Chemists and mechanical engineers from the research groups of Timothy Long and Christopher Williams collaborated on this project . construction , around the latex particles to hold them in place ? This way , the latex could maintain its great structure , and Scott could add photoinitiators and other compounds to the latex to enable 3D-printing with ultraviolet ( UV ) light .
“ When designing the scaffold , the biggest thing you have to worry about is stability of everything ,” Scott said . “ It took a lot of reading , even stuff as basic as learning why colloids are stable and how colloidal stability works , but it was a really fun challenge .”
Novel processing development in engineering
While Scott tinkered with the liquid latex , Meenakshisundaram had to figure out how to correctly print the resin . The researchers chose to use a process called vat photopolymerization , in which the printer uses UV light to cure , or harden , a viscous resin into a specific shape .
Needing a printer capable of printing high-resolution features across a large area , Meenakshisundaram built a new printer . He and Williams , his advisor , came up with the idea to scan the UV light across a large area , and in 2017 , they filed a patent for the printer .
Even with the custom printer , the fluid latex particles caused scattering outside of the projected UV light on the latex resin surface , which resulted in printing inaccurate parts , so Meenakshisundaram devised a second novel idea . He embedded a camera onto the printer to capture an image of each vat of latex resin . With his custom algorithm , the machine is able to “ see ” the UV light ’ s interaction on the resin surface and then automatically adjust the printing parameters to correct for the resin scattering to cure just the intended shape .
“ The large-area scanning printer was a concept I had , and Viswanath made it into reality in short order ,” Williams said . “ Then Viswanath came up with the idea of embedding a camera , observing how the light interacts with the material , and updating the printing parameters based on his code . That ’ s what we want from our Ph . D . students : We provide a vision , and they accomplish that and grow beyond as an independent researcher .”
Meenakshisundaram and Scott discovered their final 3D-printed latex parts exhibited strong mechanical properties in a matrix known as a semi-interpenetrating polymer network , which hadn ’ t been documented for elastomeric latexes in the prior literature .
“ An interpenetrating polymer network is like catching fish in a net ,” Meenakshisundaram said . “ The scaffold gives it a shape . Once you put that in the oven , the water will evaporate , and the tightly coiled polymer chains can relax , spread or flow , and interpenetrate into the net .”
Molecules-to-manufacturing approach
The novel advances in both materials development and processing highlight the interdisciplinary environment fostered between the two groups .
Long and Williams both credited their counterpart ’ s expertise for making the collective breakthrough possible .
“ My philosophy is these types of innovations are only achievable when you partner with people who are very different from you ,” Long said .
The two professors said 3-D printed latex provides the conceptual framework for printing a range of unprecedented materials from rigid plastics to soft rubbers , which have been unprintable until now .
“ When I was a graduate student working on this technology , we were excited to get unique performance from the shapes we could create , but the underlying assumption was we had to make do with very poor materials ,” Williams said . “ What ’ s been so exciting about this discovery with Tim ’ s group is being able to push the boundary of what we assumed was the limit of a printed material ’ s performance .”
VIRGINIA TECH MECHANICAL ENGINEERING ANNUAL REPORT • 2019-2020 • RESEARCH 25