Developing a UV-Curable, Environmentally Benign and Degradable Elastomer for Soft Robotics
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.133
Developing a UV-Curable, Environmentally Benign and Degradable Elastomer for Soft Robotics Jacob Rueben1*, Stephanie Walker1*, Stephen Huhn1, John Simonsen1, and Yiğit Mengüç1 Oregon State University, 204 Rogers Hall, Corvallis, OR 97331, U.S.A.
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*authors did equal work
ABSTRACT
This paper introduces preliminary work on a UV-curable, environmentally benign and degradable elastomer, poly(glycerol sebacate itaconate), or PGSI, for use in soft robotics. A onepot, solvent-free synthesis route using safe and inexpensive chemical reagents was developed to enable easy adoption into soft robotics labs. Material characterization of non-aged PGSI samples gave: ultimate tensile strength (UTS) ranging from 134 to 193 kPa with moduli ranging from 57 to 131 kPa and elongations at break ranging from 105 to 137 % (12 samples from 6 batches tested), and resilience values ranging from 73 to 82 % (3 samples from 3 batches tested). FTIR analysis showed a possible decrease in carbon-carbon double bonds after UV curing, evidencing a decrease in itaconic acid methylene groups from photoinitiated free radical cross-linking. NMR on the pre-polymer suggested incorporation of itaconic acid into the main polymer chain and evidence of heterogeneity of the polymer backbone resulting from glycerol bonding. An example molded soft pocket pneumatic actuator is created and briefly characterized. With further development, PGSI can be a degradable material to incorporate into temporary soft robots.
INTRODUCTION Soft robotics relies on the material properties of elastomers to generate vastly different motion profiles than existing stiff robots [1, 2] and can be used for grasping delicate objects [3] or squeezing through small spaces [4]. The material space for soft robotics, however, has mostly been limited to elastomers that do not degrade. Designing for robot degradability opens soft robotics to new industries reliant on the temporary properties of the elastomer and its components, including environmental or human safety (temporary sensing or medicine), and military stealth technologies (DARPA’s ICARUS). Biodegradable and renewable elastomeric materials have recently become a larger area of interest due to their applications in medicine [5, 6], and more recently, soft robotics [7, 8]. Biodegradable polymers of interest include natural rubber, poly(1,8-octanediol-co-citric acid) [5], alginate-based supramolecular ionic polyurethanes (ASPUs) [9], and poly(glycerol sebacate) [10]. Poly(glycerol sebacate) (PGS), was used as a degradable polymer in SPA manufacturing due to its relatively simple synthesis process and favorable mechanical properties [7, 10]. PGS has been made into a UV curing polymer, poly(glycerol sebacate) acrylate (PGSA) [11], enabling fast fabrication from stereolithography (SLA).
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