Close-up of two small black wheels attached to silver metal legs on a plain light background.

Hyundai Research Project

Shock Absorption Wheel for Walker / 2025 / 1 semester

Project Overview

Inspired by the Sea urchin’s ball-and-socket joint, I redesigned a standard 5-inch walker wheel using elastic sphere modules to create alternating soft and rigid zones. Through iterative CAD modeling and additive manufacturing in TPU and PAHT-CF, I refined the structure for improved strength and demonstrated enhanced performance at low indoor thresholds.

Tools

3D Printing
Prototyping
Biomimicry
Rhino

Materials

MDF Wood
PHAT-CF(PA12+Carbon Fiber)
TPU

Motivation

Having grown up with my grandmother, I became aware of how standard walkers fail at small thresholds, forcing users to lift the device and lose support. This project reimagines the walker wheel as an adaptive system that maintains stability while crossing everyday obstacles.

Rethinking the Wheel-Ground Interface

Close-up of a walker’s wheel getting stuck over a wooden floor with a small gap between the floorboards near a gray rug.

Mobility begins at the wheel — the primary interface between the human body and the ground.
Most walker wheels rely on rigid, solid tires, offering limited shock absorption over small indoor thresholds and uneven surfaces. This project explores how biological joint systems manage flexibility and stiffness simultaneously and translates those principles into an adaptive wheel architecture.

Inspiration

Sea Urchin
Ball and Socket
Mechanics

Sea urchin spines are attached to the shell through a ball-and-socket joint that allows multi-directional movement. Under compression, collagenous ligaments rapidly stiffen, transforming a flexible joint into a rigid support structure. This reversible shift between flexibility and structural locking became the foundation of the wheel system.

Mechanical Translation

Biological Principle
to
Mechanical Strategy

- Flexible Joint -> Elastic Sphere Articulation
- Load-induced stiffening -> Deeper Socket Engagement
- Structural Locking -> Alternating soft and rigid zones

The result is a wheel cross-section that adapts dynamically to terrain.

System Architecture

The left one is smooth with a textured inner ring, and the right one is a gear with multiple smaller interconnected gears inside. 3D Printed with TPU

Alternating Soft & Rigid Zones

- Central rigid hub for structural integrity
- Elastic sphere modules along the rim
- Controlled compression channels
- Reinforced spoke geometry

Iteration & Prototyping

Two parts of 3D-printed objects, one white with a hollow center working as a rim, and the other black with six round protrusions inside a circular frame.

Prototype#2
ASA + TPU

The housing and internal chamber system were designed and assembled to support controlled airflow, layered biomaterial sheets, and separated heating and condensation zones.

Compression Testing

Mechanical compression testing evaluated deformation behavior under load.

The adaptive wheel demonstrated:
- Controlled localized compression
- Reduced abrupt impact compared to a solid tire

Testing validated that the sphere modules engage progressively under load and recover shape after release.

Final Prototype

System Behavior

Flat Surface
- Sphere modules move freely within cavities.
‍Impact / Threshold
- Spheres are pushed deeper into the socket, increasing contact stiffness.
‍Recovery
- Elastic modules regain flexibility, preparing for the next movement cycle.

This cyclical transformation mirrors the biological locking mechanism observed in sea urchins.

PHAT-CF & TPU Material Strategy

The prototype combines rigid and flexible materials to balance stability and impact absorption. PHAT-CF provides structural strength for the wheel frame, while TPU enables controlled compression that helps the walker move over small obstacles.

Final Prototype Part#1 printed with PAHT-CF

PHAT-CF

TPU

Images

Light softly diffuses from the back, while sound projects forward with clarity—two directions working in harmony within a single form.