We introduce a class of stiffness-tuning polymer composites and carefully examine the influence of electrical activation and temperature on stiffness for a wide range of use cases. The composites are composed of a polycaprolactone matrix embedded with a percolating network of acetylene carbon black or multi-walled carbon nanotubes. This work builds on previous efforts with thermally activated stiffness-switching composites, which can enable reliable, high-switching-ratio stiffness-switching devices that are stiff in the passive state and are not confined to specific geometries or layouts. Here, we systematically investigate the effects of filler type, filler concentration, and matrix polymer molecular weight on the critical properties of the stiffness-switching material. Using these parameters, we develop a composition selection guide, which we use to construct three different stiffness-switching applications: a highly extensible stiffness-switching tendon, a large area moldable sheet, and an electrically healable mechanical fuse.
AbrahamJSharikaTGeorgeSC, et al. (2017) Rheological percolation in thermoplastic polymer nanocomposites. Rheology: Open Access1(1): 102.
2.
AldreteGSBartellSMAldreteA (2013) Reconstructing Ancient Linen Body Armor: Unraveling the Linothorax Mystery. Baltimore, MD: Johns Hopkins University Press.
3.
BarfieldL (1994) The iceman reviewed. Antiquity68(258): 10–26.
4.
BauhoferWKovacsJZ (2009) A review and analysis of electrical percolation in carbon nanotube polymer composites. Composites Science and Technology69(10): 1486–1498.
5.
BilodeauRAKramerRK (2017) Self-healing and damage resilience for soft robotics: a review. Frontiers in Robotics and AI4: 48.
6.
BucknerTLWhiteELYuenMC, et al. (2017) A move-and-hold pneumatic actuator enabled by self-softening variable stiffness materials. In: IEEE international conference on intelligent robots and systems, Vancouver, BC, Canada, 24–28 September, pp. 3728–3733. New York: IEEE.
7.
DillerSBCollinsSHMajidiC (2018) The effects of electroadhesive clutch design parameters on performance characteristics. Journal of Intelligent Material Systems and Structures29: 3804–3828.
8.
FlowersPFReyesCYeS, et al. (2017) 3D printing electronic components and circuits with conductive thermoplastic filament. Additive Manufacturing18: 156–163.
9.
HammondFLIIIWuFAsadaHH (2018) Variable stiffness pneumatic structures for wearable supernumerary robotic devices. In BicchiABurgardW (eds) Robotics Research, vol. 1. Berlin: Springer, pp. 201–217.
10.
HauserSRobertsonMIjspeertA, et al. (2017) JammJoint: a variable stiffness device based on granular jamming for wearable joint support. IEEE Robotics and Automation Letters2(2): 849–855.
11.
ImamuraHKadookaKTayaM (2017) A variable stiffness dielectric elastomer actuator based on electrostatic chucking. Soft Matter13(18): 3440–3448.
12.
KhanWSharmaRSainiP (2017) Carbon nanotube-based polymer composites: synthesis, properties and applications. In: BerberMHafezIH (eds) Carbon Nanotubes: Current Progress of Their Polymer Composites. London: InTech, pp. 1–45.
13.
KotaAKCiprianoBHDuesterbergMK, et al. (2007) Electrical and rheological percolation in polystyrene/MWCNT nanocomposites. Macromolecules40(20): 7400–7406.
14.
LaibleRC (1982) Ballistic Materials and Penetration Mechanics (The American Journal of Forensic Medicine and Pathology). Amsterdam: Elsevier.
15.
LeHMDoTNCaoL, et al. (2017) Towards active variable stiffness manipulators for surgical robots. In: IEEE international conference on robotics and automation, Singapore, 29 May–3 June, pp. 1766–1771. New York: IEEE.
16.
LiJTanakaH (2018) Rapid customization system for 3D-printed splint using programmable modeling technique—a practical approach. 3D Printing in Medicine4: 5.
17.
LiangJZDuanDRTangCY, et al. (2014) Tensile properties of polycaprolactone/nano-CaCO3 composites. Journal of Polymer Engineering34(1): 69–73.
18.
LiangJZZhouLTangCY, et al. (2013) Crystallization properties of polycaprolactone composites filled with nanometer calcium carbonate. Journal of Applied Polymer Science128(5): 2940–2944.
19.
LipatovYSBabichVFRosovizkyVF (1976) Effect of filler on the relaxation time spectra of filled polymers. Journal of Applied Polymer Science20(7): 1787–1794.
20.
LiuHLiYDaiK, et al. (2015) Electrically conductive thermoplastic elastomer nanocomposites at ultralow graphene loading levels for strain sensor applications. Journal of Materials Chemistry C4(1): 157–166.
21.
LuoHZhouXXuY, et al. (2018) Multi-stimuli triggered self-healing of the conductive shape memory polymer composites. Pigment and Resin Technology47(1): 1–6.
22.
MalkinAYPetrieCJS (1997) Some conditions for rupture of polymer liquids in extension. Journal of Rheology41(1): 1–25.
23.
MantiMCacuccioloVCianchettiM, et al. (2016) Stiffening in soft robotics: a review of the state of the art. Robotics and Automation Magazine23(3): 93–106.
24.
MarinhoBGhislandiMTkalyaE, et al. (2012) Electrical conductivity of compacts of graphene, multi-wall carbon nanotubes, carbon black, and graphite powder. Powder Technology221: 351–358.
Mohammadi NasabASabzehzarATatariM, et al. (2017) A soft gripper with rigidity tunable elastomer strips as ligaments. Soft Robotics4(4): 411–420.
27.
NarangYSDegirmenciAVlassakJJ, et al. (2018) Transforming the dynamic response of robotic structures and systems through laminar jamming. IEEE Robotics and Automation Letters3(2): 688–695.
28.
NorooziN (2013) Rheology and Processing of Biodegradable Poly(Epsilon—Caprolactone) Polyesters and Their Blends with Polylactides. Vancouver, BC, Canada: The University of British Columbia.
29.
PenuCHuG-HFernandezA, et al. (2012) Rheological and electrical percolation thresholds of carbon nanotube/polymer nanocomposites. Polymer Engineering and Science52: 2173–2181.
SaidGZ (2014) Orthopaedics in the dawn of civilisation, practices in ancient Egypt. International Orthopaedics38(4): 905–909.
35.
SchubertBEFloreanoD (2013) Variable stiffness material based on rigid low-melting-point-alloy microstructures embedded in soft poly(dimethylsiloxane) (PDMS). RSC Advances3(46): 24671–24679.
36.
ShanWDillerSTutcuogluA, et al. (2015) “Rigidity-tuning conductive elastomer.”Smart Materials and Structures24(6): 065001.
37.
ShanWLuTMajidiC (2013) Soft-matter composites with electrically tunable elastic rigidity. Smart Materials and Structures22(8): 085005.
38.
StarýZPappMBurgheleaT (2015) Deformation regimes, failure and rupture of a low density polyethylene (LDPE) melt undergoing uniaxial extension. Journal of Non-Newtonian Fluid Mechanics219: 35–49.
39.
SteeleV (2003) The Corset: A Cultural History. New Haven, CT: Yale University Press.
40.
TakahashiRSunTLSaruwatariY, et al. (2018) Creating stiff, tough, and functional hydrogel composites with low-melting-point alloys. Advanced Materials30(16): e1706885.
41.
TonazziniAMintchevSSchubertB, et al. (2016) Variable stiffness fiber with self-healing capability. Advanced Materials28: 10142–10148.
42.
TonazziniAShintakeJRognonC, et al. (2018) Variable stiffness strip with strain sensing for wearable robotics. In: IEEE international conference on soft robotics (RoboSoft), Livorno, 24–28 April, pp. 485–490. New York: IEEE.
43.
WangLYangYChenY, et al. (2018) Controllable and reversible tuning of material rigidity for robot applications. Materials Today21(5): 563–576.
44.
WenMSunXSuL, et al. (2012) The electrical conductivity of carbon nanotube/carbon black/polypropylene composites prepared through multistage stretching extrusion. Polymer53(7): 1602–1610.
45.
XuXGaoCZhengQ, et al. (2007) Linear/nonlinear rheological properties and percolation threshold of polydimethylsiloxane filled with calcium carbonate. Journal of the Society of Rheology, Japan35(5): 283–291.
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
