Holographic laser printing achieves 3D shapes with voids in one shot

Researchers from the University of Utah and The University of Texas at Austin have pioneered a novel 3D printing method that bypasses the layer-by-layer fusion common in additive manufacturing, thereby eliminating issues like leaky seams. This new process utilizes a nanoscale "mask" to diffract laser light into a holographic pattern of the desired object, solidifying the printing material in a single step. The entire printing process can be completed in as little as 7.5 seconds, a remarkable acceleration compared to conventional laser-based printing techniques that often take hours.

Building upon earlier work that demonstrated the printing of microtubule assemblies with diameters as small as 6 micrometers, the team has now achieved more intricate prints, including structures with hollow voids extending along multiple axes. This advancement was detailed in a recent publication in the journal Science Advances. The research, led by Professor Rajesh Menon and lab member Dajun Lin from the University of Utah, involved collaboration with Associate Professors Michael Cullinan and Zachariah A. Page from The University of Texas at Austin.

The printing material is a specially formulated resin composed of crosslinking polymers that harden upon exposure to laser light. The unexposed resin is subsequently washed away, leaving the solidified object. While 2D photolithography uses an opaque mask to block light from unwanted areas, applying this to 3D printing requires the laser to pass through the substrate. A challenge arises from the substrate's imperfect transparency, which can cause laser light to diffract and blur, affecting accuracy.

To overcome this blurring, Menon's group developed a nanopatterned mask that precisely compensates for the substrate's diffraction. This mask directs the laser's energy only to the specific volume of resin intended for curing. Previous demonstrations of this technology produced complex microtubule arrays with voids along their length and width but were limited to "extended 2D" structures, lacking voids along the print's height. The latest research overcomes this limitation by modifying the resin's chemical composition and employing sophisticated computational engineering to design the photomasks. This allows for precise control over light intensity, creating dark regions that prevent curing and thus enabling the formation of internal voids along any axis.

The successful printing of hollow cylinders and cubes demonstrates the technique's capability for creating complex, true 3D structures with internal voids in a matter of seconds. This breakthrough signifies a major step forward in rapid prototyping and the creation of advanced, functional components.