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Identity: How are Fingerprints Transferred and Analyzed?

based on 17 ratings
Author: Janice VanCleave

Problem

How are fingerprints transferred and analyzed?

Materials

  • Transparent tape
  • Desk lamp
  • Magnifying lens

Procedure

  1. Tear off about 1 inch (2.5 cm) of transparent tape and stick it across the tip of your index finger.
  2. Remove the tape from your finger.
  3. Hold the tape so that the light of the lamp shines through the tape.
  4. Examine the tape by looking at it through the magnifying lens.
  5. Identify the pattern formed by your fingerprint by comparing it with the three basic fingerprint patterns: whorl, loop, and arch.

Identity

Identity

Results

A copy of your fingerprint is left on the sticky side of the tape.

Why?

Your body has two layers of skin. The outer skin is called the epidermis, and the deeper second layer of skin is called the dermis. The boundary between the dermis and the epidermis is not straight and smooth; it consists of small folds. These folds produce a series of ridges and grooves in areas where the skin is thick: the palm of the hand, sole of the foot, and fingertip, for example. The patterns formed by the ridges on the fingertips are called fingerprints. There are three basic fingerprint patterns-whorl, loop, and arch—but no two people have been found with exactly the same fingerprints. Beneath the surface of the epidermis are oil—producing glands. A thin layer of oil from these glands collects on the fingertips. When the tips of your fingers touch anything, a little oil in the form of a fingerprint is left.

Try It With A Microscope

Microscope Procedure

Identity

Identity

Identity

  1. Place a piece of transparent tape on a microscope slide and observe the tape under low power. This will make you familiar with the magnified surface of the tape so that you will not mistake it for part of your fingerprint.
  2. Rub the sharpened end of a pencil across a sheet of paper 15 to 20 times to collect a layer of graphite on the paper.
  3. Rub your index finger across the graphite on the paper.
  4. Tear off about 1 inch (2.5 cm) of tape and stick it across the graphite on your finger.
  5. Remove the tape and stick it to a second, clean microscope slide.
  6. Slowly move the slide around as you observe it under low power.

Microscope Results

The surface pattern of the tape can be seen beneath the wide rows of black clumps of graphite. A single row of graphite covers most of the viewing field. The rows are not in straight lines, but curve.

Let's Explore

  1. Do each of your fingers have the same fingerprint pattern? Repeat the original experiment, examining the prints from each fingertip. Science Fair Hint: Make an outline of each hand on separate sheets of typing paper. Rub the fingerprint of each of your fingers in powdered paint. Collect the colored fingerprints with clear tape as before. Place each piece of tape on the corresponding finger in the hand diagrams. Identify the pattern for each fingerprint taken. Use the diagrams as part of a science fair display.
  2. How do fingerprints of the same basic pattern differ? Use a magnifying lens to compare the prints from two people with the same basic fingerprint pattern. Determine the differences in the prints.

Show Time!

Does everyone in the same family have the same basic fingerprint pattern? Prepare print samples from the index finger of each family member. Ask each person to press his or her finger against an ink pad and then against a sheet of typing paper. Label the print with the person's name and relation to you. Prepare a poster with the prints, and use them as part of a project display.

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