Alginate Worms
- Page ID
- 131587
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Required Training |
Required PPE |
|---|---|
|
UC Lab Safety Fundamentals |
Lab coat, safety glasses/goggles, nitrile gloves |
|
Equipment |
Chemicals |
|
1600 mL beaker |
Alginate powder |
|
1 L plastic bottles |
Sodium chloride (CaCl2) |
|
10 mL syringes |
Blue thermochromic pigment |
|
1 L plastic dish |
Fluorescein (pure) |
Procedure: (Prepare 2-3 days ahead of time)
1.) Preparation of Alginate Gel (DO NOT HEAT)
Pour 1 L DI water (NO tap water) into a large beaker and begin vigorously agitation using a stir bar/plate.
Add 1 % (10 g) alginate power. It will clump into sticky globules.
Leave stirring overnight or until powder completely dissolves.
Add 0.4% (4 g) thermochromic pigment or 0.1% (1 g)fluorescent dye. Again leave stirring.
Store alginate gel in a plastic container (will stain) and distribute to small squeeze bottles.
2.) Preparing 0.1 M Calcium Chloride solution.
Combine 1 L DI water and 11.1 g CaCl2, stir until completely dissolved.
3.) Poor 500 mL CaCl2 into the plastic dish then use the 10 mL syringes filled with alginate gel to make worms.
Clean-up: Alginate gel is biodegradable and can be thrown away, but should not be poured down the drain due to its viscosity. Thermochromic and fluorescein alginate gel can be thrown away.
Hazards: Alginate is not classified as hazardous. Although considered to have dietary fiber properties and is edible, the alginate used here is not food grade and is exposed to laboratory environments. The pigments/dyes make the material unsafe to handle without gloves.
Principle: Alginate is a naturally occurring polysaccharide at levels of 30-60% in certain species of brown algae. It provides flexibility and the ability to withstand tidal forces. These structural elements are demonstrated in the demo. When sodium alginate is placed into a solution of calcium ions, the calcium ions replace the sodium ions. Unlike sodium which can only form one bond and therefore attach to one alginate molecule, calcium is able to form two bonds, meaning it can attached to two alginate molecules. This cross-linking of alginate molecules allows for polymerization to take place, making the gel more rigid. The longer the exposure to the calciumhloride solution, the more sodium is displaced, the more crosslinks formed, the more rigid the gel.
Notes: DO NOT heat, gel is stable up to 150ᵒC but prolonged exposure will destabilize the gel. If air bubbles get trapped in the gel, let it rest in a fridge for a few hours or place in a vacuum chamber.Alginate gel concentrations can range from 0.5-1% for spherification. Up to 1.5% for other applications. Alginate does not gel at pH below 3.7. For dispensing gel, it is best to use syringes or other materials that have immediate access to the solution (i.e. typically squeeze bottles with long tubes only produces spheres, not worms). 10 mL syringes are best as 1 mL is too little to produce enough force to produce a worm and any larger volume will result in too much waste (kids will use everything in the syringe).