Thermal actuation is a common actuation method for soft robots. However, a major limitation is the relatively slow actuation speed. Here we report significant increase in the actuation speed of a bimorph thermal actuator by harnessing the snap-through instability. The actuator is made of silver nanowire/polydimethylsiloxane composite. The snap-through instability is enabled by simply applying an offset displacement to part of the actuator structure. The effects of thermal conductivity of the composite, offset displacement, and actuation frequency on the actuator speed are investigated using both experiments and finite element analysis. The actuator yields a bending speed as high as 28.7 cm−1/s, 10 times that without the snap-through instability. A fast crawling robot with locomotion speed of 1.04 body length per second and a biomimetic Venus flytrap were demonstrated to illustrate the promising potential of the fast bimorph thermal actuators for soft robotic applications.
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References
1.
RusD, TolleyMT. Design, fabrication and control of soft robots. Nature, 2015; 521:467–475.
ChenL, LiuC, LiuK, et al.High-performance, low-voltage, and easy-operable bending actuator based on aligned carbon nanotube/polymer composites. ACS Nano, 2011; 5:1588–1593.
22.
KimH, LeeH, HaI, et al.Biomimetic color changing anisotropic soft actuators with integrated metal nanowire percolation network transparent heaters for soft robotics. Adv Funct Mater, 2018; 28:1801847.
23.
HawkesE, AnB, BenbernouNM, et al.Programmable matter by folding. PNAS, 2010; 107:12441–12445.
24.
YaoS, YangJ, PobleteFR, et al.Multifunctional electronic textiles using silver nanowire composites. ACS Appl Mater Interfaces, 2019; 11:31028–31037.
25.
LeeJW, XuR, LeeS, et al.Soft, thin skin-mounted power management systems and their use in wireless thermography. PNAS, 2016; 113:6131–6136.
26.
ShinB, HaJ, LeeM, et al.Hygrobot: a self-locomotive ratcheted actuator powered by environmental humidity. Sci Robot, 2018; 3:eaar2629.
27.
WangW, LeeJ-Y, RodrigueH, et al.Locomotion of inchworm-inspired robot made of smart soft composite (SSC). Bioinspir Biomim, 2014; 9:046006.
28.
SinghV, BougherTL, WeathersA, et al.High thermal conductivity of chain-oriented amorphous polythiophene. Nat Nanotechnol, 2014; 9:384–390.
29.
ParkHS, WangQ, ZhaoX, et al.Electromechanical instability on dielectric polymer surface: modeling and experiment. Comput Methods Appl Mech Eng, 2013; 260:40–49.
30.
HanM, WangH, YangY, et al.Three-dimensional piezoelectric polymer microsystems for vibrational energy harvesting, robotic interfaces and biomedical implants. Nat Electron, 2019; 2:26–35.
31.
ChenT, BilalOR, SheaK, et al.Harnessing bistability for directional propulsion of soft, untethered robots. PNAS, 2018; 115:5698–5702.
32.
OverveldeJT, KloekT, D'haenJJ, et al.Amplifying the response of soft actuators by harnessing snap-through instabilities. PNAS, 2015; 112:10863–10868.
33.
TangY, ChiY, SunJ, et al.Leveraging elastic instabilities for amplified performance: spine-inspired high-speed and high-force soft robots. Sci Adv, 2020; 6:eaaz6912.
34.
KeplingerC, LiT, BaumgartnerR, et al.Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation. Soft Matter, 2012; 8:285–288.
35.
ChenD, YoonJ, ChandraD, et al.Stimuli-responsive buckling mechanics of polymer films. J Polym Sci Part B: Polym Phys, 2014; 52:1441–1461.
36.
RothemundP, AinlaA, BeldingL, et al.A soft, bistable valve for autonomous control of soft actuators. Sci Robot, 2018; 3:eaar7986.
HongS, LeeH, LeeJ, et al.Highly stretchable and transparent metal nanowire heater for wearable electronics applications. Adv Mater, 2015; 27:4744–4751.
39.
ChoiS, ParkJ, HyunW, et al.Stretchable heater using ligand-exchanged silver nanowire nanocomposite for wearable articular thermotherapy. ACS Nano, 2015; 9:6626–6633.
40.
LiJ, LiangJ, JianX, et al.A flexible and transparent thin film heater based on a silver nanowire/heat-resistant polymer composite. Macromol Mater Eng, 2014; 299:1403–1409.
41.
GeJ, YaoH, WangX, et al.Stretchable conductors based on silver nanowires: improved performance through a binary network design. Angew Chem Int Ed, 2013; 52:1654–1659.
SongL, MyersAC, AdamsJJ, et al.Stretchable and reversibly deformable radio frequency antennas based on silver nanowires. ACS Appl Mater Interfaces, 2014; 6:4248–4253.
44.
YaoS, ZhuY. Wearable multifunctional sensors using printed stretchable conductors made of silver nanowires. Nanoscale, 2014; 6:2345–2352.
45.
CuiZ, HanY, HuangQ, et al.Electrohydrodynamic printing of silver nanowires for flexible and stretchable electronics. Nanoscale, 2018; 10:6806–6811.
46.
HuangQ, ZhuY. Gravure printing of water-based silver nanowire ink on plastic substrate for flexible electronics. Sci Rep, 2018; 8:1–10.
47.
YuanP, McCrackenJ, GrossD, et al.A programmable soft chemo-mechanical actuator exploiting a catalyzed photochemical water-oxidation reaction. Soft Matter, 2017; 13:7312–7317.
48.
ZhaoH, HuR, LiP, et al.Soft bimorph actuator with real-time multiplex motion perception. Nano Energy, 2020; 104926.
49.
LiW, LiF, LiH, et al.Flexible circuits and soft actuators by printing assembly of graphene. ACS Appl Mater Interfaces, 2016; 8:12369–12376.
50.
TaccolaS, GrecoF, SinibaldiE, et al.Toward a new generation of electrically controllable hygromorphic soft actuators. Adv Mater, 2015; 27:1668–1675.
51.
ChangL, HuangM, QiK, et al.Graphene-based bimorph actuators with dual-response and large-deformation by a simple method. Macromol Mater Eng, 2019; 304:1800688.
52.
DengH, ZhangC, SuJ-W, et al.Bioinspired multi-responsive soft actuators controlled by laser tailored graphene structures. J Mater Chem B, 2018; 6:5415–5423.
WuY, YimJK, LiangJ, et al.Insect-scale fast moving and ultrarobust soft robot. Sci Robot, 2019; 4:eaax1594.
55.
OnalCD, RusD. Autonomous undulatory serpentine locomotion utilizing body dynamics of a fluidic soft robot. Bioinspir Biomim, 2013; 8:026003.
56.
TangY, ZhangQ, LinG, et al.Switchable adhesion actuator for amphibious climbing soft robot. Soft Robot, 2018; 5:592–600.
57.
UmedachiT, VikasV, TrimmerBA. Softworms: the design and control of non-pneumatic, 3D-printed, deformable robots. Bioinspir Biomim, 2016; 11:025001.
58.
DudutaM, ClarkeDR, WoodRJ. A high speed soft robot based on dielectric elastomer actuators. In: 2017 IEEE International Conference on Robotics and Automation (ICRA). Manhattan, NY: IEEE, 2017, pp. 4346–4351.
59.
ParkT, ChaY. Soft mobile robot inspired by animal-like running motion. Sci Rep, 2019; 9:1–9.
60.
StuhlmanO. A physical analysis of the opening and closing movements of the lobes of Venus' fly-trap. Bull Torrey Bot, 1948; 75:22–44.
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