Innovative 3D Printing Technique for Mass Production of Microscale Particles Developed by Researchers

Scientists from Stanford University have discovered a new rapid 3D printing method that can generate as many as one million complex microscale particles per day.

The 3D printing of microscopic structures is a trending area in several fields including drug delivery, microelectronics, and microfluidics. Nevertheless, the scale of production has been limited due to various hurdles. The necessity to manage the supply of light, the movements of the stage and the traits of the resin oftentimes results in a compromise among speed, geometric control, uniformity, and material characteristics.

In order to address these limitations, the researchers from Stanford utilized a resin-based 3D printing methodology known as continuous liquid interface production, or CLIP for short. The scientists integrated this process into a manufacturing line technique to invent a novel method, named roll-to-roll CLIP, or r2rCLIP.

This process enabled the 3D printing, purifying, curing, and removal of sets of micro-scale models to be performed automatically without human intervention, notably improving production speeds. This method is believed to facilitate high-quantity 3D printing of complex microscopic designs, presenting significant potential for use in biomedical, analytical, and advanced materials applications.

“We can now create much more complex shapes down to the microscopic scale, at speeds that have not been shown for particle fabrication previously, and out of a wide range of materials,” explained Jason Kronenfeld, a PhD candidate in the DeSimone lab at Stanford University.

The findings, titled ‘Roll-to-roll, high-resolution 3D printing of shape-specific particles,’ have been published in the academic journal Nature.

Scaling micro-3D printing to mass production

Joseph DeSimone, Sanjiv Sam Gambhir Professor in Translational Medicine at Stanford Medicine, contributed to the co-development of CLIP 3D printing, the technology of which was patented by his company, Carbon, in 2015.

The process of photopolymerization utilized by CLIP 3D printing effectively cures resin into a specific form using UV light. Unlike DLP and SLA technology that cures the resin layer by layer, the CLIP technique employs a continuous 3D printing process that substantially cuts down the manufacturing time.

At the core of this technique is an oxygen-permeable window. This component creates a thin region in the resin at the bottom of the vat where polymerization does not occur. Termed as the ‘dead zone’, this feature averts the curing and adhesion of liquid resin to the crucial projection window. This results in faster 3D printing speeds and aids in the production of more delicate green parts.

Advancing their 3D printing process for high-volume micro-production, the Stanford team replaced the constant build plate of a CLIP 3D printer with a roll-to-roll film alternative that is continuous and modular.

The aluminum-coated polyethylene terephthalate (PET) film commences the process by being fed through the CLIP 3D printer after being tensioned. This step witnesses the creation of hundreds of microscopic shapes right onto the film with the help of the printer. The assembly line of the PET film then transfers the 3D printed shapes to various stations. These stations are automated to perform the tasks of washing, curing, and finally the removal of these shapes. The film, now empty, can be rewound for subsequent use.

The 3D printer possesses the capability to fabricate particles reaching up to 200 µm in size along with feature resolutions of 2.0µm. The prowess of r2rCLIP to 3D print dimensionally complex structures is demonstrated by the researchers by producing a variety of shapes, their geometric complexity graduating gradually. One of these designs was a three-dimensional representation of the DeSimone lab logo, manifesting a buckyball geometry at the micron-scale.

When it comes to conventional micro-3D printing, the job of processing batches of particles is done manually which can be painstakingly slow and labor-intensive. However, making use of a completely automated process, r2rCLIP is able to 3D print as many as one million particles within a single day.

Thanks to this high throughput, it is believed that r2rCLIP could be used for the mass production of components ranging from microrobots and cargo delivery systems, to drug delivery vessels. Indeed, the Stanford team has already experimented with 3D printing both hard and soft particles made of ceramics and hydrogels.

“Our approach is distinctively capable of producing high-resolution outputs while preserving the fabrication pace required to meet the particle production volumes that experts consider essential for various applications,” stated Kronenfeld.

Looking to the future, the Stanford researchers hope that r2rCLIP 3D printing will be more widely adopted by other researchers, industries, and high-value mass-production applications.

Different particle shapes 3D printed using the new process from the Stanford University researchers. Image via Nature.

Expanding Resin 3D Printing to Large-Scale Production

This investigation is aimed at expanding the production of microscale particles. Nonetheless, the feasibility of resin 3D printing for large-scale production, including machine parts, fixtures, dentures, and hearing aids, is also being looked into.

In 2019, researchers at the University of Michigan devised a rapid resin 3D printing procedure that is 100 times quicker than existing commercial technologies. The method, which is comparable to the CLIP approach, uses a dual light source consisting of UV and blue light.

Utilizing a resin mix that includes both photo initiators and inhibitors, the lights can be adjusted to initiate and halt the curing process as necessary. This tactic achieves a similar ‘dead zone’ impact as with CLIP, but without the requirement for a physical window.

The University of Michigan team successfully used this approach to achieve 3D print speeds of approximately 2 m/hour. As a result, the researchers stated that this method could offer value for companies looking to use additive manufacturing in mass production. 

Elsewhere, Israeli start-up Sprybuild recently unveiled its new Stereolithography (SLA) 3D printer featuring a continuous build process on a conveyor belt, which could offer potential in mass production applications. Utilizing a magnetic mechanism, the conveyor belt achieves surface stability while enabling the automatic release of 3D printed parts, reducing downtime and boosting productivity.

During testing, the system successfully 3D printed dental models at a speed of 55 mm/min. However, Sprybuild claims that the 3D printer can reach speeds of up to 150 mm/min, 2.5 times faster than the average commercial resin 3D printer.

One company that has already leveraged resin-based additive manufacturing to achieve mass production is Utah-based 3D printed parts manufacturer Merit3D. Last year, the firm utilized 20 Photocentric Liquid Crystal Magna LCD resin 3D printers to deliver an order for one million 3D printed parts. 

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