Charlot Lab · Physical AI × Material Science × Additive Manufacturing

The Printable
Actuator.

A readiness map for building a humanoid entirely by additive manufacturing — every actuator subsystem, what AM can do today with hard numbers, and the one wall it can't cross.

CC0 1.0 — public domain Free Humanoid Corpus rev 2026.07 subsystem × process × demonstrated performance × TRL × source
00

Two additive regimes

Everything in additive manufacturing for robots splits into two worlds. A fully-printed humanoid lives in the gap between them — which is why no one has built one.

Regime A

Rigid · electromagnetic

Metal AM. Every subsystem — cores, windings, magnets, flexures — is individually demonstrated at high performance.

Proven in isolation · never integrated · silicon is the wall

the
gap
unclaimed
Regime B

Soft · fluidic

Polymer AM. The entire robot already prints in one shot — including its control logic as printed fluidic transistors.

Whole robot, one print · low force · small scale
01

The subsystem matrix

Each actuator subsystem, the AM processes that reach it, the best result demonstrated to date, and an honest technology-readiness estimate. TRL is shown as a nine-layer deposition stack.

Ready · TRL 6–9 · print it now Frontier · TRL 3–5 · demonstrated, not fielded Wall · TRL 1–2 · physics blocks it
Subsystem
AM process
Best demonstrated
Readiness
Ceiling / what's unsolved
Src
02

Actuation topologies

The standard radial BLDC is optimized for machining and winding, not printing. These are the print-native alternatives — ranked by how much of each one AM can actually make.

03

The one wall

Drive — power stage + controller

You cannot print a power MOSFET, GaN, or SiC die, or an MCU. These require crystalline-semiconductor fabrication; printed and organic thin-film transistors cannot switch motor-level power. Printed electronics reaches the board, interconnect, passives, and even PCB-trace encoders — but not the active power and logic silicon. This is the only subsystem AM genuinely can't cross. There are two ways through it.

Escape A — fab it yourself

Trade "printed" for "ours." A self-fabricated open die (SKY130 / GF-class) is a coherent — arguably stronger — sovereignty claim than pretending a printed transistor can drive 40 A. The lab already fabricates silicon.

Escape B — leave the electronic domain

Printed fluidic logic already controls whole actuated robots end to end — diodes and pressure-gain "transistors" printed in a single run. Zero silicon, at the cost of speed and power density.

04

The white space

In the rigid regime, every piece is proven but:

  1. no one has integrated the subsystems into a single printed actuator;
  2. no one has printed it in one or few processes instead of six separate ones;
  3. no one has closed the loop without bought silicon.

In the soft regime, the whole robot prints in one shot but can't carry a biped's loads.

The track's thesis is the bridge: rigid-regime force density, soft-regime one-print integration, and printed-or-self-fabbed control — accounted in joules per joint, released CC0 as prior art.

05

Who's building this

Four capabilities, four separate research communities. No group occupies the intersection — multi-material AM + morphology/control co-design + print-native actuation at humanoid load. The nearest institutional analog is a wind-turbine program.

Make the body

Multi-material AM · computational fabrication
MIT CSAIL / Distributed Robotics · Daniela RusPrintable hydraulics — co-prints solid + liquid into a complete actuated robot; voxel/viscoelastic materials.
MIT Computational Design & Fab · Wojciech MatusikVoxel / digital-materials printing and structure-plus-controller co-optimization. Spans ① and ②.
Harvard Wyss / Lewis Lab · Jennifer LewisMultinozzle MM3D, voxelated matter, functional / structural / biological inks.
ETH Complex Materials · André StudartMultimaterial soft actuators with programmable bioinspired architectures.
MIT Center for Bits & Atoms · Neil GershenfeldThe heterodox path: discrete lattice assembly — reversible, reconfigurable digital materials.

Design body + brain together

Morphology–control co-design
Columbia Creative Machines · Hod LipsonScalable co-optimization of morphology and control; pioneered electronics / bio / food 3D printing.
Univ. Vermont · Josh BongardEvolutionary co-design; xenobots.
EPFL CREATE Lab · Josie HughesGraph-grammar co-design of morphology + control; reconfigurable bistable joints — built, not just simulated.
Northwestern · CMU · Pathak et al.Universal controllers that accelerate co-design past retrain-per-body.

Print the actuator itself

AM of electric machines — closest to the problem
NREL + ORNL + NASA Glenn — MADE3DMultimaterial AM of every motor component + topology/shape co-design toolsets. Your problem, solved for wind generators. The clearest reference & transfer target.
ORNL Manufacturing Demo Facility · Love / PostBAAM, isotropic bonded NdFeB, printed soft magnets, multi-metal LPBF.
Fraunhofer (IFAM / ILT / IWU)Cast coils toward 90% fill; ceramic-insulated copper — cracks the winding-insulation gap.
Nottingham Centre for AMPrinted Fe-Si SRM rotors; AM electrical machines.
IndustryAdditive Drives (printed coils) · Maxxwell (rare-earth-free axial-flux) · Aerosint (multi-metal LPBF).

Print-native actuation

Soft & artificial muscle
Max Planck IS, Stuttgart · Christoph KeplingerHASEL electrohydraulic artificial muscles; Robotic Materials department.
Cornell Organic Robotics · Rob ShepherdRapid 3D printing of electrohydraulic actuators; tough printable silicones; embodied energy.
Yale Faboratory · Rebecca Kramer-BottiglioSoft robots, printable skins, variable stiffness, robots-that-make-robots.
CMU · ETH · UCSD · Harvard · BristolMajidi (liquid metal) · Katzschmann (electrohydraulic + ORCA) · Tolley · Wood/Bertoldi (PneuNets) · Rossiter/Lepora (EAP + tactile).
06

The machine stack & build order

No single machine spans structural polymer + soft-magnetic steel + copper + magnet + elastomer. It's a process portfolio. Here is the optimal process per subsystem, the frontier that consolidates them, and the sequence to build.

Process family
What it makes best
Representative machines / services
The consolidation — and the moat

The minimum viable stack is three machine classes: (1) polymer powder — MJF or SLS — for structure, gears and flexures; (2) multi-material metal LPBF for the electromagnetic actuator; (3) material-jetting or direct-ink-write for soft actuators and sensors. Metal LPBF is the capability-defining, expensive one.

The single machine that collapses the actuator core: Aerosint's selective powder deposition prints 316L steel + CuCrZr copper in one LPBF build — exactly the soft-magnetic-core-plus-winding pairing a motor needs. No platform yet spans metal + polymer + functional inks in a single system. Owning that convergence is the manufacturing-research frontier — and the moat.

Build order

07

Sources

[1]Berkeley Humanoid Lite — arXiv:2504.17249 (UC Berkeley, 2025). Sub-$5k printed & walking humanoid.
[2]ToddlerBot — arXiv:2502.00893 (Stanford, 2025). Fully 3D-printed, independently reproduced.
[3]OpenQDD (A. Musa) & MIT Mini-Cheetah QDD (B. Katz) — open printed cycloidal actuators.
[4]Mohammadi et al., metamaterial flexure joint — Int. J. Bioprinting 9(3), 2023.
[5]Riede et al., AISI 316L flexure-pivot bearings by AM — Materials 12, 2019.
[6]LPBF Fe-5%Si SRM rotor, tested vs. laminated — Univ. Nottingham.
[7]Binder-jet + sinter Fe-6Si soft magnets, 99% dense / 1.83 T — US Pat. 11,993,834.
[8]AM of soft/hard magnetic materials — state-of-art review, ScienceDirect 2022; NREL/ORNL MADE3D program.
[9]High-performance Cu-LPBF winding — 79% slot-fill @ 87% IACS.
[10]Additive Drives 3D-printed copper coils (65% fill, +45% output); ExOne × Maxxwell Motors binder-jet windings.
[11]ORNL big-area additive manufacturing of bonded NdFeB magnets.
[12]3D-printed piezoceramic, d33 583 pC/N; printed PVDF-TrFE piezo sensors.
[13]MIT CSAIL "Printable Hydraulics" — MacCurdy, Katzschmann, Kim, Rus, arXiv:1512.03744.
[14]Edinburgh Soft Systems — electronics-free printed walker, pneumatic ring oscillator, arXiv:2502.10547.
[15]Fully 3D-printed soft robots with integrated fluidic circuitry — Science Advances, abe5257.
[16]Aerosint selective powder deposition — multi-metal LPBF, 316L + CuCrZr in a single build (Aconity MIDI+ / Schaeffler).
[17]MADE3D final technical report — multimaterial AM of every electric-machine component + co-design toolsets (NREL/ORNL/NASA Glenn).
[18]Cheney, Bongard, SunSpiral, Lipson — scalable co-optimization of morphology and control in embodied machines.
[19]EPFL CREATE Lab (J. Hughes) graph-grammar co-design; Cornell ORL (R. Shepherd) & Max Planck (C. Keplinger) — 3D-printed electrohydraulic (HASEL) actuators.