Additive Manufacturing

JUL 2018

ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.

Issue link: https://am.epubxp.com/i/1000502

Contents of this Issue

Navigation

Page 36 of 60

JULY 2018 Additive Manufacturing FEATURE / Active Materials 34 By Brent Donaldson Solving a Materials Challenge in Soft Robotics Broadly speaking, humans have focused our engineering on brute-force mechanical processes because we've lacked the technical capacity to mimic nature. This isn't for a lack of imagination on our part. Leonardo da Vinci modeled his sche- matics for human flight based on the observations of birds back at the start of the 16th century. But the technological capability to engineer and manufacture the complex geometries and me- chanics of living organisms—the natural geometries, material properties and mechanics that have evolved and improved over the course of eons—has been largely absent until recent inno- vations in materials development and additive manufacturing. This nature-mimicking concept, called biomimetics, inspired a recent breakthrough made by researchers work- ing at the University of Minnesota (UofM) in the field of soft robotics. In an article published earlier this year in the journal Extreme Mechanics Letters, lead researcher and UofM Ph.D. candidate Ghazaleh Haghiashtiani helped demonstrate that, for the first time, dielectric elastomer actuators (DEAs) can be fully 3D printed and layered with soft ionic hydrogel- elastomer hybrid material systems. That's a lot to unpack, but this capa- bility holds promise for printing entire soft robots made from a material analogous to human skin—including its ability to carry and respond to electrical stimuli. The materials at the center of Haghiashtiani's research are ionic hydrogel-elastomer hybrids, formed by layering ionic hydrogels (soft, stretchable, transparent and conductive materials in which ions carry charges as opposed to electrons in conventional electrode components) and silicone-based dielectric elastomers (a type of electroactive polymer) in succes- sion. When layered in this manner, this hybrid material system results in a structure that replicates the skin's dermal and epi- dermal layers. While these materials have been researched and developed for years, never before have they been subject to 3D printing for fabricating functional actuators, largely because of the postprocessing necessary to bond the hydrogel inks (which are hydrophilic, i.e. can be mixed with or dissolved by water) with silicone-based materials (which are hydrophobic, i.e. repel water). Haghiashtiani and her team applied a chemical treatment strategy on the silicone surface (with a solution including benzophenone photoinitiator), along with exposure to UV light, to create graft Ghazaleh Haghiashtiani is a Ph.D. can- didate from the University of Minnesota whose research helped demonstrate that, for the first time, dielectric elastomer ac- tuators can be fully 3D printed and layered with soft ionic hydrogel-elastomer hybrid material systems. This capability holds promise for printing entire soft robots made from a material analogous to human skin— including its ability to carry and respond to electrical stimuli. A team from the University of Minnesota and the Army Research Lab has developed processes for fully 3D printing soft dielectric elastomer actuators without postprocessing steps.

Articles in this issue

Archives of this issue

view archives of Additive Manufacturing - JUL 2018