Full Paper
www.afm-journal.deJamming Skins that Control System Rigidity from theSurfaceDylan S. Shah, Ellen J. Yang, Michelle C. Yuen, Evelyn C. Huang,
and Rebecca Kramer-Bottiglio*
variable stiffness mechanisms include
stimuli-responsive materials,[7–9] systemlevel antagonistic control,[10–12] and pressure-induced material interlocking or“jamming.”[13,14] In this study, we explore
a new form of material jamming throughadaptive, planar skins that can reversibly
stretch in two dimensions to be sculpted
into complex 3D shapes, and rigidly maintain that shape to serve as tools and exoskeletons for soft objects.
Material jamming uses pressure to control the interaction between disconnected
pieces of inextensible material (either
granular,[15–19] planar,[20] or fibrous[21])enabling a transition between soft andrigid states. For example, in atmosphericconditions, particles such as sand or coffee
easily slide over each other in a fluidlike state, but when pressed together, thegrains pack tightly and resist shear likea solid.[22] Seeking thin variable-stiffness
solutions, researchers have introduced“layer jamming” systems where 2D layersof inextensible material, such as sheets of paper[14] or polyethylene terephthalate (PET),[23] are pressed from a flexible state
into a rigid state by surrounding the sheets in a compliant
membrane and applying a vacuum. Unobtrusive layer jamming
systems have been proven in a variety of applications, including
compliance control of continuum robotic segments,[24,25]
variable-stiffness continuum manipulators,[5,24,25] selectively
compliant grippers,[14,23] and variable-stiffness furniture.[26]However, these jamming approaches either could not stretch,[20]or could only stretch in one direction,[23,27,28] so they are unable
to access complex shapes with compound curvatures, limiting
their versatility.
Achieving 2D stretchability is a strict requirement for creating a universal, shape-locking skin. Gauss’ Theorema Egregium states that inextensible sheets must experience plastic
deformation when bent from their initial flat shape (with uniformly zero Gauss curvature), into more complicated shapeswith nonzero Gauss curvature (e.g., spheres, hyperboloids).[29]In other words, to reversibly adapt to 3D shapes with compound curvatures, a surface needs to be stretchable along two
orthogonal directions. Traditional layer jamming systems, only
able to stretch along one dimension, have exclusively beenable to accommodate curvature about a single axis, practicallylimiting them to shapes such as cylinders or sequences ofNumerous animals adapt their stiffness during natural motions to increase
efficiency or environmental adaptability. For example, octopuses stiffen theirtentacles to increase efficiency during reaching, and several species adjust theirleg stiffness to maintain stability when running across varied terrain. Inspiredby nature, variable-stiffness machines can switch between rigid and soft states.
However, existing variable-stiffness systems are usually purpose-built for aparticular application and lack universal adaptability. Here, reconfigurable
stiffness-changing skins that can stretch and fold to create 3D structures
or attach to the surface of objects to influence their rigidity are presented.
These “jamming skins” employ vacuum-powered jamming of interleaved,
discrete planar elements, enabling 2D stretchability of the skin in its soft
state. Stretching allows jamming skins to be reversibly shaped into loadbearing, functional tools on-demand. Additionally, they can be attached to hoststructures with complex curvatures, such as robot arms and portions of thehuman body, to provide support or create a mold. We also show how multiple
skins can work together to modify the workspace of a continuum robot bycreating instantaneous joints. Jamming skins thus serve as a reconfigurable
approach to creating tools and adapting structural rigidity on-demand.

1. Introduction
Biological organisms leverage a wide range of material properties to adapt to their environments: soft, flexible fish swim
efficiently through water, while the rigid skeletons of large landmammals allow them to support their body weight. Many animals actively control their stiffness to facilitate motion, such as
an elephant grasping with its trunk,[1] octopuses creating virtual
joints during reaching motions,[2] and goats adapting their legs
as they travel over compliant surfaces.[3] Drawing inspirationfrom the versatility of these biological systems,[4] engineers
have designed “variable stiffness” robots and machines,[5,6]which reversibly switch between rigid and soft states, trading
load-bearing capabilities for flexibility. Approaches to creating
D. S. Shah, E. J. Yang, Dr. M. C. Yuen, E. C. Huang,Prof. R. Kramer-Bottiglio
School of Engineering & Applied Science
Yale University
17 Hillhouse Avenue, New Haven, CT 06520, USA
E-mail: rebecca.kramer@yale.edu
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/adfm.202006915.

DOI: 10.1002/adfm.202006915

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www.afm-journal.dediscrete folds. Two notable recent approaches have attempted
to overcome these limitations. First, researchers interleaved
hoops and helices of inextensible material to create sheaths
for bendable continuum arms with constant cross-section.[24,25]
Another proposed approach involves building jammable interfaces from piled stretchable fabrics.[30] While promising, theseprior jamming approaches were tailored to specific applications. For example, the manipulators[24,25] could not be repurposed into jammable interfaces[30] or jamming furniture,[26]and vice versa.
In this work, we introduce thin, reconfigurable “jamming
skins” that can stretch in two dimensions to unobtrusively
accommodate numerous shapes with complex surface curvatures. These jamming skins can be fabricated using a generalizable and scalable manufacturing method to accommodate awide range of design constraints. We show these skins accomplishing a wide range of tasks, including adjusting the trajectory of a soft robot arm to increase its workspace, serving as areconfigurable wrist brace, and building complex structures ondemand (Figure 1). After use in one application, the skins canbe removed and applied to another host body, or be repurposedto create a standalone tool. Their activation mechanism is fastand simple, requiring only application and removal of vacuum
pressure to trigger stiffness change. 2D stretchable jamming
skins have a wide range of applications, from providing unobtrusive physical support for users with joint instabilities, toserving as a reconfigurable tool for use in constrained and/or
resource-limited environments.

2. Results
Jamming skins are composed of a sealed, stretchable membrane containing layers of small overlapping sheets of

intrinsically inextensible material (jamming elements),
linked to prevent de-interleaving of layers (Figure 2A–C).
While at atmospheric pressure, elements can slide overeach other, enabling global stretchability; under vacuum, themembrane presses the elements together and inter-layer friction prevents further sliding, making the skin stiff and inextensible (Movie S1, Supporting Information). A typical skin
could transition from stretchable to fully jammed (-80 kPa)in under 4 s using a vacuum pump. Several design parameters can be adjusted to fit application requirements, if
desired. For example, varying membrane and jamming materials results in different stiffening characteristics when activated,[16,23,27] and increasing the number of layers (n) makes
the skin thicker but improves the stiffening ratio (scaling
with n2,[14] discussed in Suopporting Information). Here, we
specifically demonstrate jamming elements cut into hexagonal shapes from a single sheet of inextensible polyethylene
terapthalate (PET) using a laser cutter, with 2D spring-likeserpentine links[31] connecting each element to enable global
stretchability (Figure 2A,B). The serpentine links prevent the
jamming elements from sliding around inside of a stretchable silicone membrane, ensuring maximum interleaving of
jamming elements throughout multiple stretching and jamming cycles. Additional jamming skins, including a springless design, were manufactured and compared to this main
embodiment (Figures S1 and S2, supporting Information).
However, we found that this main embodiment (hexagonal
elements with springs, as shown in Figure 2) had the highest
stiffness ratio while also being significantly less laborintensive than the springless designs.
Jamming skins can actively change their in-plane (tensile)and out-of plane (bending) stiffness, allowing them to adjust
an enveloped body’s system dynamics from the surface. To
achieve stiffness changes, layer jamming relies on inter-layer

Figure 1. Jamming skins can be applied to the surface of deformable objects to provide support, or be reconfigured to create structures and tools
on-demand. Upon application of a vacuum, the skins transition from flexible and stretchable sheets (no added shading) to stiff surfaces (cyan).
Applications shown in the bottom row, from left to right: continuum manipulator with on-demand joints, reconfigurable table, sculptable reservoir forholding liquids.

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www.afm-journal.deFigure 2. Jamming skins consist of a stretchable membrane and interleaved inextensible elements. A) Top view of a jamming skin. Scale bar is 2.5 cm.
B) PET is laser cut to create numerous jamming elements (here, hexagons) that are centered around regularly spaced nodes (denoted by colored dots).
Elements within a single layer are connected by serpentine springs of PET. Different colors indicate the three unique layer designs which are stacked
and staggered relative to each other. C) Principle of operation, showing the unjammed state (top) and the jammed, inextensible state (bottom). D) Jamming skins have increasing in-plane stiffness at increasing vacuum pressure. The control skin, with homogeneous rectangles of PET, is inextensible andconsistently ripped during testing. Solid lines are representative curves. E) Bending stiffness increases with increasing applied membrane pressure.
(D,E) Shaded regions represent 1 standard deviation, dashed lines represent the mean.

friction to prevent elements from slipping in the presence of
shear stress. Coulomb friction models have been used as firstorder models to design traditional layer jamming systems underboth tensile and bending loading conditions,[14,21,24,25,27,32] andcan be adopted to generate performance predictions and design
goals for our stretchable jamming skins. For example, Coulomb
models predict that the maximum tensile loading force prior toslip F(μ, A, P) is linear for all independent variables, yieldingF∝μ*A*P, where μ is the inter-layer friction coefficient, A is thetotal area of overlap between elements in each cross-section, andP denotes the applied vacuum pressure (derivation presented in
Supporting Information). A similar prediction can be made forthe bending case, as discussed in the Supporting Information.
Thus, for a given jamming skin design, large changes in maximum loading can be quickly attained by increasing the vacuum
pressure. Regardless of loading condition, to maximize jammed
stiffness while minimizing thickness (which also minimizes theunjammed stiffness and the attainable radius of curvature), it isdesirable to maximize the overlap area.
We developed a generalizable procedure to design each layerof PET and attain maximum element overlap, which we applied
to create the hexagonal element patterns shown throughout
this paper. First, we distributed the jamming elements’ centersat nodes defined by the vertices of a simple, patternable baseshape (e.g., a triangle, square or hexagon) tiled throughout

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the jamming area. For our demonstrations, we used a triangular tiling because of its simplicity and dense packing
as shown in Figure 2B. One vertex of each tiled triangle was
assigned to each of three unique layers, and elements in eachlayer were centered at each vertex (node) (shown by the different colored nodes in Figure 2B). This enabled neighboring
elements, situated in different layers, to slide relative to eachother (Figure 2B,C), while maintaining surface-to-surface contact such that they would interlock when the skin was activated.
Once the nodes were assigned to their appropriate layers,
we could uniquely determine the shape and size of each PET
jamming element with the maximum overlap between jamming elements. First, we computed the Delaunay triangulation[33] for each layer design. Then, we connected the Delaunay
nodes to create Voronoi diagrams that evenly divided the space
between nodes, without producing gaps. This resulted in zerowasted material (except for slots required to make the springs)
and maximized jamming element overlap, thereby increasing
the attainable stiffness change. The triangular tiling used inour demonstration generated hexagonal elements, as shown in
Figure 2B. Delaunay triangulations can be efficiently calculated
for arbitrary node distributions,[33] enabling rapid design of
jamming skins that require an irregular node spacing due toother design constraints. Once the design of the three layers
was set, the skins were manufactured by stacking multiple

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www.afm-journal.delayers of each design (n = 12 total layers), and sealing the stackinside a stretchable silicone membrane.
To quantify the performance of the manufactured jamming skins, we measured their mechanical response in tension and bending, while varying the applied vacuum pressure(Figure 2D,E). We also compared the stretchable skins to a control set of identically sized skins containing homogeneous rectangular PET sheets (Figure 2D,E and Figure S3, Supporting
Information), representing traditional layer jamming systems(inextensible layers in flexible membranes[14,20,34]). All of the control skins ripped after stretching more than a few percent strain,
which prevented us from performing any meaningful tensile
tests at any vacuum pressures other than ambient conditions.
In contrast, the jamming skins could repeatedly stretch to ≈20%
strain while unjammed (average stiffness of 0.67 ± 0.05 N m−1
standard deviation), and were relatively inextensible while
jammed at -80 kPa (31.05 ± 4.97 N m−1), resulting in a jamming ratio of 47. As expected, the unjammed force–displacement
behavior was roughly linear throughout the test, because thesilicone membrane and PET springs were being freely stretched.
While jammed, the tensile response was linear at low strains, but
after the tensile load exceeded the maximum friction force andinitiated slip, the skins exhibited an oscillatory stick–slip behavior
at their PET interfaces (Figure 2D, solid lines). By increasing
the pressure from 40 to 80 kPa, the force at slip increased from25.3 ± 5.0 to 38.1 ± 8.5 N, an increase of 51%, confirming thatslip points can be tuned by modulating pressure (Figure S4, Supporting Information). Additionally, we find that pre-slip tensile
stiffness is relatively independent of pressure, as predicted bytheory (Figure 2D and Supporting Information).
In contrast to the tensile loading condition, during bending,jamming skins exhibit multiple slip points rather than a single
slip point (Figure 2E and Supporting Information). This resultsin multi-linear (as opposed to bilinear) curves with numerous
break points that depend on pressure. When coupled with natural inhomogeneities and slight irregularities in surface topo­
graphy during jamming, the force–displacement curves during
bending often exhibited a smoother response. By varying thepressure, users can smoothly tune these slip points and adjust
the perceived stiffness.
Although the jamming skins had a lower bending stiffness
than the control skins in the jammed state, they were significantly more flexible when unjammed (Figure 2E and Figure S4,
Supporting Information). This behavior is primarily a consequence of the stress relief provided by the gaps between elements. As a result, the jamming skins’ mean stiffness ratio
between the jammed and unjammed states (16.6) was higher
than the control skins’ (7.9). In summary, the results presented
here collectively demonstrate that jamming skins can easily
stretch and bend while unjammed, then reversibly switch to an
inextensible and inflexible state.

3. Applications
The universal adaptability enabled by the 2D stretchability ofjamming skins, along with their rapid state switching, makes
them useful in many situations. In this work, we demonstratethem as reconfigurable multitools, load-bearing platforms,
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and contour-matching casts. After acquiring one load-bearing
shape, the skins can be reconfigured into other shapes to serve
different purposes, without requiring modification of the hoststructures or target shapes. The skins’ elasticity and built-in
fabric snaps allow them to stretch around a surface and maintain sufficient contact to provide support.
The simplest form of shape locking can be achieved bymanually bending jamming skins into a desired shape. For
example, a 290 g jamming skin was rolled into a cylinder and,upon activation, the skin stiffened to become load bearing,supporting over 1.5 kg (Figure 3A and Movie S2, Supporting
Information). Additionally, exploiting the watertight silicone
membrane, a skin was formed into a concave shape (nonzero
Gauss curvature) and used as a temporary liquid-holding vessel(Figure 1 and Movie S5, Supporting Information). The same
skin was reconfigured into numerous other functional shapes
including a shovel, a shelter for delicate objects, a book stand,a ramp for robots to ascend, a cup for holding water, stiffening
for a manipulator made using robotic skins,[35] and a tool holder(Movie S3 and Figure S5, Supporting Information).
To demonstrate complex 3D contour matching, we placed ajamming skin on top of a variety of objects on a vacuum table.
Engaging the vacuum table pulled the skin inward toward theobject, prompting the skin to locally stretch and conform to theobject’s contours. We used this procedure to make the jamming
skin match the shape of numerous objects with complex curvatures, including a 3D-printed model of a face, an artificial pieceof fruit, and a tape measure (Figure 3B and Movie S4, supporting Information). In particular, the face had a wide range ofGauss curvatures ranging from zero (along the chin) to positive(forehead), to negative (eye sockets), all of which the jamming
skin replicated and retained in its final shape. Due to the orderof-magnitude stiffness change experienced by the skins during
jamming, the resulting casts could sustain significant externalload, as shown in Figure 3B. Since rigidity is proportional toboth modulus E and moment of area I, forming the skins into
3D shapes increases the load-bearing capacity relative to the flat
configuration (Supporting Information). Thus, by achieving 2D
stretchability, jamming skins can reconfigure into complex 3D
shapes and gain architectural strength.
We attempted to recreate the shape-locking and structural
support capabilities presented here using the control skins(Figure S6, Supporting Information). While the control skins
could indeed support loads in several of their jammed configurations, a few deficiencies predicted by the Theorema
Egregium and throughout this manuscript were confirmed.
The control skins resisted stretching even in their unjammed
state, making reconfiguration difficult and making it nearly
impossible to accommodate surfaces with nonzero Gauss
curvatures. Each control skin ripped after only a few reconfigurations, preventing their long-term usability as a reconfigurable multitool. In order to approximate surfaces with
nonzero Gauss curvatures, the control skins had to be foldedand creased. This caused permanent plastic deformationof the jamming elements, making them hold their shapeeven after the vacuum was removed. In contrast, all of thejamming skins used in this manuscript underwent dozens
of uses, and have yet to fail during normal use (i.e., without
being punctured or over-stretched).

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www.afm-journal.deFigure 3. Jamming skins can be reconfigured to form load-bearing 3D shapes or to lend rigidity to soft structures. A) A jamming skin rolled into arigid cylinder. B) Left column: A single jamming skin matching the shape of a 3D printed face, a banana, and a tape measure. Right column: the skinlocked into the same shapes, supporting weights. C) Supporting a user’s wrist. D) Locking a foam tube into a bent shape. All scale bars are 5 cm.

When stretched around the surface of objects, jamming
skins provide support analogous to an exoskeleton: the rigidityof the relatively thin layer prevents the softer underlying structure from further deforming (Figure 3C,D). For example, thejamming skin provided joint support which could be useful forrehabilitation purposes (Figure 3C and Movie S5, Supporting
Information). While unjammed, the skin bends with the user’s
motion. By varying the pressure, the skin’s rigidity could be
adjusted to apply varying levels of resistance, or even immobilization of the encased joint. The same jamming skin wasapplied to a foam tube where it stretched and compressed withthe tube, then maintained deformed shapes (Figure 3D andMovie S6, Supporting Information). This jamming skin was
also used to create joints on-demand in a continuum manipulator (Figure 4), showing the reconfigurability and versatility of
an individual skin.
During reaching motions, octopuses generate virtual joints
in their tentacles, allowing them to dexterously grab theirtarget.[2] Seeking to emulate this virtual-joint technique, weapplied jamming skins to a robotic continuum arm, creating
joints on-demand that enabled dynamic adjustment of theoperating workspace (Figure 4A). We applied three jamming
skins in series along a foam cylinder, overlapping each other byapproximately 1 cm. The manipulator was actuated by a stringthat was tied to an eyelet at the end, routed through the base,and pulled a fixed distance by a mechanical testing machine.
Through selective jamming of each skin, we sampled eachof the eight possible combinations and obtained representative deformation curves and attainable trajectories. Bending
tended to occur at new joints that appeared near the interfaces
between two skins (Figure 4B). The eight permutations roughly
clustered into four sets, denoted by the four colors in Figure 4.
Relative to the reach attained when all skins were unjammed,
the manipulator could adjust its trajectory to achieve tighter

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reaches (33% closer to the starting position), as well as wider
reaches (27% farther), with the same actuator stroke. Thus, byusing the jamming skins to create new joints, a skin-manipulator system could attain multiple workspaces without the needfor multiple actuators.
The skins’ modularity allows continuum manipulators tobe quickly modified, not only in terms of workspace as shown
above, but also their materials, design, and construction. To
meet the design requirements of a given application, the coreof the manipulator could be swapped for another material withdifferent properties. Extra joints could be added by re-configuring or adding jamming skins, new tasks could be completed
by adding end-effector tools, or a different actuator could be
used (e.g., replace the cable with pneumatic actuators,[36] shapememory alloys[37] or other soft actuators[38]), all without having
to re-design the skins.

4. Outlook
This study presents a method for creating thin, elastic skins
with controllable in-plane stretchability, and thus, 3D rigidity.
By generating space-filling designs that allow interleaved
layers of inextensible material to accommodate 2D strains,
jamming skins can be flexed and stretched to take on a wide
range of 3D forms. Example applications demonstrated in thispaper include: reconfigurable load-bearing structures, shapematching casts, tools that can be quickly re-shaped and repurposed, human joint support, and on-demand joints for acontinuum manipulator.
However, there are a few fundamental limitations which canbe addressed through further hardware optimization. During
strain, we observed that some of the serpentine springs would
snag on neighboring elements and become fully extended

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www.afm-journal.deFigure 4. Multiple jamming skins applied to a continuum manipulator to create joints on-demand. A) Depending on the jamming state, the manipulator would bend at a different location, resulting in different end-effector trajectories. Illustrations next to each final end-effector location denote thejamming status of each skin. B) Final configurations. Scale bar is 5 cm. Skins with cyan shading were jammed at a vacuum of ≈85 kPa, while unshadedskins were at atmospheric pressure.

prior to attaining the global strain limit. When this occurred,
the springs would pull their connected jamming elements outof the alternating layering pattern, reducing inter-layer friction
and weakening the jamming effect. Additionally, neighboring
elements on an outermost layer (top, bottom) would occasionally stick to the enclosing membrane, causing a stress concentration and tearing the membrane near their shared edge.
To counteract these problems, we simply tuned the springgeometry (longer and narrower springs), and increased themembrane thickness. Each of these solutions comes with a
trade-off: longer and narrower springs have less restorative
force to return the skins to their initial state, and thicker membranes increase the skins’ unjammed stiffness. However, wefound that the achieved strain range still enabled our skins toattain a wide range of practical shapes. We suspect that future
design optimization and introduction of inextensible materials
with higher fracture strains (allowing the springs to stretch
farther) will allow the skins to accommodate larger changes inlocal strain with fewer undesired side-effects.
With higher-fidelity models, jamming skins could bedesigned to optimally target a set of applications and tasks,
while satisfying specific design constraints. At a first approximation, jamming skins can be analyzed using extensions of
traditional layer jamming modeling techniques, as discussed
in this manuscript. However, the skins’ inhomogeneous properties limit the accuracy of predictions generated using suchmodels. While this does not hinder the use of jamming skins
in general-purpose applications, it does pose a challenge fordesigning precise systems that need accurate performance
predictions a priori. Additionally, it is unclear how to predict
the smallest attainable radius of curvature (κmin) as a functionof the skin design. Solving this theoretical problem is important for accurate modeling, since κmin determines the level ofdetail that jamming skins are able to reproduce when reconfigured or formed to an object. Prior work suggests κmin is on theAdv. Funct. Mater. 2021, 31, 2006915

same order as the skin thickness,[29] but determining a rigorous
model for the minimum bending radius is still an unsolved
problem. This type of model will enable design of future jamming skins that optimally balance competing design outcomes,
including attainable change in stiffness, shape resolution(i.e., range of attainable shapes), thickness, and maximum
strain. Additional inclusion of active, switchable adhesives on
the outer membrane could further facilitate shape locking ofcomplex topographies.
The new form of layer jamming presented herein opens up
possibilities for designing reconfigurable tools and robots. The
hardware is relatively inexpensive, and the skins are quick toactivate and reconfigure. We believe that this work will lead toadvanced rehabilitative garments and assistive smart clothing,and enable individuals, such as astronauts, to create tools andstructures in resource-limited environments. Combined withrecent advances in shape-changing robots,[39] sensory skins,[40]stretchable circuits,[41,42] and 3D shape sensing sheets,[43] weenvision future robots where the shape and (exo)skeleton ofa robot are not fixed, but rather dynamically adaptable to therobot’s environment and goals.

5. Experimental Section
Manufacturing: The jamming skins used in this study comprises
a silicone membrane (Dragon Skin 10, Smooth-On), and layers of
0.1 mm thick PET that were laser cut (LPKF ProtoLaser U4) to make thejamming elements. Fiber-reinforced silicone[44] was used to connect themembrane seal to the jamming area. For the tension and bending tests,
the dimensions of the active jamming area was 130 mm by 45 mm, thewidth chosen such that two jamming elements could fit side-by-side.
Two larger skins based off of this jamming skin design were used forthe application-oriented experiments: the 12-layer square membrane(Figures 3A,C,D and Figure 4) had an active jamming area of 130 mm
by 130 mm and the larger 20-layer rectangular skin (Figure 3B) had ajamming area of 226 mm by 307 mm (limited by the size of the LPKF

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www.afm-journal.deProtolaser U4 used). To provide comparison with prior art, a control
set of skins with rectangular (130 × 45 mm) 0.1 mm thick PET in asilicone membrane was also manufactured and tested under tension
and bending. Additional designs, mechanical characterization, andmanufacturing schematics are presented in the Supporting Information.
Mechanical Characterization Test Procedure: Three specimens of eachjamming skin design (designs include the one presented in Figure 2, thecontrol set, and three others discussed in the Supporting Information)
were tested on a materials testing machine (Instron 3345) five times
each under tension and bending at three pressures (0, 40, and 80 kPa).
The tests were performed under quasi-static conditions at 15 mm min−1
for tension and 10 mm min−1 for bending. Additional details and results
regarding characterization are presented in the Supporting Information.
Informed signed consent was obtained from the authors that tested thejamming skins in wearable applications, to both participate in the study
and to publish any identifiable images.
Manipulator: For the manipulator experiment, a single string was
pulled by a mechanical testing machine (Instron 3345) at 300 mm min−1
until 200 mm under eight jamming conditions, corresponding to all
possible permutations of active and inactive states for the three appliedskins. To keep the motion in-plane for simplicity, Teflon was adhered
to the bottom of the system and the manipulator rested on a fabricbackground. To stabilize the base, an acrylic cylinder was inserted into
the foam tube such that approximately 2 cm of the skin closest to thebase overlapped the acrylic. Video was captured from directly above
the manipulator, and the manipulator tip was tracked by extracting
the centroid of a piece of red tape placed on the end effector, using
MATLAB’s computer vision toolbox.

Supporting Information
Supporting Information is available from the Wiley Online Library orfrom the author.

Acknowledgements
This work was supported by an NSF Emerging Frontiers in Researchand Innovation grant (1830870) and by NASA through the Early Career
Faculty Program (grant numbers NNX14AO52G and 80NSSC17K0553).
DSS was supported by a NASA Space Technology Research Fellowship(Grant 80NSSC17K0164). EJY was supported by a NASA Connecticut
Space Consortium grant (Grant NNX15AI12H). The authors would liketo thank Liana Tilton and Hannah Steele for help with photography and
Dr. R. Adam Bilodeau for help with the manuscript text.

Conflict of Interest
The authors declare no conflict of interest.

Author Contributions
D.S.S. and R.K.-B. conceived the idea. D.S.S., E.J.Y., and E.C.H. designed
and built the hardware. D.S.S., M.C.Y., E.J.Y., and E.C.H. designed andperformed the experiments. D.S.S., M.C.Y., and R.K.-B. analyzed theresults. All authors contributed to, and agree with, the content of the
final version of the manuscript.

Data Availability
The data that support the findings of this study are available from thecorresponding author upon reasonable request.

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Keywords
laminar jamming, reconfigurable structures, shape locking, soft robotics
Received: August 15, 2020
Revised: September 8, 2020
Published online: September 24, 2020

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