps in mass spectrometry, this advancement paves the way for broader deployment of these devices in various fields. The study was published on April 25 in the journal Additive Manufacturing.
Pump problems
In mass spectrometry, the process involves converting sample atoms into ions by removing electrons as the sample is pumped through the instrument. These ions are then manipulated using an electromagnetic field within a vacuum, allowing their masses to be accurately determined. This mass information is crucial for identifying the constituents of the sample with precision. Maintaining a vacuum environment is essential to prevent collisions between ions and gas molecules, which can disrupt the analysis and lead to false positives.
Peristaltic pumps are commonly employed for pumping liquids or gases that could contaminate the pump’s internal components or require clean handling, such as reactive chemicals or blood. These pumps operate by enclosing the substance within a flexible tube that is looped around a set of rollers. As the rollers rotate, they squeeze the tube against its housing, creating a vacuum effect that draws the fluid or gas through the tube.
However, using peristaltic pumps in mass spectrometers has been limited due to design challenges. The material of the tube tends to shift or redistribute when subjected to the force applied by the rollers, resulting in gaps that cause leaks. Although operating the pump at high speed can mitigate this issue by pushing the fluid through faster than it can leak, it generates excessive heat that can damage the pump, and the gaps still persist. To achieve a complete seal of the tube and create the necessary vacuum for a mass spectrometer, additional force is required to compress the bulged areas, leading to further damage, as explained by Velásquez-García.
An additive solution
The research team led by Velásquez-García approached the design of the peristaltic pump by leveraging additive manufacturing techniques. They reimagined the pump from its core elements, seeking opportunities to enhance it using 3D printing technology. Initially, they utilized a multimaterial 3D printer to fabricate the flexible tube using a special hyperelastic material known for its remarkable deformation resistance.
Through an iterative design process, the researchers introduced notches along the tube’s walls to alleviate stress when compressed. The incorporation of notches eliminated the need for material redistribution to counteract the force exerted by the rollers.
The high precision achievable with 3D printing allowed the team to create notches of the exact size required to eliminate gaps effectively. They also varied the thickness of the tube’s walls, reinforcing them at connector attachment points to further mitigate stress on the material.
To ensure integrity and avoid leaks, the entire tube was printed in one continuous pass using a multimaterial 3D printer. This approach eliminated potential defects introduced during post-assembly. Printing the narrow and flexible tube vertically posed a challenge, as it needed to remain stable throughout the process. To address this, the team developed a lightweight structure that provided stability during printing and could be easily removed without damaging the device.
One significant advantage of employing 3D printing, according to Velásquez-García, is the ability to rapidly prototype and iterate. Unlike traditional clean room manufacturing processes that are time-consuming and costly, 3D printing enables quick fabrication. Design changes can be implemented swiftly, and each print iteration can be a new and improved design. Velásquez-García emphasizes the speed and flexibility offered by 3D printing, which allows for efficient exploration and optimization of the pump design.
Portable, yet performant
Upon testing their final design, the researchers discovered that their 3D-printed pump achieved a vacuum with pressure an order of magnitude lower than that of state-of-the-art diaphragm pumps. This indicates a higher-quality vacuum, which is crucial for optimal performance. Velásquez-García noted that to achieve the same level of vacuum using standard diaphragm pumps, three pumps would need to be connected in series.
In addition to its superior vacuum capabilities, the 3D-printed pump exhibited a maximum temperature of only 50°C, half that of other pumps used in previous studies. It also required only half the force to completely seal the tube, reducing stress on the pump and minimizing potential damage.
Michael Breadmore, a professor in analytical chemistry at the University of Tasmania who was not involved in the research, praised the work for its elegant utilization of multimaterial 3D printing. He highlighted the compact size of the pump, its exceptional vacuum performance, and its ability to exploit the advantages of 3D printing for creating integrated and functional components. Breadmore emphasized that this achievement demonstrates the power of designing and creating in 3D.
Looking ahead, the researchers intend to further decrease the maximum temperature to enhance the pump’s performance. By achieving a lower temperature, the tube can actuate more rapidly, resulting in improved vacuum creation and increased flow rate. Additionally, they plan to 3D print an entire miniaturized mass spectrometer while refining the specifications of the peristaltic pump.
Velásquez-García emphasized that their work challenges the notion that 3D printing necessitates tradeoffs. The team’s success highlights a new paradigm where additive manufacturing offers viable solutions. While it may not address all global challenges, 3D printing proves to be a promising and impactful approach.