DOG TREAT DISPENSER
Assistive tech designed to improve the experience of client with spinal cord injury.
Timeline
1 month
Role
Lead Human Factors Engineer
Skills
User Research
Prototyping
SOLIDWORKS
Team
2 Mechanical Engineers
2 Human Factors Engineers (Me)
Overview
We worked with our client, Ryan, and his service dog Oliver, for the duration of 1 month in our final project for my Engineering Design class. I collaborated with 2 mechanical engineers and 1 human factors engineer to research, prototype and build an assistive tech that improves the dog feeding experience of our user.
The Problem
What was our client’s pain point & need?
Problem Statement
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How might we develop a wheelchair-mounted, portable treat dispenser that enable Ryan to independently and easily deliver treats directly to his fingertips?
Key Objectives
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Enhance ease of operation & prevent accidental spills
Allow precise dispensing of single treats frequently throughout the day
Promote independence and reinforce Ryan’s bond with Oliver
Research
Understanding constraints & user needs using various methods
User Persona
👨
Ryan
Age
Mid-30s
Location
Greater Boston Area
Occupation
Nonprofit advocate & community organizer
Assistive Need
Motorized power wheelchair, service dog (Oliver), Personal Care Assistant (PCA)
About
Ryan sustained a C4 spinal cord injury following a mountain biking accident in Spain in 2011, resulting in significant paralysis from the neck down. Although he has regained some mobility and dexterity in his limbs, he relies on a motorized wheelchair and receives 24-hour assistance from a PCA for daily tasks.
Goals
Maintain independence in daily routines
Interact effectively with and reward his service dog
Stay active outdoors and participate in community events
Minimize reliance on assistance for small tasks
Pain Points
Limited hand dexterity makes opening treat bags difficult
Dropping treats often results in Oliver eating the entire bag
Traditional treat pouches are designed for able-bodied users
Treat storage can be hard to reach from a seated wheelchair position
Task Analysis
Existing Product Research & Market Gap
Developing Engineering Requirements
Design
Prototyping and iterating
Low-Fidelity Prototype
We rapid prototyped 4 low-fidelity cardboard prototypes, taking inspiration from existing mechanisms such as candy dispensing machines that use either a push force or a turning torque.
Major Takeaways
Using a push force feels more reliable & convenient
Storage & alignment of treats will be difficult to deal with
Control how a treat enter & exit the mechanism is crucial
Mid-Fidelity Prototype
Mechanism
Our mechanism is inspired by the rotary mechanism of a gumball machine. Our design includes a stationary & a rotating disc, where a motor connecting to a gear train would trigger the rotating disc.
Redesign Focus
Motorizing the mechanism instead of manual push
Change funneling system to prevent jamming
Change slide orientation to prevent jamming
Make dispenser shorter & more compact
Implement mounting system for wheelchair
Develop housing for battery & button
Our Solution
Our final product built in the makerspace
Final Product
Additions
Vertical slide to prevent dispensing jams
Shortened funnel to preserve space and condense product
Soldered button & bolted-in battery mount
Sliding track at top to attach to bottom of wheelchair arm
Complete casing around the mechanism
Product Teardown
All of our parts are securely attached between acrylic wall housing using bolts & nuts, and can be disassembled for cleaning.
Mounting Sliders: Securely attached to housing and allow our device to be mounted below the right armrest through sliding in a tracking
Funnel: Stores half a cup of treat, and loads individual treat into the rotating disc mechanism
Rotating Disc: Has 3 slot openings, allowing treats to be refilled constantly. It is spinning on a dowel connected to a gear train.
Stationary Disc: Has 1 slot opening that is connected to a chute. When the rotating disc lines up with that slot, a treat will fall through the chute
Motor Holder & Tracking: Holds the motor in place & provides support for the gear train & dowel
Battery Holder: Holds a 9V battery, which can be changed out when needed
Video Demo
Next Steps
What I learned & how we plan to move forward
What I learned
The most important takeaway from this project is learning to iteratively meet the user’s goals when designing an assistive tech product. We cannot assume what will work for the user, and have to base our design on data & user testing. Learning to prototype using SOLIDWORKS is also helpful to envision how different parts of the product will eventually fit together.
Future Direction
Use tabs and slots for a more secure casing
Add food-safe coating to the 3D printed parts
Make funnel and other parts detachable so that they can be cleaned
Change the circuitry so that one button press dispenses one treat instead of continuously having to holding it
© Ivy Chang 2026
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