Prosthetic Liner Donning Device

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Prosthetic Liner Donning Device
Team Name Snap Into Motion
Duration Fall 2013 - Spring 2014
Faculty Advisor Dr. Tom Hess
  • Chris Ohlinger
  • Matt Kologi
Team Members
  • Samantha Sutherland
  • Jordan Simonson
  • Matthew Guthrie
  • Jennifer Rainey
  • Allyson Labrum

Snap into motion is a senior capstone design team that is dedicated in designing a system to enable independent liner donning for transtibial amputees. Our project is to design a device to aid lower limb amputees in donning their prosthetic liner. The device will ensure that the liner sits flush against the limb, properly aligns the pin into the prosthetic, and enables those with low hand dexterity, vision, or flexibility to don their liner independently.

Design Task

2014 SnapIntoMotion PatientDonning.jpg
Nurse Helps Transtibial Amputee with Donning Prosthetic Liner

There are approximately 34,000 transtibial amputations performed each year in the United States. The causes of these amputations range from infection to tumors with the most prevalent causes being diabetes and severe traumatic injury. Patients with transtibial amputations that wish to use a prosthetic leg must wear a prosthetic liner that protects their skin from the rough prosthetic leg materials and helps suspend their leg in the prosthetic. Prosthetic liners can be difficult to don, especially for patients with limitations in flexibility, hand dexterity, or vision.

Our goal is to create a mechanical system that will allow patients to independently don their liner and:

  • Comfortable
  • Easy to use
  • Work with commercial liners/prosthetic components
  • Accommodate the majority of patients
  • Reduce strain for the patient
  • Require little to no hand strength or dexterity
  • Aid inflexible individuals
  • Properly align the pin

Design Specifications

General Requirements
Allow for patients to align and don liner themselves easily
Source: Original project specifications
Align pin every time liner is donned
Source: Original project specifications
Allow independence for amputee
Source: Original project specifications
Accommodate all liner sizes and brand variations
Source: Original project specifications
Must be easy to use for patients with low hand dexterity and limited flexibility
Source: Original project specifications
Ergonomic Design
Source: Client interview on 10/3/2013
Work with existing external liner materials
Source: Client interview on 10/3/2013
Possibly assist with removing liner
Source: Original project specifications
Specific Requirements
Design must work with liners of distal diameter from 2.5" to 12.0"
Source: Personal research based on information from client interview on 10/3/2013
Design must work with liners of proximal diameter from 3.1" to 11.7"
Source: Personal research based on information from client interview on 10/3/2013
Design must work with liners of length from 12" to 16"
Source: Personal research based on information from client interview on 10/3/2013
Pin size: Device must accomodate for pin which measurements are as follows: Diameter: 10 mm, Length: 1"-2.25", Pitch: 1.5 metric
Source: Client interview on 10/3/2013

Project Learning

Background Research

Dimensional Analysis of Transtibial Roll-On Style Prosthetic Liners

  • Distal diameter ranges from 2.5" to 12.0"
  • Proximal diameter ranges from 3.1" to 12.0"
  • Target lenght of liners ranges from 12.0" to 16.0"
  • Pin lengths have a standard diameter of 10 mm, standard pitch of 1.5 metric, and varying lengths from 1" to 2.25"


Interviewee Overview
Lisa Huffman

Client Interview on 10/3/2013

Background Information on Patients

  • The general patient description is 60 years of age, overweight, reduced vision, decent hand function (arthritis can be an issue however), and cannot reach past kneecaps. Many cannot bend further than 90 degrees at the hip due to obesity.
  • Patients have trouble donning their liners due to these issues
  • Liners can vary from patient to patient. They are made of different materials and have varying thicknesses. A patient with a higher activity level means they need a more substantial liner.
  • All of her patients use the pin-locking liners for their prosthetics

Concept Development

Drive Design Alternatives

Design Description Pros/Cons
2014 SnapIntoMotion paralleltracksystem.png
Parallel Track System

For this concept, a quadpod would be used so that the user could adjust the height to accommodate the level at which users may be sitting. The track would be mounted using a pivot joint to account for the angle at which the user would be sitting. The parallel tracks would be attached to arms. The tracks would use a rack and pinion system for motion. The prosthetic liner would be folded over the arms and, as the tracks moved linearly toward the user, the liner would be donned on the leg.

  • High Torque Capabilities
  • Precise and Reliable
  • Deflection Eliminated in Donning Process
  • Simple, Accurate Design


  • Large, Bulky System
  • Unstable Due to Elevated Mounting
2014 SnapIntoMotion linearactuator.png
Linear Actuating System

Similar to parallel track system, however, instead of using a rack and pinion system, linear actuators would be on each side of the user with arms mounted to them. The arms would have expanding capabilities to accommodate the change in circumference of the residual limb. Using non-simultaneous donning, the device would mimic the hand motion most often associated with donning; one hand pushes up at a time. Through limited testing, the non-simultaneous donning proved to require less force to don.

  • Simultaneous or Alternating Actuation
  • Compact Design
  • Position/Feedback Control with Potentiometer Capabilities


  • Multiple Actuator Timing
  • Unstable Arms
  • High Cost
Whole System
Ramp that the glider track will rest on
Glider Track System

This concept utilizes and exterior approach rather than the interior approaches discussed with the previous design alternatives. The glider donning system utilizes a carriage that glides along a single track. Attached to the carriage are two horizontal actuators which function to move the garter hands onto and off of the liner. The garter hands are spring loaded so that they can accommodate the width of the residual limb. The whole system is attached to a ramp that can adjust to different heights according to the user's chair height.

  • Single Track System
  • Horizontal or Elevated
  • Force/Speed
  • Ground Support
  • Adjustable
  • Accommodates Dynamic Loading
  • Comfortable for User


  • Possible Arm Deflection

Garter Design Alternatives

A garter is what we have named the device that will be mounted on the end of the device's arms and will be the part of the device that comes in direct contact with the patient's liner. It is named a garter because it needs to expand and accommodate different sizes of the leg.

Garter Alternative Overview
Multiple Finials
2014 SnapIntoMotion multiplefinials.jpg

  • The concept is composed of multiple components that have small surface area.
  • The finials can be made of a variation of shapes (spheres, t-bars, etc.)
  • Does not allow for the equal dispersion of forces and one finial can sometimes be required to bear the load of two or more finials.
Crescent Shape
2014 SnapIntoMotion crescentshape.jpg

  • This concept contains an arm that ends in a crescent shape.
  • Concept would be composed of 2-4 crescents
  • Allows for a greater dispersion of forces than multiple finials due to larger surface area
  • Does not allow for a lot of give when it comes to patients with larger liner sizes
Donning Hand
2014 SnapIntoMotion donninghand.jpg

  • The concept is composed of garter that will surround a larger circumference of the leg than the crescent shape
  • Disperses forces even more equally than the crescent shape alternative
  • Contains pivot joints to accommodate the change in a leg's diameter
  • Has a "hand" curvature to mimic a person donning a liner

Design Decision Matrix

We compared the drive design concepts in a design matrix that was scaled from 1-5. Based on the matrix, we decided to follow through with the glider track system with the donning hand. Below is the link to the design matrix:

Concept Testing

Test Photo Overview Results
2014 SnapIntoMotion Fishscale.jpg
Force Test on Donning Liner

A fish scale is being used to measure the force required to don the liner using two hands that are attached to the scale at the wrists using string.

Four tests were completed and the average of the force at each two inch mark was compiled.

The results can be found in the link below:

Liner Donning Force Test Results

Final Design

Design Specifications

Whole System

After more project learning and design, we arrived at a final design.

2014 SnapIntoMotion WholeSystem.jpg

The subsystems include:

  • Linear Track & Linear Actuator
  • Linear Applicator
  • Adjustable Stand
  • Liner Loader

A diagram showing how the donning process will work using this design is shown below.

2014 SnapIntoMotion DonningDiagram.png
Updated Specifications
General Requirements Specific Requirements Target Values
Size Dimensions (LxW) 36" x 26"
Physical Characteristics
  • Weight
  • Surface Texture
  • Impact Resistance
  • 25 lbs
  • Smooth Finish
  • 200 lbs
Components (Manufactured)
  • Liner Loader/Umbrella Cup
  • Diameter
  • Length
  • Liner Applicators
  • Radius of Curvature
  • Material
  • Outer Coating


  • 1"/3"
  • 16"/2.5"


  • 2.15"
  • Aluminum
  • Leather Pad
Components (Purchased)
  • Linear Actuators
  • Voltage: 12V DC
  • Stroke Size: 4"
  • Load Capacity: 35 lbs
  • Speed: 2.00"/sec
  • Type of duty: 25%
  • Operational temp:-25ºC~+65ºC
  • Protection class: IP54
  • Low Noise: db<45 (A)
  • Certification: CE
  • Built-in limit switches, not adjustable
  • Product Weight: 1.75 lbs
  • Track Actuator
  • Voltage: 12V DC Linear
  • Actuator
  • Stroke Size: 22"
  • Load Capacity: 150 lbs
  • Speed: 1.30"/sec (150 lbs)
  • Type of duty: 10%
  • Operational temp: -5ºC~+40ºC
  • Protection class: IP65
  • Low noise level: 48dB(A)
  • Certification: CE
  • Built-in limit switches, not adjustable
  • Product Weight: 7.65 lbs
User Requirements
  • Ease of use
  • Ease of learning
  • Operator Training
  • Difficulty scale 1-5: 1=easy, can be done independently; 5=difficult, may need assistances
  • 1: On/Off/Pause/Restart Control
  • 2-3: Adjusting/Situating themselves in the device
  • 4-5: Read instructions and calibrate device
  • Reliability
  • Service requirements
  • Ease of repair
  • High
  • 1.5 years
  • Requires technician
Performance Characteristics
  • Accuracy
  • Strength
  • Repeatability
  • Speed
  • Duty Cycle
  • Friction Factor COF
  • .98
  • 15 lbs
  • .98
  • 3in
  • .02ms
  • 0.2-1.7
Environmental Requirements
  • Operating range
  • Compatibility with liners
  • 0-6 amps
  • Ossur USA, Ohio Willow Wood, and ALPS, silicone elastomer and liners

Subsystem Concept Development

Linear Applicator

The two linear applicators are what will be in contact with the prosthetic liner and move it up the user's residual limb. There will be pressure sensors that will measure the pressure being applied to the liner/residual limb so that no discomfort or pain will come to the user.

2014 SnapIntoMotion LinearApplicator.jpg









Linear Track & Linear Actuator

There will be two linear tracks on either side of the stand. The tracks will move towards the user's hips during the donning system while the linear actuators move towards the user's residual limb simultaneously to move the prosthetic liner up the residual limb. Once the pressure sensors that are on the linear applicators reach a certain pressure, the linear actuators will move off of the limb and the linear track will move away from the user approximately 1 inch. This process will continue until the liner is fully donned.

Linear Track

2014 SnapIntoMotion LinearTrack.jpg

Linear Actuator

'Linear Actuator'
Adjustable Stand

The adjustable stand will allow for people to set the device at a height that is comfortable for them. It has yet to be decided if this will be at an angle,using a scissor stand, or both integrated together.

Liner Loader

The liner loader is where the user will place the prosthetic liner before the donning process begins. The liner's pin will be guided and locked into the liner loader and then inverted over the liner loader. The liner loader will be a detachable stem so that this is can all be done free of the rest of the donning system. The liner loader is then locked into the stand using a locking mechanism at the end of the stand.

2014 SnapIntoMotion LinerLoader.jpg
Control System

We will be using an arduino uno microprocessor as our control system. The pressure sensors on the linear applicators will be our input and as an output, the microprocessor will control the movements of the linear track and linear actuators.

Final System

2014 SnapIntoMotion FinalSystem.jpg

Project Budget

Linear Actuators (2)

$109 each x 2 = $218

Track Actuators (2)

$140 each x 2 = $280

Control System


Liner Loader


Adjustable Stand




Team Members

2014 SnapIntoMotion TeampicNew.jpg
Pictured left to right:

Top: Matt Guthrie and Samantha Sutherland

Bottom: Jennifer Rainey and Jordan Simonson

2014 SnapIntoMotion Matt2.jpg

Matt Guthrie

Mechanical Engineering Student


I am a mechanical engineering student with a passion for prosthetic improvement and an interest in biomechanics. Ultimately I will strive to invent systems that will benefit people around the world. My interests include: playing piano (music in general), skiing/snowboarding, and machining.

2014 SnapIntoMotion Jennifer.jpg

Jennifer Rainey

Biological Systems Engineering Student


I am a biological systems engineering student at the University with an interest in medical device development and production. I have interned with a Lead-Lok, Inc., a biomedical innovations company out of Sandpoint, Idaho for the past three summers. I hope to use this background experience to start a career in the medical device industry. I enjoy hiking, kayaking and reading.

2014 SnapIntoMotion Jordan.jpeg

Jordan Simonson

Biological Systems Engineering Student

Email: simo6466@vandals.uidaho.ed

I am a biological systems engineering student here at the University of Idaho and I am extremely interested in how the human body works and how we can improve it to work better. I hope to invent products that make the quality of life better for every single person. For fun, I like to go skiing and play fetch with my puppy.

2014 SnapIntoMotion Samantha.jpg

Samantha Sutherland

Biological Systems Engineering Student


I am a senior at the University of Idaho graduating May 2014 with a degree in Biological System Engineering. For the past two years I have been working as an engineering intern in the research and development department at Schweitzer Engineering Laboratories. Upon graduation, I plan to join a medical device manufacturing company.

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