Soft Bot concepts

Peripatus on a leaf

Link to DSO site and notes

Current Draft


  • Why start large and go small? Why not start small and stay small?
    • As Zakin clarifies, they really want soft and deformable
    • Greater speed when larger
    • Better able to cope with environment at small length scales (holes/crevices in ground)
    • Larger workspace for locomotion or manipulation of payload
    • Snakes (which can go through small holes, have a respectable payload and can travel rapidly and even climb, cannot manipulate...
  • Compelling reasons to use H202?
    • Relatively high energy density
    • No sealed hydraulic or pneumatic cylinders
    • Flexible fuel tank as part of the "novel soft payload"
    • Inherently suited to soft robot - no need for transmission, motor, etc.
  • Payloads
    • Fuel for chemical actuation
    • Battery for electronics and non-chem actuation
    • Actuation hardware (valves, motors, SMA, etc.)
    • Electronics/control
    • Camera or other hardware
    • Other?
  • Locomotion
    • Phase I milestone is .25 m/minute or 4mm/sec, which is REALLY SLOW
    • Probably allowing for novel chemical morphing locomotion schemes.
    • A 10cm inchworm or caterpillar can move significantly faster than that
    • Which is why Onycophorans will probably be an OK model
  • Actuation Types
    • Mark Yim and Polybot style - probably not what they want, but would be feasible for task, if not scale
    • SMA - slow, but they're ok with slow. Also very low energy efficiency (about 2%)
    • EPAM - possible... could work with with octopus or amoeba structure to squeeze radially, producing axial extension
  • Variable stiffness chassis?
    • Lots of discussion in BAA about rheological fluids, modulus-changing, phase transitions, etc.
    • We have worked with ER and MR fluids in the past. They could provide advantages for structures that lock up when the fluid is energized but become very deformable when it is not.
    • Perhaps they're focused on a normally stiff robot that can "melt" when necessary, more than a flexible robot that can change locomotion methods?
    • A cartoony character (Scooby Doo, perhaps) came to mind... walking on tiptoes normally, and then switching to being prone with sprawled legs, but still moving on tiptoes

Soft robot literature

Denis Hong at Virginia Tech. has an amoeba robot concept:

Bio Links and Background Information

Velvet Worms (Onycophorans)

Berkeley site:

Other sites:

Velvet Worms date back 400 millions years and may be a missing link between the Arthropods (Insects and Crustaceans) and Annelids (soft bodied segmented worms, including earthworms).

Although wormlike appearance and having a segmented body, the Peripatus have legs which move in similar fashion to the eyes of a snail and are able to be extended by variations in internal blood pressure.

Shy creatures, able to hide in incredible tight crevices, these “velvet worms” are rarely seen in their natural habitat but could be found in leaf litter, earthen tunnels and foliage, under stones, and in fallen trunks.

Bunch of good pictures on this site + a quote:

The largest are only about 20 centimeters in length.

Their pliable and soft integument have earned them the name of "velvet worms". Indeed, an onycophore is so flexible that it is able to "filter" (there is no better word to describe it) through incredibly narrow spaces.

Scutigera coleoptrata

House centipede. Fast predator that is able to hide under rocks & etc. This is the other end of the spectrum of designs we could consider, with distinct legs, high running speed.


Sea Stars (starfish)and other Echinodermata

Class: Asteroidea, Phylum: Echinodermata

These creatures use a water vascular system for propulsion and for applying (large) forces to open mussel shells. Other potentially relevant echinodermata include sea cucumbers (Holothuroidea), which have lost much of their skeleton

They have remarkable powers of regeneration.

Echinodermata have an endoskeleton consisting of many ossicles, which could be roughly analogous to the small discrete components that our robots will have.

"The connective tissue is mutable and its consistency is under nervous control."

This might be something one could do with ER fluid in a spongey matrix...

Lab on "movement by fluids" --

sea cucumber

At regular intervals along the radial canal lateral canals branch off and conduct canal fluid to a fluid reservoir, the ampulla, which surmounts each tube foot. Ampullar muscles encircle this reservoir. When the ampullar muscles contract they displace fluid into the podium. The walls of the tube foot are encircled spirally by connective tissue. This tissue resists any tendency for an increase in the girth of the podium; instead the tube foot protracts, becoming longer and reaching farther away from the body. There is a tiny one-way valve in the lateral canal of each tube foot which prevents back flow during ampullar muscle contraction. If this were not so the (incompressible) fluid would leak out to the radial canal. %ENDCOMMENT%

Polychaeta (annelid worms) -- these creatures have been the subject of some robotics work at SSSA in Pisa. They have an excellent ability to traverse sandy terrain, navigating between rocks.


Another possible model for a soft bot that can morph between an "expanded" and an "extruded" state:

Fiber-Wound Animals

Elastic Mechanisms in Animal Movement -R. McNeil Alexander; 1988. -- Good section on the effects of inextensible fibers in animals: Chapter 5, "Fibre-wound Animals"

Compliant Actuators and Refs

Valves and materials

Various groups have worked on compliant actuators over the years. A group at Ritsumeikan University in Japan, in particular, has worked on various 'soft robot' technologies. And of course there is also Octor...

Concept Drawings


Solidworks Files

Deflated with background
Inflated with background
Cross Section
Foot Detail


Powerpoint File of drawings

Powerpoint File of more drawings


  • Requirements: 3/8 inch OD, Wall thickness - 0.015", 20-30 Shore-A, H2O2? compatible
  • Difficult to mold into thin wall tube (Source: Dow Corning Tech help)

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