3D printing has been around for at least 25 years, but it is only recently that it has started to go mainstream and given innovative researchers a tool with which to get creative. Now, Randall Erb and colleagues at Northeastern University are using magnetic fields to print detailed geometries from fiber-reinforced composite materials with the highest resolution to date. 

One possible future application of this technology could be the fabrication of medical devices, such as catheters for use in neonatal care. As such, the team is working as a subcontractor under funding awarded to N2 Biomedical LLC of Bedford, Massachusetts by the Eunice Kennedy Shriver National Institute Of Child Health & Human Development of the National Institutes of Health under Award Number 1R41HD086043.

Almost half a million babies are born prematurely in the USA alone and their wellbeing relies on a range of tubes and catheters to deliver air to their lungs, as well as nutrients, fluids, and medications to their bodies and to remove urine. Standard catheters come only in set shapes and sizes and are not necessarily suitable for a particular baby.

"With neonatal care, each baby is a different size, each baby has a different set of problems," explains Erb. "If you can print a catheter whose geometry is specific to the individual patient, you can insert it to a certain critical spot, you can avoid puncturing veins, and you can expedite delivery of the contents."

A first step in the development of this technology is to demonstrate the necessary control in 3D printing. Erb and his colleagues have now used magnetic fields to shape composite materials - polymer-ceramic blends - to assist the 3D printing process and control the flow of ceramic fibers, lightly dusted with magnetic iron oxide. This allowed them to make 3d composite objects that show remarkable strength, stiffness. These products also show new mechanical properties such as programmable fracture toughness, Erb told us. "We [now] have the ability to manipulate crack paths through failing materials," he explains. [Nature Commun, 2015, 6, online DOI: 10.1038/ncomms9641]

An ultralow magnetic field is sufficient to align the ceramic fibers within individual sections of the composite material immersed in liquid polymer to be 3D printed to a very specific device design. "Stereolithography then builds the product, layer by layer, using a computer-controlled projector to cure the polymer.

That control will be critical if one is crafting devices with complex architectures, such as customized miniature biomedical devices. Within a single patient-specific device, the corners, the curves, and the holes must all be reinforced by ceramic fibers arranged in just the right configuration to make the device durable. "We are following nature's lead," explains team member Joshua Martin, "By taking really simple building blocks but organizing them in a fashion that results in really impressive mechanical properties."

Until now there has been a gap between design and practical production. 3D printing with composite materials and magnetic control is filling that gap, the team suggests.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the bestselling science book "Deceived Wisdom".