This device, which is only the size of a human fist, performed better than other types of pumps at creating and maintaining dry vacuum, which is key for enabling a mass spectrometer to effectively determine the molecules in a sample.
Newswise —
Constructing a low-cost, portable mass spectrometer capable of being utilized in remote areas remains challenging due to the intricacy of downsizing the essential vacuum pump, despite the fact that mass spectrometers are highly accurate chemical analyzers with various applications, such as examining the safety of drinking water and identifying toxins in a patient's bloodstream.
By using additive manufacturing, MIT scientists have made a significant stride towards addressing this issue. They have created a miniature edition of a peristaltic pump, a type of vacuum pump, with 3D printing technology, which is roughly the size of a human fist.
This pump is capable of generating and sustaining a vacuum with a pressure level that is ten times lower than that of another commonly used pump. Its distinctive construction, which can be 3D printed in a single pass using a multimaterial printer, inhibits fluid or gas leakage while also reducing the heat produced by friction during the pumping process. As a result, the device's lifespan is extended.
The miniature peristaltic pump holds great potential for integration into portable mass spectrometers that are deployed to monitor soil contamination in remote regions of the world. Moreover, it could be an ideal component of geological survey equipment bound for Mars as it is lightweight and less expensive to launch into space.
Luis Fernando Velásquez-García, the senior author of the paper describing the new pump, and a principal scientist in MIT's Microsystems Technology Laboratories (MTL), stated that the innovative 3D-printed peristaltic pump is a game-changer for mass spectrometers due to its exceptional capabilities and affordability. The problem of pumps has always been a major hurdle in the development of mass spectrometers. However, he added that this breakthrough is only possible because of 3D printing technology. If they had gone about it the conventional way, they wouldn't have achieved anything close to this level of success.
In addition to Luis Fernando Velásquez-García, the paper's senior author, the team included Han-Joo Lee, a former postdoctoral researcher at MIT, and Jorge Cañada Pérez-Sala, a graduate student in electrical engineering and computer science. The paper, which was published today, can be found in Additive Manufacturing.
Pump problems
In a mass spectrometer, a sample is pumped through the device and then subjected to an electric charge to transform its atoms into ions. An electromagnetic field is then utilized to manipulate these ions in a vacuum to determine their masses, enabling the identification of the molecules present in the sample. The vacuum is critical to maintain because if the ions come into contact with gas molecules from the atmosphere, their behavior will be altered, leading to inaccurate results.
Peristaltic pumps are frequently employed to transfer fluids or gases that could taint the pump's components, such as reactive chemicals. The substance is entirely enclosed within a flexible tube that is wrapped around a set of rollers. The rollers grip the tube against its housing while rotating, compressing it. The compressed portions of the tube widen in the rollers' wake, creating a vacuum that draws the fluid or gas through the tube.
Despite creating a vacuum, design issues have hindered the application of peristaltic pumps in mass spectrometers. When the rollers apply force to the tube, the tube material tends to shift, resulting in gaps that lead to leaks. While this problem can be resolved by operating the pump at high speeds, which forces the fluid to move faster than it can escape, it generates excessive heat that damages the pump, and the gaps persist. To create the vacuum required for a mass spectrometer and completely seal the tube, additional force must be applied to squeeze the bulging areas, causing more damage, according to Velásquez-García.
An additive solution
Velásquez-García and his team approached the peristaltic pump design in a new way, exploring how they could leverage additive manufacturing to enhance it. To begin, they utilized a multimaterial 3D printer to manufacture the flexible tube from a unique hyperelastic material capable of enduring significant deformation.
The team then engaged in an iterative design process and discovered that incorporating notches into the walls of the tube would lower the stress on the material when squeezed. When notches are present, the tube material does not need to shift to counterbalance the force from the rollers.
Thanks to the precision offered by 3D printing, the scientists could create the ideal notch size required to eliminate the gaps. Moreover, they were able to adjust the thickness of the tube, making the walls stronger in locations where connectors attach, further reducing material stress.
The researchers printed the complete tube in a single step with a multimaterial 3D printer. This is significant because post-assembly can introduce faults that can cause leaks. However, printing the narrow, flexible tube vertically posed a challenge, as it had to be kept from wobbling during the printing process. Ultimately, the team developed a lightweight structure that supports the tube throughout printing but can be easily removed without causing any harm to the device.
“One of the key advantages of using 3D printing is that it allows us to aggressively prototype. If you do this work in a clean room, where a lot of these miniaturized pumps are made, it takes a lot of time. If you want to make a change, you have to start the entire process over. In this case, we can print our pump in a matter of hours, and every time it can be a new design,” Velásquez-García says.
Portable, yet performant
Upon testing the ultimate model, the scientists observed that it could generate a vacuum with pressure ten times lower than that produced by advanced diaphragm pumps. This results in a superior-quality vacuum. Velásquez-García stated that to achieve the same pressure as the novel pump, three standard pumps would have to be connected in series.
The pump attained a maximum temperature of 50 degrees Celsius, which is half that of the state-of-the-art pumps used in other studies, and it only needed half as much force to fully seal the tube.
The researchers have future plans to investigate methods to decrease the maximum temperature even further, which could enhance the tube's ability to actuate more rapidly, resulting in a superior vacuum and greater flow rate. They are also striving to manufacture an entire miniaturized mass spectrometer using 3D printing technology. While working on the device, they will continue to fine-tune the peristaltic pump's specifications.
Velásquez-García expressed that there is a common misconception that 3D printing involves a tradeoff. However, he stated that their research demonstrated the opposite. According to him, 3D printing is a new paradigm that has proven to be a viable solution. Although additive manufacturing may not solve every problem, it is a solution that has a promising future.
This work was supported, in part, by the Empiriko Corporation.
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Written by Adam Zewe, MIT News Office
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