NASA Technical Reports Server (NTRS) 20130009430: Fibrillar Adhesive for Climbing Robots

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by  NASA Technical Reports Server (NTRS)

Materials & Coatings
Transformers: Shape-Changing Space Systems Built With
Robotic Textiles
These easy-to-fabricate textiles can be used in robotics and smart habitats/shelters.
NASA’s Jet Propulsion Laboratory, Pasadena, California
Prior approaches to transformer-like Second, the ro-textile layer is fold- the circuits of all subsystems (electron-
robots had only very limited success. able to small volume and self-unfolding ics/computing, propulsion, and power
They suffer from lack of reliability, abil- to adapt shape and function to mission photo-elements/imaging cells, actuators,
ity to integrate large surfaces, and very phases. Tightly folded at launch, it conductors for antennas, etc.).
modest change in overall shape. Robots would self-unfold to take the A cell-based architecture fits well with
can now be built from two-dimensional shape/function needed by the mission modular, reconfigurable electronics,
(2D) layers of robotic fabric. This ex- target, and then again transform its based on field programmable (FP) ar-
pands on ideas of electronic fabrics for shape as needed. For dramatic rays, or in general on distributed com-
electronic textiles, and incorporates sen- changes, one can speculate it could puting/electronics. From computa-
sors, actuators, power, and communica- morph between a large solar sail for in- tional perspective, each (cm-size) cell of
tions. The 2D solution is easier/cheaper terplanetary interstellar travel, its com- the ro-textile could be a basic computa-
to fabricate, packs more compactly, and ponent patches could separate in tional element — a single FPGA (field
ensures a wider range of shape change swarms of winged flyers in atmosphere, programmable gate array)/FPAA (FP
than 3D modules. or it could take shape as a limbed robot gate/analog array) mixed cell, a cluster
These transformers, a new kind of ro- capable of surface mobility and sample of cells, or a large-density array of FP
botic space system, are dramatically dif- manipulation. cells (the low density may be suitable for
ferent from current systems in at least Some 3D payloads may still be needed, non-silicon materials that may be
two ways. First, the entire transformer is e.g., some special instruments that can- preferable for reasons other than high
built from a single, thin sheet; a flexible not be integrated as 2D structures; these integration). The ro-textile would be
layer of a robotic fabric (ro-fabric); or would be carried as payloads in kernels built with materials that survive to ex-
robotic textile (ro-textile). The ro-textile around which the 2D layer would fold. treme environments without insulation
would be produced as a gossamer-thin Proper partitioning of the ro-fabric sheet or thermal control.
(≈100 µm) and light flexible layer, sur- would allow shaping of practically any 3D In summary, this concept may be a so-
vivable to extreme environments. Along shape, as insured by various mathemati- lution to faster, cheaper, and lighter
its large surface, the ro-fabric would be cal proofs. Flexible layers would provide space systems, reducing the launch cost
partitioned into modular cells. Each cell further freedom for modification of and the redesign cost for new missions;
would include, distributed within this shape at sub-cell resolution. thus, one can launch more of them and
skin-like thin layer, all the structures for The surface of ro-fabrics is composed at shorter intervals, and send them to
spacecraft/robotic subsystems, includ- of connected (zipped) multi-cell patches more places after launch.
ing propulsion and power (solar), avion- that can separate to operate in forma- This work was done by Adrian Stoica of
ics and controls, sensing, actuation (e.g., tions; these may be all the same or spe- Caltech for NASA’s Jet Propulsion Laboratory.
shape- memory alloys), and communica- cialized (e.g., one with more sensing cir- Further information is contained in a TSP
tion (circuits and antennas). cuitry). Each cell would normally embed (see page 1).NPO-48349
Fibrillar Adhesive for Climbing Robots
This material can be used to hang items on walls without the need for drilling holes, as surgical
sutures, or to attach and maneuver components during assembly.
NASA’s Jet Propulsion Laboratory, Pasadena, California
A climbing robot needs to use its ad- Common failure modes include tearing, The material consists of a hierarchical
hesive patches over and over again as it contamination by dirt, plastic deforma- fibrillar structure that currently contains
scales a slope. Replacing the adhesive at tion of fibers, and damage from load- two levels, but may be extended to three
each step is generally impractical. If the ing/unloading. A gecko-like fibrillar ad- or four levels in continuing work. The
adhesive or attachment mechanism can- hesive has been developed that has been contacting level has tens of thousands of
not be used repeatedly, then the robot shown useful for climbing robots, and microscopic fibers made from a rubber-
must carry an extra load of this adhesive may later prove useful for grasping, an- like material that bend over and create
to apply a fresh layer with each move. choring, and medical applications. intimate contact with a surface to
NASA Tech Briefs, January 2013 9
achieve maximum van der Waals forces. veloped at JPL to make this process sim- of the wedge leaning to the same side,
By maximizing the real area of contact pler, more reliable, and to allow new i.e., an actual overhang of the fibers,
that these fibers make and minimizing geometries not previously possible. which is more like the arrangement of a
the bending energy necessary to achieve These new geometries will make the ad- gecko foot’s fibers. A third critical differ-
that contact, the net amount of adhe- hesive and the reliability significantly ence is the use of a standard positive No-
sion has been improved dramatically. better, and will drive down cost and de- valac photoresist, which has a wide
The suspension structure consists of velopment time. process latitude.
millimeter-scale fibers that are bonded to The process involves using optical li- The new microfabrication process has
the contacting level through a wet assem- thography to make a master pattern, allowed the shape of the wedge-like
bly step. These millimeter-sized fibers and from this master pattern, making a fibers to be controlled. Prior to these
serve as a discretized way of both con- reusable master mold that is used to cast process improvements, only right-angle
forming to roughness on the surface and the adhesive strips. To create the master wedges had been fabricated. Now, the
distributing the overall climbing loads photoresist pattern that will be used to process not only allows for increased
down to the individual contacts. These make the master mold, a self-aligned control over the angle of these fibers,
structures have been tested on an experi- double exposure technique was used. but is also much more reliable, manufac-
mental testbed meant to determine the Two different angled UV exposures are turable, and cost-effective.
contact forces very exactly, and have also performed using a single opaque pat- This work was done by Aaron Parness and
been demonstrated by hanging weights tern on a transparent wafer. This simpli- Victor E. White of Caltech for NASA’s Jet
off of a patch adhering to a variety of walls fies fabrication considerably. Propulsion Laboratory. Further information
(glass, metal, wood, plastic, drywall, etc). A second advantage of this technique is contained in a TSP (see page 1). NPO-
This material is fabricated via a mold- is the ability to achieve right-angle 48156
ing process. A new process has been de- wedge-shaped structures with both sides
Using Pre-Melted Phase Change Material to Keep Payloads in
Space Warm for Hours Without Power
Goddard Space Flight Center, Greenbelt, Maryland
Adding phase change material from the radiator(s) to space. For the which is about 225 kJ/kg, and a range of
(PCM) to a mission payload can main- interplanetary Probe, PCM is melted by melting points. For example, C18H38 has
tain its temperature above the cold sur- heaters just prior to separation from a melting point of 28 °C, which is well
vival limit, without power, for several the orbiter when power is available within the payload temperature limits.
hours in space. For the International from the orbiter power system. After At the time of this reporting, paraffin
Space Station, PCM is melted by heaters the Probe separates from the orbiter, wax PCM had a TRL (technology readi-
just prior to the payload translation to the PCM releases its latent heat to make ness level) of 7.
the worksite when power is available. up the heat loss from the Probe exte- This work was done by Michael Choi of God-
When power is cut off during the six- rior to space. dard Space Flight Center. FFurther information
hour translation, the PCM releases its Paraffin wax is a good PCM candidate. is contained in a TSP (see page 1). GSC-
latent heat to make up the heat loss It has a high solid-to-liquid enthalpy, 16539-1
10 NASA Tech Briefs, January 2013