🛰️Robotic Arm-assisted Additive Manufacturing of Liquid Metal Embedded Materials

Space University Research Initiative (AFOSR / AFRL)

PI: Prof. Carmel Majidi

Carnegie Mellon University – Soft Machines Lab

Pittsburgh ,PA

Oct 2023 – May 2025

UR5e robotic manipulator with custom syringe extruder printing on a calibrated substrate. The RA3M setup synchronizes arm trajectory and extrusion for conformal deposition across planar, vertical, and inverted surfaces.

🎯 Objectives

Integrate a 6-DOF UR5e with a modular syringe extruder and ROS control for synchronized motion-extrusion.
Enable multi-orientation printing (planar, vertical, inverted, sloped) with consistent filament width and layer stacking.
Formulate & qualify a stretchable DAI-CNT-LM composite ink suitable for electrical/thermal functionality.
Demonstrate functional parts—multilayer Joule heaters and heat-sink geometries—with stable interlayer adhesion.
Characterize performance (rheology, mechanical, electrical, thermal) and define operating windows for reliable prints.
Identify next steps toward closed-loop standoff/surface tracking for fully adaptive conformal deposition.

💡Motivation

Additive manufacturing in space and extreme environments faces unique challenges—such as variable gravity, limited support structures, and material constraints. Conventional 3D printers are confined to planar surfaces and rigid materials, restricting their use in complex, curved geometries.

This project was motivated by the need for a robotic platform capable of conformal, multi-axis printing of soft, conductive materials to fabricate stretchable electronics, heaters, and thermal components directly on irregular surfaces—enabling autonomous in-space manufacturing and on-demand material deposition without supports.

⚙️ Approach

Iterative design of the modular syringe extruder integrated with the UR5e arm.

Extruder Design

Designed a custom modular syringe extruder to dispense high-viscosity conductive inks with precision.
Progressed through three design iterations (V1–V3) to improve modularity, mass distribution, and stability on the UR5e wrist.
V1: Commercial Hyrel metal head – high mass and limited syringe capacity.
V2: Redesigned open-source FRESH pump – reduced length by 42 mm and supported multiple syringe types.
V3: Lightweight 3D-printed frame with smooth-shaft linear guides and high-torque NEMA-17 motor, achieving 21 % weight reduction and enhanced orientation control.
Supports 1–10 mL Luer-lock or Hamilton syringes, enabling fast material swaps and precise extrusion on vertical/inverted surfaces.

Formulation workflow of the DAI-CNT-LM conductive composite ink

Ink Development

Formulated a DAI-CNT-LM composite ink combining fluoroelastomer (Daikin G801EL), carbon nanotubes (CNTs), and eutectic gallium–indium (EGaIn) to achieve simultaneous electrical, thermal, and mechanical functionality.
Developed a multi-stage dispersion and planetary mixing process ensuring uniform CNT distribution and strong CNT–LM interfacial bonding.
Achieved shear-thinning rheology and low tan δ (< 1) — enabling controlled extrusion and stable deposition on vertical and inverted surfaces.
Measured 200 % strain-at-break and 370 kPa Young’s modulus, confirming high elasticity and structural integrity under deformation.
Verified conductivity up to 56 S/m, with resistance stability maintained under 200 % cyclic strain, suitable for stretchable heaters and interconnects.
Optimized ink performance for multi-layer stacking and rapid post-deposition solidification, critical for conformal robotic printing.

System Integration

Workflow overview of the RA3M system. The pipeline includes ink formulation and material characterization, extruder and robotic calibration, and trajectory-controlled deposition using the UR5e robotic arm.

Trajectory generation and controller overview

📊 Key Findings

Developed a ROS–Python controlled 6-DOF UR5e robotic platform enabling synchronized motion and extrusion for conformal additive manufacturing on planar, vertical, and inverted surfaces.
Engineered a lightweight modular syringe extruder achieving 21 % mass reduction and precise volumetric dispensing for high-viscosity inks.
Formulated a stretchable DAI-CNT-LM composite ink (200 % strain-at-break, 56 S/m conductivity) suitable for robotic printing of flexible heaters and heat sinks.
Demonstrated support-free multi-layer builds (up to 20 layers ≈ 10 mm) with stable inter-layer adhesion and verified rapid thermal response (< 20 s) via FLIR imaging.

Printing UV curable polymer.mp4

Printing high aspect ratio structures.mp4

vertical, inverted, cup.mp4

Printing NFC antenna and eigen bot.mp4

Rover repair task.mp4

SIS LM AG ink.mp4

FKM ink video_2.mp4

FKM ink video.mp4

Poster.pdf

Poster presented at the Graduate Research Symposium, Department of Mechanical Engineering, Carnegie Mellon University, 2025 — Space University Research Initiative (SURI): Robotic Arm-Assisted Additive Manufacturing of Liquid Metal Composites.

View the Graduate Thesis Here

Final Report.pdf

🌍 Impact

The RA3M system establishes a robust platform for conformal, support-free additive manufacturing on complex 3D surfaces. By integrating liquid-metal composite inks, UR5e robotic motion planning, and real-time extrusion control, it enables precise, multi-layer deposition with high conductivity and structural fidelity. This work advances the frontier of functional material printing for applications in soft electronics, thermal management, and in-space manufacturing.

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