3D Printed Miniature Walking Robot with Soft Joints and Links

Utilization Ranging from Military Surveillance to Search and Rescue in Disaster Areas

At a Glance

A multimaterial 3D printing (MM3P) was leveraged to fabricate centimeter-scale robots by utilizing soft materials to create joints and links. A three-spring rotational-prismatic rotational (RPR) model is developed to approximate the motion of soft joints or links and to numerically predict the motion of the leg mechanism. The accuracy of the proposed numerical method is validated with experimental results. A functional walking robot actuated by a single DC motor has been demonstrated. Using MM3P, both rigid and soft materials can be printed, and this method saves time, as the robot is fabricated as a whole and does not need assembling. 


Miniature robots have many applications ranging from military surveillance to search and rescue in disaster areas. Nevertheless, the fabrication of such robots has traditionally been labor-intensive and time-consuming.

Researchers at Colorado State University proposed the concept of both soft joints and links for mechanisms and demonstrate the concept with a functional walking robot prototype fabricated using MM3P. MM3P allows for 3D printing both soft and rigid materials and allows the entire robot to be printed at once, eliminating the need for fabrication of separate parts and assembly. This can save time and money, both during development and testing, and manufacturing.

Mechanisms with soft or compliant joints have been investigated in the field of compliant mechanisms and used in various miniature robots (e.g., flying and walking). Mechanisms with compliant links have also been studied before in the context of large-scale robotic manipulators. 

However, mechanisms with both soft joints and links will significantly improve the life cycle of compliant mechanisms as the flexibility of soft links can reduce the force exerted on soft joints. Therefore, such mechanisms will be more robust and reliable for a wide range of applications including robotics, deployable structures, or mechanical metamaterials. Also they developed a numerical method to predict the motion of mechanisms with soft joints and links. Most of the existing work either only investigated a single soft joint or relied on complicated kinetostatic models to analyze mechanisms with compliant elements. The CSU researchers’ numerical method can serve as a basis for more general and in-depth theoretical investigations (e.g., dynamics) for mechanisms with soft elements. 


Compared to existing fabrication methods, directly using MM3P has two distinctive advantages:

(1) Fabrication process is without human intervention, and thus easier and faster. In fact, with appropriate designs, multi‑material 3D printers can directly print both soft and rigid materials in a single part.

(2) A variety of materials can be chosen for different performance requirements. For example, there exist seven soft materials with different tensile strength for PolyJet printing. As a result, 3D printed soft joints or links can have different characteristics depending on design requirements.


  • Military surveillance
  • Search for survivors in disaster areas
  • Mobile sensor networks for dynamic environmental monitoring
Last Updated: May 2023
3D Printed Miniature Walking Robot with Soft Joints and Links

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Jianguo Zhao
Anthony Demario

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Aly Hoeher