Make a Von Frey device to test where your body are most touch sensitive
Suitable For
Grade 8
Difficulty
2
Time Required
<2 Days
Supervision
Advised
What’s it about?
Did you know that your skin is your largest organ? Your skin protects your inside organs while keeping infections out and prevents you from getting sick. A medium sized adult’s skin weighs about 3,5kg! A human being’s skin is sensitive to pressure, touch and temperature. In this science experiment, make your own ‘Von Frey device’ with fishing line of various thicknesses, to test the touch sensitivity of various parts of your friends’ bodies:
Topics covered
Von Frey
What will I need?
- RULER
- STICKY TAPE
- VARIOUS DIAMETER FISHING LINES
- MAGIC MARKER
- SCISSORS
- CRAFT (ICE CREAM) STICKS
- 5x FRIENDS
Procedure (Method)
Did you know that your skin is your largest organ? Your skin protects your inside organs while keeping infections out and prevents you from getting sick. A medium sized adult’s skin weighs about 3,5kg! A human being’s skin is sensitive to pressure, touch and temperature. In this science experiment, make your own ‘Von Frey device’ with fishing line of various thicknesses, to test the touch sensitivity of various parts of your friends’ bodies:
- Obtain about three different diameter samples of fishing line. The various types of fishing lines should be in the region of 0.15mm, 0.25mm and 0.4mm for best results.
- Cut off a length of about 60mm of each type of fishing line and use sticky tape to fix each piece of the line to the end of a craft stick so that about 40mm of it hangs freely from the tip of the stick.
- Use a thin point magic marker or a pen to mark the size of the fishing line on each craft stick.
- Draw a data table to record your observations as in the diagram above. Make column headings with the sizes of the fishing line and rows with the areas of the body to be tested, for example: Index fingertip, palm, wrist, inside forearm, outside forearm, cheek, neck, elbow and back of leg.
- Make copies of the table made in step ‘4’ for each volunteer or friend that are going being tested. Ask your volunteers to wear a short sleeved shirt and shorts for the testing session. All the tests have to be conducted in the same day as different weather conditions might influence the accuracy of the testing.
- Ask your first volunteer to sit at a table with his/her eyes closed and with his/her hands face up. Hold the ‘Von Frey device’ with the thinnest line over the test subject’s index fingertip, and gently lay the fishing line over the fingertip so that the line bends slightly. Ask your volunteer to indicate by saying ‘yes’ or ‘no’ whether he/she felt anything.
- Repeat step ‘6’ with all the areas of the body in your data chart and with all the thicknesses of fishing lines and record your results.
- Do this testing procedure with at least five of your friends or volunteers to obtain accurate results. Make a bar graph of your results indicating each volunteer’s data with a different colour!
How does it work?
In this science experiment, you tested the ‘skin detection threshold’ of various test subjects. This is the smallest amount of touch that a person can notice. A person’s skin has several touch receptors that trigger a series of nerve impulses when activated by touch. The various parts of the human body have different amounts of touch receptors on the skin. For example, there are a lot of touch receptors on the fingers and face, but a lot fewer receptors on the skin of the back and legs. You can only feel pressure, temperature changes or ‘touch’ when these receptors on your skin are triggered, and nerve impulses are sent to your brain for interpretation. The fewer receptors on a specific part of the skin, the least likely you are to ‘feel’ a sensation.
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