2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)
April 4-8, 2022, Edinburgh, UK

An Electromagnetic Soft Robot that Carries its Own Magnet

2022 IEEE 5th International Conference on Soft Robotics (RoboSoft) | 978-1-6654-0828-8/22/$31.00 ©2022 IEEE | DOI: 10.1109/ROBOSOFT54090.2022.9762196

William R. Johnson III1 , Stephanie J. Woodman1 , and Rebecca Kramer-Bottiglio1

Abstract— Existing magnetically actuated soft robots require
an external magnetic field to generate motion, limiting themto carefully controlled laboratory settings. Here, we introduce
an electromagnetically actuated soft robot that can locomote
without an external magnetic field. The robot is designed tocarry its own magnet, which it alternately retracts and repels.
Friction-biased feet transform this back-and-forth linear motion
into forward locomotion, mimicking an earthworm gait. We
demonstrate a characteristic velocity of 1.5 body lengths per
second (31.3 mm/s) and actuation speeds over 150 Hz. This
work paves the way for fully autonomous, untethered magnetic
soft robots.

I. I NTRODUCTION
Fig. 1. An example locomotion trial. The robot achieves locomotion byrepeatedly attracting and repelling an on-board permanent magnet. Scalebars: 1 cm.

Soft robotics is a burgeoning field motivated by thelimitations of traditional, rigid robots and inspired by theelasticity of biological tissues. The natural compliance ofsoft robots makes them attractive for applications where they
have close contact with humans and safety is a priority, including biomedical [1] and assembly line applications, while
their robust ability to absorb unpredictable impacts makes
them attractive for deployment to remote and unstructured
terrains [2], [3]. These advantages motivate researchers todevelop soft alternatives to components of traditional robots,
including computation [4], sensing [5], and actuation. Softactuators often rely on active material responses to stimuli
such as heat [6]–[9], light [10], pressure [4], [7], [11], andmagnetic fields [1], [10], [12], [13]. This work focuses on
advancing the state of the art of electromagnetically actuatedsoft robots beyond current limitations.

soft electromagnetic actuator made of liquid metal channels
encapsulated in silicone [12]. These actuators could generatea magnetic field when current was sourced, so the robot
body could align itself with an external field. The authors
showcased a swimming fish as well as a ping-pong playing
soft robot, both of which could actuate with applied current
in the presence of a strong, external magnet. Novelino
et al. introduced magnetic-responsive origami robots thatexhibited distributed control of a robotic arm when placedin an apparatus that could modulate the magnetic field in
two Cartesian directions [13]. Hu et al. designed a robot
made from silicone elastomer and magnetic microparticles
for multimodal locomotion [14]. By controlling the external
magnetic field, they demonstrated the robot walking, rolling,crawling, jumping, swimming, and even transitioning fromland to water and vice versa.

A. Environment Dependence of Magnetic Soft Robots
Electromagnetically actuated soft robots typically rely on
an external magnetic field for actuation and control. We
refer to robots in this class as environment dependent since
they cannot operate in the absence of this magnetic field.
There is a large body of work on environment-dependent
electromagnetic soft robots. Yang et al. presented a glutenbased ferromagnetic spray that can be coated or patterned
onto soft bodies [1]. The spray acts as a magnetic “skin,”allowing the substrate to become a soft robot actuated by
an external magnetic field. The authors demonstrated theconcept with origami robots that could walk in the presenceof a pulsing magnetic field and a capsule robot that could besteered through a rabbit’s stomach by a modulated magnetic
field for targeted drug delivery. Mao et al. demonstrated a

B. Environment Independence
Outside of environments where magnetic fields can be
carefully controlled, soft robots need to exhibit environment
independence so that they can control themselves without relying on external magnetic fields. Few examples ofenvironment-independent electromagnetic soft robots can befound in the literature. Kohls et al. created an electromagnetic actuator using compliant permanent magnets andsilicone tubing filled with liquid metal [15]. When a current
is applied, the magnets are attracted to the center of thecoil, achieving actuation that mimics a Xenia coral. The
authors further developed this actuation strategy to design asoft gripper that can grasp and hold pieces of paper [16].
Guo et al. designed a robot jellyfish, a robotic fishtail,and a gripper with soft, liquid metal coils and on-board
permanent magnets [17]. Because these robots contain their

WRJ is supported by the National Science Foundation (NSF) under grantno. IIS-1955225. SJW is supported by the NSF under grant no. EFMA1830870
1 Department of Mechanical Engineering and Materials Science, Yale
University, New Haven, CT, USA will.johnson@yale.edu

978-1-6654-0828-8/22/$31.00 ©2022 IEEE

761

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.

Fig. 3. Diagram of the fluidic circuit designed to mitigate the effects ofelectromigration. The tubes filled with liquid metal (LM) that make up theelectromagnetic coil extend to two metal plugs to which wire leads wereattached. LM was injected using a syringe until the tubes were filled, andthen the tubes were capped with the metal plugs. A check valve was used
to prevent back flow into the syringe.

Fig. 2. Illustration of the actuation mechanism. The liquid metal coilalternately attracts and repels the magnetic foot. One cycle of these two
motions is a step, and multiple steps with friction biased feet invoke forward
locomotion.

Electromigration is the transport of mass in metals subjected
to high currents [20], and it has frequently caused open
circuits especially when high currents are applied to liquid
metals [21].

own permanent magnets rather than rely on external magnetic
fields, they are environment independent. Kohls’s robotic
gripper, however, is heavy and is demonstrated only as an end
effector. Similarly, Guo’s robots are not capable of locomotion. Nemitz et al. presented Wormbot, a locomoting robot
actuated with on-board electromagnetic voice coils [18].
While Wormbot exhibits environment independence, it contains many rigid components, including 3D printed partsand rigid circuit boards, and the only soft component isthe elastomeric body segment in between each voice coil.
Wang et al. demonstrated a high-speed electromagnet robot
with environment independence [19] where the only rigid
components were the coil and the permanent magnet. Herein,
we present a soft, electromagnetic robot that carries its own
magnet (Figure 1). Our robot advances the state of the art byachieving environment-independent locomotion with a soft
electromagnetic coil.

A. Magnetic Field Strength
The magnetic field B in the center of a solenoid is given
by equation 1 where µ0 is the magnetic permeability of freespace, I is the current through the liquid metal coils, N is
the number of turns, and l is the overall length of the device.
µ0 IN
(1)
l
The practical considerations for our design are current
and weight. Since the magnetic field strength is directly
proportional to current, higher currents yield stronger actuation forces. However, electronics cannot source infinite
current, making current a limiting factor when designing therobot. Compensating for current limitations by increasing thenumber of turns comes with a weight trade-off since eGaIn is
the heaviest component of the robot (see Table I for the mass
bill of the robot). Coil density N/l is limited both by weight
and the dimensions of the tubing. In practice, locomotion
was best with a stronger magnetic field and a lighter robot.
To accommodate these constraints, the thinnest available
tubing (1/32” ID) was used to maximize the coil density
and minimize the overall length of the robot—reducing its
weight without affecting the magnetic field. The final lengthof the coil was chosen to be 1 cm.
B=

II. D ESIGN AND FABRICATION
To demonstrate environment-independent locomotion, we
designed an earthworm robot inspired by work from Rothemund et al. [4] with electromagnetic actuators in place ofpneumatic actuators. Back-and-forth linear motion is generated by repeatedly attracting and repelling a permanent
magnet using a soft electromagnetic coil (Figure 2) madefrom eutectic gallium-indium (eGaIn), a room-temperatureliquid metal. The 2 cm long robot has friction-biased silicone
feet that transform this back-and-forth linear motion into
forward locomotion (Figure 1). Designing this soft robot
required us to solve two main challenges. First, we needed
to generate a magnetic force strong enough to overcome
internal friction in order for the robot to move. Second, we
needed to mitigate the problem of electromigration failure.

B. Electromigration
Electromigration is a phenomenon that occurs when ahigh current is applied to a conductive material. If thecurrent density is sufficiently high, atoms are broken off
the structure and physically moved, creating areas of vacancies that can lead to open circuits [20]. Though this762

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.

Fig. 4. The robot is manufactured in two halves, the magnetic foot and the liquid metal coil. In the first manufacturing step, two silicone feet are cast in
3D printed molds. To make the magnetic foot, a permanent magnet and a piece of string are overmolded with a cylinder of silicone on one of the silicone
feet. To make the liquid metal coil, silicone tube is wrapped around a rod wrapped in Teflon and coated with silicone. This coil is then adhered to thesecond silicone foot, and a hole is cut in the end. The two halves are assembled by pulling the magnetic foot’s string through the hole in the liquid metal
coil’s foot and tying a knot at the end.

a small amount of additinal eGaIn into the circuit via thecheck valve.

occurs with all metals, the fluid state of liquid metals
makes them especially susceptible [21]. When our robot was
initially designed, it would only take a few steps before
an electromigration failure caused an open circuit, stopping
the robot where it stood. Existing strategies for mitigating
electromigration failure did not suffice for our robot. Kent etal. addressed electromigration experimentally by measuring
the mean time to failure for different currents through theircircuits and avoiding high currents that they knew would
cause failure [21]. Unfortunately, currents low enough to
avoid electromigration failure do not generate enough force
to overcome friction and make our robot move. Kohls et
al. included liquid metal reservoirs at both ends of theircircuit [16] perhaps to address failures they experienced due
to electromigration, though they explain their strategy as one
that accommodates thermal expansion and prevents oxide
formation. Including reservoirs at either end of our coil did
not work for us in practice (see Section III-A).

C. Fabrication Process
The fabrication process for our robot is detailed in Figure 4. We refer to the half of the robot which holds thepermanent magnet as the magnetic foot. The magnetic foot ismade of silicone elastomers (DragonSkin 30 and DragonSkin
10; Smooth-On), a 1/4” × 1/4” cylindrical magnet, and ashort length of string to enforce the step length. First, the footis cast by pouring DragonSkin 30 into a 3D printed polylactic
acid (PLA) mold and allowing the silicone to cure. The footis 15 mm in diameter and has a slight bias at the bottom
like the earthworm robot in [4]. A small length of string is
attached to the bottom tip of the foot with a silicone adhesive(Sil-Poxy; Smooth-On) to reduce the friction between thefoot and the substrate. Then, the magnet is placed in thecenter of the foot and overmolded with silicone (DragonSkin
10 Fast; Smooth-On) using another PLA mold. The end of
the string is knotted and inserted into the elastomer after
it is poured so that the magnetic foot is fabricated with aprotruding string. The protruding boss where the magnet isembedded is wrapped in 1/2” Teflon tape and sprayed withethanol to minimize friction as it slides along the inside of
the coil during actuation.
The liquid metal coil makes up the larger half of therobot’s body, consisting of coiled tubing adhered to a silicone
foot similar to the one described above. To create the coiled
tubing, Teflon film is wrapped around a 10 mm rod to createa low-friction interface, and a length of 10 mm is marked
on the film. Then, 1/32” ID low-durometer, flexible silicone

Our approach to mitigate electromigration is a fluidic
circuit we designed to make our liquid metal coils a closed
system (Figure 3). A syringe is used to inject eGaIn into thecircuit via a one-way valve. Then, metal plugs (1/32” barbed
to 1/8” NPT connectors filled with eGaIn and followed by
1/8” NPT plugs) are used to close the ends of the tubes aswell as interface with the electrical leads that provide power.
Closing the system mitigates electromigration because the
eGaIn has no room to escape. This fluidic circuit allowed
us to complete hours of locomotion trials without electromigration failure. After sustained use, electromigration stillcaused eGaIn to leak out of our metal plugs and create open
circuits, but the robots were repaired instantly by injecting
763

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.

tubing (5236K203; McMaster-Carr) is wrapped seven times
around the rod and encapsulated with silicone (DragonSkin
10 Very Fast; Smooth-On). After 20 minutes of curing, thecoils are slid off the rod and glued to the foot using silicone(DragonSkin 10 Very Fast; Smooth-On). A hole is cut inthe middle of the foot for the string to pass through. The
magnetic foot is inserted into the coils to form the earthworm
robot. The string embedded in the magnetic foot is pulled
through the hole in the coil’s foot and knotted such that the
robot’s maximum extension is limited by the knot at 6 mm.
The tubing is then injected with eGaIn using a syringe via thefluidic circuit we discussed in Section II-B. Table I details
the major components in terms of mass on each half of therobot, which has a total mass of 7.5 g.
TABLE IM ASS B ILL
Magnetic Footmagnetsilicone footLiquid Metal CoileGaIn
silicone coilsilicone footFig. 5. Magnetic force output as a function of current for a LM coil witha copper coil as a control. Both coils exert the same force on the magnet
for a given current. The magnetic force output varies linearly with the input
current. Markers represent the mean and error bars represent the standard
deviation of five trials.

3.0 g
1.5 g
1.1 g
4.5 g
1.9 g
1.3 g
1.1 g

fluidic circuit is the only solution that made locomotion trials
possible, and even when electromigration failures do occur,
the fluidic circuit allows coils to be easily healed by injecting
more eGaIn throught the one-way valve.

III. E XPERIMENTAL M ETHODSTABLE IIWe characterize the system’s robustness to electromigration, force output, and actuation frequency. Robustness toelectromigration is compared to Kohls’s solution of reservoirs [16] as well as simply inserting copper leads at either
end of the coil. Magnetic force output is compared to a control robot that was the same size and shape but constructedwith thin (32 AWG) copper wire inside the silicone tubing
instead of eGaIn. We present locomotion trials conducted
at different actuation frequencies where the robot achieves
a speed of 1.5 body lengths per second. Finally, turning isdemonstrated by attaching two robots together and actuatingthem at different frequencies.

C OMPARISON OF E LECTROMIGRATION S OLUTIONSTime toFailureSample 1
Sample 2
Sample 3
Sample 4
Sample 5

Electromigration Solutions
Fluidic Circuit
Reservoirs
Wire Leads
6 h 26 mina
1 min 24 s
2 min 2 s
1 min 34 s
2 min 42 s
1 min 0 s
53 min 44 s
7s
1 min 17 s
7 h 45 minb
3 min 49 s
1 min 38 s
16 h 50 minb,c7s
1 min 39 s

Mean
6 h 23 min
1 min 38 s
Median6 h 26 min
1 min 24 s
a Paused overnight at 5 h 5 min.
b Paused overnight at 7 h 43 min.
c Never failed.

A. Preventing Electromigration
We confirmed the efficacy of the fluidic circuit strategy
described in Section II-B by comparing it experimentally to
two other potential solutions to electromigration failure. For
this experiment, 15 liquid metal coils were manufactured:
five with the fluidic circuit, five with eGaIn reservoirs ateither end like those mentioned in [16], and five withcopper wire leads. Each sample was energized with 5 A ofcontinuous current until an open circuit failure occurred. The
time to failure for each sample is shown in Table II. Our
fluidic circuit is the only solution that survived more than a
few minutes of exposure to 5 A of current, lasting for morethan 6 hours on average. As indicated in the table, several
samples fabricated with the fluidic circuit had to be paused
overnight—after handling many hours of high current—andthen resumed the next day. One sample did not fail evenafter two days, at which point the test was stopped. The

1 min 31 s
1 min 38 s

B. Magnetic Blocking ForceThe robot’s coil was placed in a materials testing system(Instron 3345) to characterize the magnetic force it is capableof generating. A 1/4” neodymium magnet (the same magnet
that we embed into the robot) was attached to the Instron’s
crosshead, which we lowered down until the whole magnet
was just inside the coil, the same location where it would be
for the forward stroke of its locomotion gait. The coil wasenergized with different currents, and the resulting force on
the magnet was measured. The experiment was repeated witha control robot that was the same size but with copper wire
inside the silicone tubing instead of eGaIn. The experiments
show a linear dependence of magnetic force on appliedcurrent and no difference in force output between the liquid764

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.

[a]

[b]

Fig. 7. A turning robot was created by adhering two robots together.
Applying differential step delays to the actuators resulted in a turning gait.
For the pictured trial, the top actuator had a step delay of 3 ms while thebottom actuator had a step delay of 25 ms.

and the metal plugs together have an electrical resistance of
0.6 Ω, so a potential difference of 3 V is required to energize
the coil with 5 A of current. The control signal for the gait isa square wave parameterized by a step delay indicating how
long the robot pauses before switching steps (Figure 6a).
To find the optimal step delay for high-speed locomotion,
we recorded the robot walking and varied the step delay
between trials. The robot’s speed was measured by tracking
the recorded videos using a video analysis software (Tracker;
physlets.org), and the results are plotted in Figure 6b. The
highest speed of 31.3 mm/s was recorded for a step delayof 25 ms, corresponding to more than 1.5 body lengths
per second for our 2 cm robot. The speed decreases withincreasing step delay due to slower steps. Below 25 ms, therobot does not have enough time to take full steps before
the direction of the current is switched, resulting in slower
speeds.
The locomotion trials were conducted on an acrylic substrate lubricated with ethanol to reduce friction between
the silicone feet and the substrate. In addition to friction,
the robot’s tether to the power supply plays a significant
role in inhibiting locomotion. For this reason, the speed extracted from each video was the maximum constant velocity
achieved throughout a trial.

Fig. 6. [a] The robot is controlled by a square wave paramaterized bydifferent step delays. Step delays of 10 ms and 100 ms are shown forreference. [b] The effect of step delay on speed when the robot was actuatedat 5 A. A step delay of 25 ms generated the highest speeds, reaching
31.3 mm/s (1.5 body lengths per second). Longer step delays result in slower
walking because the robot pauses between steps. Step delays smaller than
25 ms also result in slower speeds because the actuation is too fast for the
robot to take full steps.

metal coil and the copper control (Figure 5), a result thatis congruent with Equation 1. At 5 A of current, the robot
exerts a 45 mN force on its magnetic foot.
C. Forward Locomotion
Friction-biased feet allow the robot to transform its backand-forth linear motion into forward locomotion. The robot’s
gait comprises a forward stroke where the coil repels themagnet to push the robot’s front foot forward and a backstroke where the coil attracts the magnet and pulls the backfoot forward. The robot is controlled with a high-power
motor driver (Pololu G2 18v25), which switches the directionof current through the coil in order to proceed from theforward stroke to the backstroke and repeat. The eGaIn coil

D. Turning
To achieve turning gaits, two robots were attached together
using a silicone adhesive (Sil-Poxy; Smooth-On). The turning strategy for this robot is to actuate one side with the
optimal step delay of 25 ms and actuate the other side at ahigh frequency so that it vibrates and reduces static friction(Figure 7). To observe the turning gait and other locomotion
trials, the reader is directed to the accompanying video.
765

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.

IV. C ONCLUSION[14] W. Hu, G. Z. Lum, M. Mastrangeli, and M. Sitti, “Small-scale softbodied robot with multimodal locomotion,” Nature, vol. 554, no. 7690,
pp. 81–85, 2018.
[15] N. Kohls, B. Dias, Y. Mensah, B. P. Ruddy, and Y. C. Mazumdar,“Compliant electromagnetic actuator architecture for soft robotics,”
in 2020 IEEE International Conference on Robotics and Automation(ICRA). IEEE, 2020, pp. 9042–9049.
[16] N. Kohls, I. Abdeally, B. P. Ruddy, and Y. C. Mazumdar, “Design of a
xenia coral robot using a high-stroke compliant linear electromagnetic
actuator,” ASME Letters in Dynamic Systems and Control, vol. 1, no. 3,
p. 031011, 2021.
[17] R. Guo, L. Sheng, H. Gong, and J. Liu, “Liquid metal spiral coilenabled soft electromagnetic actuator,” Science China Technological
Sciences, vol. 61, no. 4, pp. 516–521, 2018.
[18] M. P. Nemitz, P. Mihaylov, T. W. Barraclough, D. Ross, and A. A.
Stokes, “Using voice coils to actuate modular soft robots: wormbot,
an example,” Soft robotics, vol. 3, no. 4, pp. 198–204, 2016.
[19] Q. Wang, X. Lu, N. Yuan, and J. Ding, “Small-scale soft robot withhigh speed and load capacity inspired by kangaroo hopping,” AdvancedIntelligent Systems, vol. 4, no. 1, p. 2100129, 2022.
[20] J. R. Black, “Electromigration—A Brief Survey and Some Recent
Results,” IEEE Transactions on Electron Devices, vol. 16, no. 4, pp.
338–347, 1969.
[21] T. A. Kent, M. J. Ford, E. J. Markvicka, and C. Majidi, “Soft actuators
using liquid crystal elastomers with encapsulated liquid metal jouleheaters,” Multifunctional Materials, vol. 3, no. 2, p. 025003, 2020.

This paper presents the first electromagnetic soft robotthat carries its own magnet. We have demonstrated thatelectromagnetically actuated soft robots can operate withenvironment independence—without the need for controlling external magnetic fields—even for complex tasks like
locomotion and even while avoiding rigid metal coils andother rigid components. This is a critical step toward making
electromagnetism a viable actuation strategy for future soft
robots that we envision operating in authentic environments
and closely interacting with humans.
We also presented an innovative and straightforward solution to electromigration, representing a path forward forhigh-current applications with liquid metals where electromigration is a common failure mode. Future work will involve
incorporating a soft permanent magnet to make the robot
completely soft and untethering the system so that it canalso carry its own controller and power supply.
R EFERENCES[1] X. Yang, W. Shang, H. Lu, Y. Liu, L. Yang, R. Tan, X. Wu, andY. Shen, “An agglutinate magnetic spray transforms inanimate objects
into millirobots for biomedical applications,” Science robotics, vol. 5,
no. 48, p. eabc8191, 2020.
[2] M. T. Tolley, R. F. Shepherd, K. C. Galloway, R. J. Wood, G. M.
Whitesides et al., “A resilient, untethered soft robot,” Soft robotics,
2014.
[3] A. P. Sabelhaus, J. Bruce, K. Caluwaerts, P. Manovi, R. F. Firoozi,
S. Dobi, A. M. Agogino, and V. SunSpiral, “System design andlocomotion of superball, an untethered tensegrity robot,” in 2015 IEEE
international conference on robotics and automation (ICRA). IEEE,
2015, pp. 2867–2873.
[4] P. Rothemund, A. Ainla, L. Belding, D. J. Preston, S. Kurihara, Z. Suo,and G. M. Whitesides, “A soft, bistable valve for autonomous controlof soft actuators,” Science Robotics, vol. 3, no. 16, 2018.
[5] J. Shintake, E. Piskarev, S. H. Jeong, and D. Floreano, “Ultrastretchable strain sensors using carbon black-filled elastomer composites andcomparison of capacitive versus resistive sensors,” Advanced Materials
Technologies, vol. 3, no. 3, p. 1700284, 2018.
[6] T. L. Buckner, R. A. Bilodeau, S. Y. Kim, and R. Kramer-Bottiglio,“Roboticizing fabric by integrating functional fibers,” Proceedings of
the National Academy of Sciences, vol. 117, no. 41, pp. 25 360–25 369,
2020.
[7] J. W. Booth, D. Shah, J. C. Case, E. L. White, M. C. Yuen, O. CyrChoiniere, and R. Kramer-Bottiglio, “Omniskins: Robotic skins thatturn inanimate objects into multifunctional robots,” Science Robotics,
vol. 3, no. 22, 2018.
[8] K. Liu, F. Hacker, and C. Daraio, “Robotic surfaces with reversible,
spatiotemporal control for shape morphing and object manipulation,”
Science Robotics, vol. 6, no. 53, pp. Art–No, 2021.
[9] C. S. Haines, M. D. Lima, N. Li, G. M. Spinks, J. Foroughi, J. D.
Madden, S. H. Kim, S. Fang, M. J. De Andrade, F. Göktepe et al.,“Artificial muscles from fishing line and sewing thread,” science, vol.
343, no. 6173, pp. 868–872, 2014.
[10] C. Li, G. C. Lau, H. Yuan, A. Aggarwal, V. L. Dominguez, S. Liu,
H. Sai, L. C. Palmer, N. A. Sather, T. J. Pearson et al., “Fast andprogrammable locomotion of hydrogel-metal hybrids under light andmagnetic fields,” Science Robotics, vol. 5, no. 49, p. eabb9822, 2020.
[11] J. W. Booth, O. Cyr-Choiniere, J. C. Case, D. Shah, M. C. Yuen, and
R. Kramer-Bottiglio, “Surface actuation and sensing of a tensegrity
structure using robotic skins,” Soft Robotics, 2020.
[12] G. Mao, M. Drack, M. Karami-Mosammam, D. Wirthl, T. Stockinger,
R. Schwödiauer, and M. Kaltenbrunner, “Soft electromagnetic actuators,” Science advances, vol. 6, no. 26, p. eabc0251, 2020.
[13] L. S. Novelino, Q. Ze, S. Wu, G. H. Paulino, and R. Zhao, “Untethered
control of functional origami microrobots with distributed actuation,”
Proceedings of the National Academy of Sciences, vol. 117, no. 39,
pp. 24 096–24 101, 2020.

766

Authorized licensed use limited to: Yale University. Downloaded on July 25,2022 at 14:12:37 UTC from IEEE Xplore. Restrictions apply.