Gel Diffusion Experiment. STEM ED/CHM Nanotechnology 2013 Presented by Jennifer Welborn. Learning Goals. In this activity, nanotech participants will: See how food dyes and gelatin are used to model the delivery of nanoscale medicines to cells in the human body
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Presented by Jennifer Welborn
In this activity, nanotech participants will:
Diffusion– movement of a substance from a region of higher concentration to a region of lower concentration.
Diffusion continues until equilibrium--- the concentration of a substance is equal throughout a space
Carbon dioxide from the environment diffuses into plant cells
Syringes/10 ml graduated cylinders
Prepare Gel Disks
Determine amount of water needed to fill up a pan to a depth of 1 cm.
Dissolve gel into cold water (2Pks/Cup/200 ml)
Microwave for 90 Sec.
Pour into pan which has been coated with petroleum jelly and let set.Lab Prep
Cut disks--bisquit cutter
Thin coating of Petroleum jelly on inside bottom of Petri dish
Put gel disk –top side down and centered- on bottom of dish
Gently press disk to secure
Mix dyes in cups
Inject one color/petri dish
No dye on top of gel
No seepage under gel
Do not move dishes after dye insertedLab Procedure
Diffusion is first visible
Load the first morning shot
Windows Photo Gallery or other image program
Using a mm ruler, measure from the edge of the gel disk to the inner most edge of the diffusion for each color.
For the last time period measured and for each color
of dye, calculate and record the mean percentage
Use: total distance traveled by dye in mm / 32.5 x 100 = ________%
Record the mean percentage of diffusion for each color in your data table or spread sheet
Then click on trim and use image
of the petri dish
Record petri dish diameter and units
Click on the blue and red adjustment tools to help you place the blue and red dots at
The beginning and end of the line
Draw a line from the edge
of the gel to where the diffusion of dye molecules appears to end
Note length of line
Zoom in to see diffusion line
and edge of gel more clearly
You can also use ADI software to see a qualitative graph of the diffusion of the yellow dye molecules at a particular time. You can compare the qualitative graph with the quantitative measurements. A qualitative graph also helps to see that diffusion is a dynamic process with a trend in movement but no clear end point.
Gel going through the diagonal
Choose line tool option
red, green and blue pixels along the line drawn
across the gel. Notice that around 20/100 the lines level off, indicating edge of diffusion
If you turn off all colors but green, you can more easily see that around both 20 and 80 is where the diffusion of the dye molecules tapers
off. So, diffusion of the yellow dye particles at this time interval is about 20/100, or .20. Compare this with 1.09 (diffusion distance)/6.03 (gel diameter) = .18
Youtube video made by the Center for Hierarchical Manufactoring at UMASS, Amherst: