Feather: Prosthetic Leg

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This project was done in a five person group and my role was the mechanical designer and fabricator.

The Feather was designed to be a customizable transfemoral prosthesis with a single-axis hydraulic return knee joint, carbon fiber attachable plates, and an adjustable dynamic response foot. Compared to other prosthetic legs in the market, the main focus of The Feather was making it light-weight and aesthetically pleasing.

We had a specific case study we were designing for:

A 13 Year old girl that enjoys drama and K3 activities and would also like to engage in social and intimate relationships. Her original prosthetic consisted of a endoskeletal transfemoral prosthesis, polycentric knee, single-axis foot, and flesh colored cover. Her main problems with her original prosthesis was the heavy-weight and the poor aesthetics.

Looking at a greater overall design problem of designing for a growing teenager, we needed to make the leg highly-customizable, easy to produce and make parts for, and durable for daily teenage life.

We came up with several designs before settling on a single design that combined all the best aspects of the others – A carbon fiber prosthesis with a single-axis hydraulic knee and attachable aesthetic plates.

Through research and interviews, the team decided to address the common problems of heavy weight, fashion vs. discretion, identity vs ability, and provocative vs sensitive.

Thus, The Feather was broken down into three main components of the prosthetic leg:

– The Knee Joint

– Customizable Prosthetic Leg Covers

– The Dynamic Energy Foot with the Adjustable Ankle

Which are discussed in-depth below:

The Knee Joint:

A single-axis hydraulic knee joint offers a lightweight and mechanically simple design that has a high potential for modularity and upgrades.

Single - Axis Hydraulic Knee

Offers a mechanically simple and easily upgradeable solution for prosthetic knee joints.

Hydraulics

The hydraulic system is capable of being adjusted from the spring for energy return and with the damping fluid for shock absorption.

Cover

Holds everything together

Joint and Socket Attachment

A spherical joint allows for a more streamline aesthetic attached to a socket attachment design.

Socket Attachment

Follows a normal screw tightened socket adapter.

Hydraulics Internal View

Shock absorber attached to joint design.

Hydraulic System

Hydraulics system covered.

Fully Assembled System

Attached to the leg and socket adapter.

Customizable Prosthetic Covers

The aesthetic plates are made with blue carbon fiber that is both lightweight, flexible, and durable. These can also be easily switched out to suit different situations that users deem fit.

Front and Back Cover

Customizable covers can be interchanged into other ones made through a basic mold.

Cover Mold

Based off of a mold of a leg.

Vacuum Formed

Vacuumed for the exact shape and contour of the leg covers.

Vacuum Formed

Process of taking the covers off the mold.

Covers Untrimmed

Before the custom trimming.

Trimmed

Trimmed and cut to specifications.

Layer of XTC3D

A layer of epoxy to add shine and extra durability.

Front Completed

Front side completed with another layer of epoxy.

Back side of Leg Covers

Completed and trimmed back leg cover.

Two Parts Together

Both completed and matched to fit.

The Dynamic Energy Foot and Adjustable Ankle:

This foot was based on the Freedom Innovation’s Runway Prosthetic Foot, however it was redesigned for more limited and cheaper manufacturing facilities.