HydraFlex™ (In Development)
An in-development hydraulic artificial muscle system targeting high-pressure operation
What is a hydraulic artificial muscle?
A classic McKibben-style artificial muscle is:
A flexible inner bladder
Wrapped in a braided sleeve
Terminated with end fittings
Pressurized to generate an axial pulling force
For HydraFlex, the pressure medium is hydraulic fluid instead of air.
That means:
Higher stiffness (less compressibility)
Higher force potential for a given diameter
More plumbing discipline
Why hydraulics are interesting
Higher force density
Hydraulics let you run at much higher pressures than typical pneumatic setups, which can translate to higher force in the same form factor.
Better controllability (sometimes)
Lower compressibility can make pressure control feel less like herding cats.
Portable power, still decoupled
Like pneumatics, you can keep the heavy parts off-joint:
Pump
Reservoir
Accumulator (optional)
Valves and filtration
Then route lightweight hoses to the muscles.
HydraFlex vs AeroFlex
HydraFlex and AeroFlex muscles are mechanically very similar.
What stays the same:
Bladder + braid + end fittings architecture
Contraction physics (geometry-driven)
Mounting patterns and modular “muscle as a part” philosophy
What changes:
Operating pressure target is much higher
Material requirements get brutal (bladder + braid + termination)
The “system” shifts from compressor/regulator to pump/reservoir/valves
If you have not read the AeroFlex overview yet, start there.
AeroFlex™ (In Development)Design targets (R&D)
These are targets for the R&D program, not promises. If you are looking for guaranteed specs, HydraFlex is not ready to date.
Operating pressure
500 psi (≈ 3.45 MPa)
High force in compact form
System footprint
Compact pump + plumbing
On-board or wearable-friendly
Muscle form factor
Modular sizes
Repeatable, swappable builds
Characterization
Force/pressure/length curves
Control loops need data
Failure behavior
Predictable + documented
No mystery bursts
What we are building (behind the curtain)
HydraFlex is not just a muscle. It is a muscle ecosystem.
Right now this looks like bench rigs, off-the-shelf plumbing, and a lot of material coupons that live short, exciting lives.
1) High-pressure braided muscles
Core R&D focus:
Bladder material that survives pressure, flexing, and cycling
Braided sleeving that holds geometry without shredding the bladder
End fittings that do not turn into weak links
2) A compact hydraulic pump pack
We are starting with off-the-shelf components:
Pumps
Fittings
Hoses
Valves
Then we shrink and standardize once the requirements are real.
3) A sane integration story
The endgame is modular building blocks:
Standard muscle sizes
Standard fluid interfaces
Mounting hardware that is not “whatever was in the drawer”
What we are actively researching and improving
Muscle materials at 500 psi
The muscle is the hard part.
We are testing combinations of:
Bladder materials and wall thicknesses
Braids (Carbon Fiber vs aramid-class fibers, different picks and weaves)
Termination methods (clamps, ferrules, overmolds, hybrid approaches)
End fittings and terminations
A high-pressure muscle fails at the interface first.
We care about:
Leak rate under static pressure
Leak rate under bending and cycling
Repeatable assembly without “artisan torque”
Small, tight hydraulics
A compact pump system needs:
Pressure relief (mandatory)
Filtration and fluid cleanliness
A layout that is serviceable
Sensing and control
HydraFlex wants to behave like a real actuator, not “adjust pressure until it looks right.”
Planned focus areas:
Pressure sensing close to the muscle
Force sensing in-line or at the joint
Control modes: pressure, force, and position
Where HydraFlex is headed
You will see this section grow as we move from lab prototypes to something you can actually build with.
Our roadmap is roughly:
Prove a repeatable 500 psi muscle build
Publish force/pressure/length characterization
Package a compact pump/valve module
Release reference designs (joints, limbs, and wearables)
Who this is for (today)
HydraFlex is for you if:
You want high force density without rigid gear trains
You are building at “body scale” (wearables, limbs, animatronics)
You have the lab discipline to work with pressurized fluid
You are collaborating with us on R&D (or you are intentionally reading ahead)
If your plan involves zip ties as primary safety hardware, start with AeroFlex.
Further reading
Hydraulic McKibben muscles have a deep research history. Here are some solid starting points:
Last updated
Was this helpful?