Animatronic Slime Project Update #1- Project Proposal and January Goals
- Matthew Saenz
- Jan 4
- 7 min read
From as early as high school, I have known that I want to work in the themed entertainment industry. Hugely positive childhood memories and the amazement I felt seeing Star Wars brought to life as I followed Galaxy's Edge updates from conception to opening are what drove me to apply to CMU, a school with deep ties to and history with the theme park industry, and become heavily involved in its Theme Park Engineering Group student org. Even now, as I am completing my work obligation to the SMART Scholarship Program with the Army Corps of Engineers, it remains my ultimate goal to work in themed entertainment. As my 9-to-5 has now left me with more free-time than I was accustomed to in school, I will be filling this time with a self-directed project combining my themed entertainment interests of animatronics and interactives this year. Welcome to my Animatronic Slime Project.
Project Overview, Motivation and Goals
Overview
For this project, I will create a diorama-style show scene depicting multiple slimes in a forest environment, complete with synchronized audio and lighting effects. Narratively, these are my pet slimes in their terrarium. The scene will feature two types of slime animatronic, one with a jumping animation, and one with a breathing animation. These slimes will be made using silicone rubber with a shiny finish in order to give the appearing of being wet and slimy. The motion of the slimes will be influenced through human interaction with the scene. I aim to complete this project within the year, with a tentative due-date of January 1st, 2027.
Motivation
Three key considerations informed my project proposal. The first was Novelty. It was important to me to find a unique concept and from my research, I could not find any animatronics in use today which depict "gooey" characters such as slimes using soft materials. My second consideration was Economic Feasibility. Cost was an intimating factor to consider during my brainstorming, with many concepts, especially involving full-sized humanoid animatronics, being rejected from budget concerns alone. With the smaller scale and lighter materials of the slimes, I expect to be able to achieve a well-realized final project on a modest budget. The final consideration was Surface Material Familiarity. As an electrical engineer, surfacing for an animatronic was my most obvious and immediate weak-spot. Fortunately I have some experience working with silicone materials from my Creative Soft Robotics class at CMU, which made it my top material choice, and further drove me towards a soft squishy subject such as slime.
Goals
My goals for this project are as follows:
To gain hands-on experience with professional grade themed entertainment controls hardware and software. In my previous student projects, budgetary and time constraints have forced me to hack together controls electronics and software using microcontrollers, single board computers, and Unity. This dedicated project will allow me the time and resources to do it "right."
To showcase my cross-disciplinary capabilities through a project containing elements of engineering and physical arts.
To demonstrate and apply my interests in animatronics and interactives in a project combining aspects of both.
To improve my project management and organizational skills through a well-planned and documented project. In previous projects I have tended to build the railroad as I go, so to speak, and as a result it has been difficult to showcase my entire start-to-end process in my portfolio. A major component of this project will be monthly project updates as both a means to keep me on track, as well as to self-document my creative and engineering process.
Proposed Slime Animations and Guest Interaction
Jumping Slime
The jumping slime will use two servo actuators to achieve a parabolic jumping trajectory. The first servo will drive a rack and pinion to control the horizontal motion of the slime. The second servo will be positioned at the end of the rack and pinion and will wind a fishing line reel to raise and lower the slime. The fishing line will be fed into the top of the silicone slime puppet with a stopper to prevent it from coming loose.
Through using just the vertical actuator, a second animation can be achieved of the slime jumping up and down in place. This animation will be used to express excitement in the slime when a human observer interacts with the terrarium (explained in greater detail later.)
Ideally the slime puppet will be partially filled with water or a viscous semi-solid to give a “jiggly” appearance like a water balloon, but this will be weight-dependent.
The jumping animation will consist of 3 stages:
In the slime's neutral pose, the fishing line will be held slightly in tension in order to hold the dome of the silicone slime puppet proud.
Just before jumping, this tension will be released, collapsing the dome. This will give the appearance of the slime “squatting” before it jumps.
Finally, when jumping, the reel will be retracted to lift the slime off the ground. Simultaneously, the horizontal actuator will move the slime from left to right (or vice versa). Both motions will be coordinated to trace a parabolic curve and synchronized to “squelching” sound effects.
Breathing Slime
The breathing slime will be inflated and deflated with water to mimic breathing. Additionally, this will be synchronized with the pulsating of an LED strip embedded beneath the surface of the slime puppet to enhance the effect. Originally, I proposed using a DC water pump and valves to achieve this, as is shown below. However, this effect may instead be achieved using a servo-actuated syringe, as it would be quieter and reduce the number of required control signals from 3 to 1.
Guest Interaction
While the breathing slimes are rather lazy and tend to stay put, guests will be able to interact with the energetic jumping slime. When guests wave at the terrarium, the jumping slime will excitedly jump in-place and chirp in response. This effect will be accomplished using a computer and webcam running a computer vision model trained to detect waving. When waving is detected, the computer will send a signal to the show controller to trigger the jumping in-place animation.
Project Timeline
My target project completion date will be January 1st, 2027. The project timeline will be broken into phases, with each phase focusing on a different component. This is done to focus my attention on one line-of-effort at a time, however each successive phase does not necessarily depend on the previous phases, granting me flexibility to shift focus should I become stalled on the current phase. The proposed project phases and timing is as follows:
Phase 0 - Project Conception and Initiation: December 2025 - January 2026
Phase 1 - Slime Puppet Development: January 2026 - March 2026
Phase 2 - Mechanical Design: April 2026
Phase 3 - Controls Engineering: May 2026 - August 2026
Phase 4 - Interaction Integration: August 2026 - September 2026
Phase 5 - Terrarium Construction: September 2026 - October 2026
Phase 6 - System Testing and Installation: November 2026 - January 2027
The full project timeline with a detailed task list can be viewed in a modified Gantt Chart format here.
Current Progress
I began Phase 0 last month by creating a Project Proposal pitch deck outlining the project concept, motivation, goals, timeline, and some implementation details (aka, what you have just read above, but in greater detail.) Over the course of December, I shared this proposal with friends and mentors to garner feedback and iterate the project plan to a point I felt comfortable beginning from. That proposal can be found below.
In addition to the Project Proposal, I have begun on a rough CAD sketch of the terrarium to familiarize myself with FreeCAD (as I no longer have a student license for Solidworks) and get a sense of scale. Using a typical 40 gallon reptile terrarium (36"x18"x18") as reference, I scaled the slimes to a 3" radius, 4" height to start. By being taller than its radius, the slime dome is given a slight bulge before tapering back in at the base, which I feel supports the squishy shape language I am looking for in the slime design.
January Goals
My first goal for this month will be to select the silicone rubber I will use for the project. I had previously identified Smooth-On's Ecoflex product line as my choice of silicone, as the cured silicones have low hardness and density. I believe these qualities are important for the slime puppets, as the low hardness will give a squishy appearance, and the low density will make it easier to lift the jumping slime puppet. However, if the hardness is too low the puppets may tear, and the product description for the lowest density Ecoflex variant indicated that it has a tacky texture when dried, which may inhibit lifting the jumping slime. For this reason I have purchased Ecoflex 00-10, the lowest hardness variant available on Amazon, and Ecoflex 00-40, the highest hardness variant, to test. I will compare their appearance, "tint-ability," density, and durability to determine which variant will best suit the project.
Alongside this effort, I will begin to design and prototype the puppet molds using FreeCAD. These molds will be printed using my workplace's 3D printers, using my own filament. I will need to determine how to design the mold to leave a hollow cavity in the center of the finished slime puppet. My current plan is to cast the slime puppets in two parts, the top dome and a bottom round plate, then use additional silicone to glue the two halves together.
Finally, when I have selected the silicone rubber to be used and have a prototype mold ready to test, I will begin testing on the puppet manufacturing. I am targeting having my first puppet shell prototype cast by the end of the month. This will lead into February, where I will continue to iterate the slime puppet shell design and begin to test different puppet fillings to achieve a jiggly texture while minimizing puppet weight.
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