Page 64 - Plastcs News January 2019

teChnoLogy

3D printing 100 times faster with Sticky Situations A Boon For

light than conventional process Polymer Science

D printing could change the game for relatively small n a study published in the journal Scientific Reports,
3manufacturing jobs, producing fewer than 10,000 Iscientists in Japan report a method to make industrial
identical items. University of Michigan researchers have polymers sticky without the need for adhesives. Being
shown that Rather than building up plastic filaments layer lightweight, strong and unreactive, polymers such
by layer, a new approach to 3D printing lifts complex as plastic and rubber are useful in many aspects of
shapes from a vat of liquid at up to 100 times faster than modern life. However, these polymers must be treated
conventional 3D printing processes. Timothy Scott, U-M with corrosive chemicals or adhesives to help them
associate professor of chemical engineering co-led the to attach to other materials. In the present study,
development of the new 3D printing approach with Mark researchers led by Assistant Professor Yuji Ohkubo of
Burns, the T.C. Chang Professor of Engineering at U-M. Osaka University, Japan, found a way to create ‘sticky’
polydimethlysiloxane (PDMS), a silicon-based polymer,
and ‘sticky’ plastic polytetrafluoroethylene (PTFE) by
modifying the surfaces of both materials.
PTFE was treated with plasma at 200 degrees Celsius,
which revealed oxygen-containing functional groups on
its surface. On the other hand, PDMS was bombarded with
a plasma jet, produced by forcing nitrogen or air plasma
through a small hole. The plasma jet breaks the silicon-
carbon bonds on the surface and converts them to silanol.
Under high pressure, hydrogen and covalent bonds form
between silanol and the oxygen-containing functional
groups on the treated PTFE, thereby stitching PDMS
Their method solidifies the liquid resin using two lights and PTFE together even in the absence of adhesives.
to control where the resin hardens and where it stays The combined
fluid. This enables the team to solidify the resin in more ma t e ria ls
sophisticated patterns. They can make a 3D bas-relief al s o dis pl ay
in a single shot rather than in a series of 1D lines or 2D s yner gis tic
cross-sections. Their printing demonstrations include a properties such
lattice, a toy boat and a block M.By creating a relatively as increased
large region where no solidification occurs, thicker resins ch e mica l
potentially with strengthening powder additives can be resistance and
used to produce more durable objects.
better repulsion
The method also bests the structural integrity of filament o f dir t. In
3D printing, as those objects have weak points at the addition, if polymer manufacturers would like to fabricate
interfaces between layers. You can get much tougher, a transparent final product, PTFE can be replaced by
much more wear-resistant materials," Scott said. An perfluoroalkoxy alkane. The team further showed that
earlier solution to the solidification-on-window problem when the reverse side of the PDMS is also subjected to
was a window that lets oxygen through. The oxygen the plasma jet treatment, it can bond to copper and
penetrates into the resin and halts the solidification near even glass. Like an extremely strong double-sided tape,
the window, leaving a film of fluid that will allow the newly this three-layer sandwich allows the polymers to adhere
printed surface to be pulled away.By replacing the oxygen cleanly to other useful materials. “PDMS is widely used
with a second light to halt solidification, the Michigan in medicine, for example in microfluidic chips. There
team can produce a much larger gap between the object could be huge benefits in making both PTFE and PDMS
and the window perhaps millimeters thick allowing resin more versatile for medical and food technologies through
to flow in thousands of times faster. The key to success is adhesive-free adhesion,” said study co-author Professor
the chemistry of the resin. Katsuyoshi Endo of Osaka University.

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