Massachusetts Institute of Technology
An example of one of the devices created by the researchers.
MIT researchers have used 3D printing to develop self-heating microfluidic devices, demonstrating a technique which the team says could one day be used to rapidly create cheap, but accurate, tools to detect various diseases.
Microfluidics, miniaturised machines which manipulate fluids and facilitate chemical reactions, can be used to detect disease in small samples of blood or fluids. At-home Covid-19 test kits for example contain a simple type of microfluidic.
The MIT team says that many microfluidic applications require chemical reactions that must be performed at specific temperatures. These more complex devices are outfitted with heating elements made from gold or platinum using an expensive fabrication process.
The team of MIT researchers used multi-material 3D printing to create self-heating microfluidic devices with built-in heating elements, through a single process which the team says was inexpensive. The team generated devices that can heat fluid to a specific temperature as it flows through microscopic channels inside the machine.
The technique is customisable according to the team, so an engineer could create a microfluidic device that heats fluid to a certain temperature or given heating profile within a specific area of the device. The team says the process requires around 2 USD of materials to generate a ready-to-use microfluidic.
The researchers say the process could be especially useful in creating self-heating microfluidics for remote regions of developing countries where clinicians might not have access to the expensive lab equipment required for certain diagnostic procedures.
“Clean rooms in particular, where you would usually make these devices, are incredibly expensive to build and to run. But we can make very capable self-heating microfluidic devices using additive manufacturing, and they can be made a lot faster and cheaper than with these traditional methods. This is really a way to democratise this technology,” said Luis Fernando Velásquez-García, a principal scientist in MIT’s Microsystems Technology Laboratories (MTL) and senior author of a paper describing this new technique.
Velásquez-García spoke to TCT in April 2023 about an MIT project in which researchers created completely 3D printed sensors for satellites. He is joined on the paper for this new process by lead author Jorge Cañada Pérez-Sala, an electrical engineering and computer science graduate student.
The new process utilises multi-material extrusion 3D printing, in which several materials can be dispersed through the printer’s nozzles to build a device. The process is monolithic, which means the device can be produced in one step on the 3D printer, without the need for post-assembly.
The researchers used two materials to create the devices, polylactic acid (PLA) and a modified version of PLA which was cooper nanoparticles mixed into the polymer, which converts the material into an electrical conductor.
“It’s amazing when you think about it because the PLA material is dielectric, but when you put in these nanoparticle impurities, it completely changes the physical properties. This is something we don’t fully understand yet, but it happens and it is repeatable,” said Velásquez-García.
The researchers used this one-step manufacturing process to generate a prototype that could heat fluid by 4 degrees Celsius as it flowed between the input and the output. This technique could enable the team to make devices which would heat fluids in certain patterns or along specific gradients.
Velásquez-García added: “You can use these two materials to create chemical reactors that do exactly what you want. We can set up a particular heating profile while still having all the capabilities of the microfluidic.”
A limitation that comes with this process is that PLA begins to degrade once it reaches around 50 degrees Celsius. The team says that many chemical reactions, such as those used for polymerase chain reaction (PCR) tests, require temperatures of 90 degrees or higher. To precisely control the temperature of the device, the researchers say they would need to integrate a third material that enables temperature sensing.
As well as tackling these limitations in future work, Velásquez-García says he wants to print magnets directly into the microfluidic device. The team says these magnets could enable chemical reactions that require particles to be sorted or aligned.
