3D Printing Flexible Materials Now Possible With Droplet-Based System

Engineers pioneered a 3D printing technique using microfluidics.
Derya Ozdemir

Engineers are upping the 3D printing game by pushing the boundaries in new ways, and now, a team of researchers from the University of California, Davis, have something new up their sleeve.

They have developed a new way of 3D printing that allows for finely tuned flexible materials to be printed thanks to a droplet-based, multiphase microfluidic system.

The approach works so well that they were able to efficiently print materials with potential applications in soft robotics, tissue engineering, and wearable technology.


You might be familiar with 3D printing, however, may not know the itty bitty details. Here is how it goes for a traditional extrusion-based 3D printer: the material used for printing is pushed through a nozzle and joined to make the structure repeatedly until the end product forms, making it an efficient and cost-effective process.

However, as you'd imagine, this makes printing stuff made of more than one material and at the right softness rather, quite literally, hard

Nozzle and glass capillary microfluidic device similarity

This is where Jiandi Wan, assistant professor of chemical engineering at UC Davis, enters the story.

Having noticed this nozzle was similar to the glass capillary microfluidic devices, which have multiple nozzles placed inside of each other and also happened to be studied at his lab, he thought, "Most extrusion-based 3D printers use very simple nozzles and since we had already developed these glass microfluidics, we thought, 'why not apply it to 3D printing?'"

A multiphase drip system

That was what Wan, UC Davis graduate student Hing Jii Mea and Luis Delgadillo, University of Rochester, did, more specifically, developing a device that uses a multiphase drip system to encapsulate droplets of a water-based solution containing polyethylene glycol diacrylate (PEGDA) in a silicon-based organic polymer called polydimethylsiloxane (PDMS).

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The dripper makes tiny droplets of the PEGDA with PDMS flowing around, and the droplets are evenly inserted into the PDMS, with both materials flow onto the structure that's being printed.

The degree of flexibility can be adjusted

PEDGA diffuses out the droplets and softens the PDMS, hence making it more flexible. Wan said, "You can also encapsulate other chemicals in the droplets to make the overall matrix much softer or harder."

This droplet-based 3D printing technique can also produce flexible porous objects and the flexibility can be easily tuned by changing the droplet size and flow rate. This alone gives researchers around the globe a wide range of options that are just too difficult with conventional methods. 

A wide variety of options

The team is looking into potential applications and other combinations of materials they can use to tweak the 3D printed products.

Wan says, "I think this will open a new area of research since applying the established microfluidics technology to 3D printing represents a new direction to go."

The work was published in the Proceedings of the National Academy of Sciences.

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