Squishies are soft-matter engineering. Today you are not just making toys. You are testing how materials deform, absorb force, return to shape, and send calming touch information through your hands.
No eating lab materials. Wash hands after testing.
Do not heat, freeze, microwave, cut open, or pressure-test commercial squishy toys.
Use gloves at messy stations. Avoid latex balloons if anyone has a latex sensitivity.
Teacher controls contact solution or any borate activator. For younger students, skip slime-gel and use cloud dough, flour dough, and oobleck.
No sealed container pressure experiments. Squishy pouches are for gentle hand squeezing only.
Big Question
What makes a material satisfying to squeeze, and how can we design one safely?
Good squishy materials are usually soft, stretchy or moldable, slow to rebound, and able to recover at least part of their shape. Different recipes feel different because they behave like different kinds of matter: foams, gels, pastes, fluids, and viscoelastic solids.
Teacher Opening
Hold up a sponge, marshmallow, foam piece, dough ball, and squishy toy. Ask: which one is soft, which one is stretchy, which one is slow, and which one pushes back?
Say: Newton's laws tell us your hand applies force. Materials science tells us why each object answers that force differently.
Transition: Today our job is to design a safe squishy and test it like materials engineers.
Key Vocabulary
ElasticityHow well a material returns to its original shape.
PlasticityHow much a material stays deformed after force is removed.
ViscosityA material's resistance to flow.
ViscoelasticityActing partly like a liquid and partly like a spring.
ReboundHow quickly something returns after being pressed.
Tactile FeedbackInformation your hands and nervous system receive through touch.
Intro Simulation: How Materials Answer a Squeeze
Use this at the beginning of class. Pick a material, press the test blob, then ask students to predict which classroom recipe will feel most similar. This is a simplified spring-particle model: it helps compare rebound and squishiness, but it is not a molecular, fluid, or foam-cell simulation.
Drag the squishy or press it with the plate.
Cloud Dough
Soft paste: slow squeeze, gentle shape recovery, good for dumplings and mood blobs.
Class question: Is this more like a spring, a liquid, a foam, or a paste?
4. DesignCreate a dumpling, creature, cube, blob, or stress object.
5. TestMeasure rebound time, shape memory, satisfaction, and durability.
6. ReflectChoose which material best matches a stress ball, squishy toy, oobleck pouch, or memory foam.
Station A: Cloud Dough Squishy
Best for: young students, dumplings, soft blobs, sensory forms.
Mix 2 parts cornstarch with 1 part conditioner or lotion.
Add color if needed. Knead until smooth.
Add cornstarch if sticky; add conditioner if too dry.
Science: A soft paste made of solid particles suspended in a creamy liquid.
Station B: Flour Stress Dough
Best for: dense hand resistance and stress-ball style filling.
Mix 1 cup flour, 1/4 cup salt, and 1-2 tablespoons oil.
Add water one spoon at a time. Knead until smooth.
Place into a latex-free balloon, vinyl glove finger, or sealed sensory bag.
Science: A granular paste that can resist compression and slowly deform when squeezed. Its behavior depends strongly on how much water and oil are mixed in.
Station C: Oobleck Pressure Squishy
Best for: non-Newtonian behavior and force-response testing.
Mix 2 parts cornstarch with 1 part water.
Place in a strong zip bag and double-bag it.
Compare a slow squeeze with a fast tap or quick squeeze.
Science: Oobleck is shear-thickening. Under sudden shear, cornstarch particles crowd and jam; under slow motion, they have time to slide past one another.
Station D: Slime-Gel Squishy
Best for: older students only, with teacher-controlled activator.
Mix 1/2 cup glue, 1/2 teaspoon baking soda, lotion, and color.
Add contact solution a few drops at a time.
Stop when it becomes stretchy. Store in a sealed bag.
Science: Borate activator cross-links glue polymers into a flexible gel network.
Memory Foam Comparison
Do not make polyurethane foam in class. Instead, compare a memory foam sample with sponge foam.
Press each foam for 5 seconds.
Release and count return time.
Describe the feel: springy, slow, sinking, or bouncy.
Memory foam is usually a viscoelastic polyurethane foam. Its slow return comes from polymer viscoelasticity plus the structure of tiny foam cells.
Design Challenge
Build a one-hand squishy object: dumpling, creature, cube, stress object, planet, mood blob, molecule, or memory-foam monster.
It must be safe to squeeze.
It must return partly to shape.
It must have a face, texture, label, or theme.
It must name the material family: dough, gel, oobleck, foam, or hybrid.
Testing Lab
Test
What to Do
What to Record
Rebound Time
Press for 5 seconds, release, and count.
Seconds until it mostly returns to shape.
Shape Memory
Draw original, squeezed, and recovered shapes.
Did it recover, stay dented, flow, or crack?
Squeeze Satisfaction
Rate softness, smoothness, stretch, slow return, and stress-relief feel.
Use a 1-5 scale for each category.
Durability
Squeeze 20 times gently.
Did it leak, tear, dry, crumble, or survive?
Newtonian vs Non-Newtonian
Concept
Meaning
Squishy Example
Newton's laws of motion
The force framework: pushes, pulls, motion, and action-reaction.
Your hand squeezes; the squishy pushes back.
Newtonian fluid
A fluid with mostly constant viscosity.
Water or oil flows predictably.
Non-Newtonian fluid
A fluid whose viscosity changes under stress.
Oobleck gets harder when hit.
Viscoelastic solid
A material that acts partly like a spring and partly like a slow-flowing material.
Memory foam slowly returns to shape.
Classroom phrase: Newton's laws tell us that your hand applies force. Non-Newtonian materials show us that not all fluids respond to force in the same way.
Student Fallback Checklist
Choose one safe recipe and write the material name.
Build a one-hand squishy shape.
Test rebound time after a 5-second press.
Rate softness, smoothness, stretch, slow return, and stress-relief feel from 1 to 5.
Explain what you would change in version 2.
Name one real-world object that uses a similar material: shoes, helmets, pillows, packaging foam, prosthetics, therapy tools, sports padding, or car seats.