Gel Diffusion Experiment STEM ED/CHM Nanotechnology 2009

Set-up Collect materials Collect materials –Petri Dishes –Food Dye –Syringes –Paper Cups –Gelatin –Crisco/Petroleum Jelly –Baking Pan Prepare Gel Cast Prepare Gel Cast –Determine water needed for proper coverage in pan –Dissolve Gel into warm water (2Pks/Cup) –Microwave for 90 Sec. –Pour into pan and let set.

Setup Gel Cast Gel Cast –Cut circles in pan w/metal cookie cutter –Remove excess –Move Gel Cast from pan and transfer to Petri Dish –Smooth side Down! –Centered as best can Adding Dye Adding Dye –Mix dyes in cups –Inject one color/dish –No dye on top of Cast –No seepage under cast –Do not move dishes after dye inserted

Collect Data and Observations Take Digital photos –S–S–S–Same time each day and at same interval 8:00 AM and again at 4:00 PM each day –F–F–F–From approximately same height and angle –H–H–H–Helps to have a good background under the Petri dish

Gel Diffusion Analysis Nanotechnology Institute 2008

Image Analysis Method 1: –Measure the dye penetration distance each day using a ruler –Use graph paper to plot distance vs. time –The rate is the slope of the line

Measurement by Hand

Image Analysis Group Pictures by Color in date/time order Group Pictures by Color in date/time order –Create a data table (paper or Excel)

Pick one color to start Pick one color to start Load the first morning shot Load the first morning shot –Windows Photo Gallery or other image program

Using the magnifier expand the photo Using the magnifier expand the photo With a MM ruler measure the gel cast With a MM ruler measure the gel cast Next measure from the edge of the gel cast to the inner most edge of the diffusion Next measure from the edge of the gel cast to the inner most edge of the diffusion

The ratio of the diffusion measurement divided by the gel cast measurement multiplied by 60 equals the amount of diffusion The ratio of the diffusion measurement divided by the gel cast measurement multiplied by 60 equals the amount of diffusion (15 mm/145 mm) x 60 mm = (15 mm/145 mm) x 60 mm = Enter this number in the appropriate column of your data table Enter this number in the appropriate column of your data table Repeat for all time periods and colors Repeat for all time periods and colors

When finished your table might look something like this When finished your table might look something like this

Use the graphing wizard to complete the project. Use the graphing wizard to complete the project.