Nanotechnology and Human Health

How Small are Nanoparticles Measured on the Nanoscale?

The size of a nanometer can be visualized through mathematical representations, relative comparisons, concrete examples, and visual representations. You may want to take out a meter stick for this first explanation and follow along to help with the visual connection.

• One meter is equal to 100 centimeters; 1 centimeter is 1/100 ^th of a meter also represented as .01m.
• One centimeter is equal to 10 millimeters; 1 millimeter is 1/10 ^th of a centimeter represented as .1cm and 1/1000 ^th of a meter represented as .001m.
• One millimeter is equal to 1000 micrometers; 1 micrometer is 1/1000 ^th of a millimeter represented as .001mm and 1/1000000 ^th of a meter represented as .000001m.
• One micrometer is equal to 1000 nanometers, 1 nanometer is 1/1000 ^th of a micrometer represented as .001m.
• One nanometer is one billionth of a meter or 1/1,000,000,000 ^th of a meter represented as .000000001m.

Relative comparisons may be helpful to grasp the concept of the smallness of the nanoscale. Now I include scientific notation.

• A standard school bus with a length of 12 meters is 12,000,000,000 (12 billion) nanometers long or 1.2 x 10 ¹⁰ nm.
• An average 20 cm long pencil is 200,000,000 (200 million) nanometers long or 2 x 10 ⁸nm. Look at a piece of your hair. A human hair is about 80 micrometers or 8 x 10 ¹m in diameter that translates into 80,000 (80 thousand) nanometers thick or 8 x 10 ⁴nm.
• One inch equals 2.54 centimeters or 2.54 x 10 ⁰cm, 25.4 millimeters or 2.54 x 10 ¹mm, 25,400 micrometers or 2.54 x 10 ⁴m, and 25,400,000 (25 million four hundred thousand) nanometers or 2.54 x 10 ⁷nm.
• A mosquito is about 5mm or 5,000,000 (5 million) nanometers long or 5x10 ⁶ nm.
• The common reddish-brown house ants are approximately 2 to 3 millimeters long or 2 x 10 ⁰ to 3 x 10 ⁰mm, about 2,000 to 3,000 micrometers in length or 2 x 10 ³ to 3 x 10 ³m in length, and nearly 2,000,000 to 3,000,000 (2 to 3 million) nanometers or 2 x 10 ⁶ to 3 x 10 ⁶nm long.
• A red blood cell, the cell that gives our blood color, is approximately 7 micrometers in diameter or 7 x 10 ⁰m, and 7,000 (7 thousand) nanometers in diameter or 7 x 10 ³nm in diameter.
• Many of us dread grains of pollen, particularly during the onset of spring. Pollen grains range in size from 25 to 50 micrometers or 2.5 x 10 ¹ to 5 x 10 ¹m and 2,500 to 5,000 nanometers or 2.5 x 10 ³ to 5 x 10 ³nm. Billions of pollen grains will fit into one teaspoon (can you prove this?).
• Bacteria are abundantly distributed in soil, air, water, in and within the tissues of plants and animals. The diameter of bacteria is usually 1 to 3 micrometers or 1 x 10 ⁰ to 3 x 10 ⁰m and 1,000 to 3,000 nanometers in diameter or 1 x 10 ³ to 3 x 10 ³nm in diameter.
• I think it is safe to say that we have all seen at least one butterfly in our lives. Try to envision how delicate and thin the wings of a butterfly are. Well, some butterfly wings are made up of scales that are each 90 nanometers thick or 9 x 10 ¹nm thick. About one thousand of these butterfly wing scales, stacked on top of each other, would fit across a single human hair.
• The virus that causes the common cold is 20 nanometers in diameter or 2 x 10 ¹nm.
• Many atoms, which are the building blocks of all matter, are smaller than 1 nanometer in diameter. The width of a single water molecule that is made up of two hydrogen atoms and one oxygen atom is one nanometer, pretty minuscule. ²

When we think of particles that are being manipulated on the nanoscale, we are thinking about particles or pieces of matter that are somewhere between the size of a scale on a butterfly wing and a water molecule. (To see the relationship between objects at the different scales identified above, please visit http://learn.genetics.utah.edu/content/begin/cells/scale/. It shows different objects at different magnifications and scales.) A suggested activity to help students understand the smallness of the nanoscale is "Cutting it Down to Nano". This activity can be obtained from http://mrsec.wisc.edu/edetc.

This unit also provides an introduction to the concept of negative exponents. It is represented here simply as the exponential representation of the denominator of a fraction representing division by powers of 10. It may be helpful to refer back to the metric comparisons identified earlier.

• 10 Centimeters = 1/10m = .1m = 10 ^-1m (one tenth of a meter)
• 1 Centimeter = 1/100m = .01m = 10 ^-2m (one hundredth of a meter)
• 1 Millimeter = 1/1000m = .001m = 10 ^-3m (one thousandth of a meter)
• 100 Micrometer = 1/10000m = .0001m = 10 ^-4m (one ten thousandth of a meter)
• 10 Micrometer = 1/100000m = .00001m = 10 ^-5m (one hundred thousandth of a meter)
• 1 Micrometer = 1/1000000m = .000001m = 10 ^-6m (one millionth of a meter)
• 1 Nanometer = 1/1000000000m = .000000001m = 10 ^-9m (one billionth of a meter)