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Nanotechnology in Biology

Louie A. Baca, Jr. and Eric Hagedorn

http://www.egr.msu.edu/liao/BE825/lecture22.pdf

http://www.engr.sjsu.edu/MatE129/Continuing%20Ed/Etching/Etching

.pdf

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Size and Measurement (Overview)

Thought probing questionsasked to students tointroduce upcoming topic

Examples:

What is nano?

What is a nanometer? How small is a nanometer?

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Size and Measurement Overview

Lecture: cell and cell

structure introduction of new

concepts/awaken priorknowledge

This lesson follows chapteron measurements in thedistricts scope and sequence

Students paired for size andsort activity (size predictionsmade)

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Activity 1: ´How Small Am I?µ

Set of ten cards given to

students dealing with cellstructure as well as geneticmaterial and individualorganisms

Examples: nucleus, virus, DNAstrand, ribosomes, endoplasmicreticulum, eukaryotic cell, etc.

Students will then putobjects in order fromsmallest to largest and recordanswers on data sheet

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Activity 1: Continued

Relative size will then be

determined given a standard tocompare to

Example: compare the size of five ofthe structures to that of the cellsnucleus (relative size provided)

Results will be recorded in datasheet

Lecture following activity to

introduce how nano-sized objectsare measured (intro intomicroscopes and microscopy)

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Nanotechnology Nanotechnology is the manipulation of

matter at a scale of 1 to 100 nanometers.

Using nanotechnology we can controlmolecules at an atomic level and creatematerials with unique properties.

A nanometer is 10-9 (a billionth) of ameter. The prefix nano is Greek fordwarf.

As a reference point, a hair isapproximately 100,000 nanometers.

A red blood cell is approximately 10,000

nanometers. See diagram on the following slice and

images from www.nbtc.cornell.edu,www.denniskunkel.com, andhttp://www.nanohub.org/resources/?id=90

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Why is nanotechnology so important?

Fundamentally the properties ofmaterials can be changed bynanotechnology.

We can arrange molecules in away that they do not normallyoccur in nature.

The material strength,electronic and opticalproperties of materials can allbe altered usingnanotechnology.

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Manipulating Matter at the Nanoscale

Three methods

1. Pick them up and

move them

2. Pattern them

(lithography)

3. Use self-assembly

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1. Pick Them Up

The tip of an AFM can be used to move a moleculeif you can figure out how to pick up and thenrelease the molecule.

This is one of the more famous real images of

nanotechnology.In the mid-1980s, IBM spelled their logo using

thirteen xenon atoms. Each atom was pickedup using an AFM tip and moved into place.

While the picture suggests a very nice stablearrangement the atoms were in factcontinuously moving and the letters were

short lived.

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WHAT IS THIS FIGURE?

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2. Lithography

All nanometer sized electroniccomponents are made using a processcalled lithography.

Alois Senefelder of Munich discovered thebasic principle of lithography, printingon stone, around 1798.

It is based upon the notion that oil andwater do not mix.

Photolithography involves using energy(e.g., light or electrons) to change thesolubility of a material.

Photolithography literally means light-

stone-writing in Greek. An image can be produced on a surface

by drawing with light or electrons muchthe same way that you might scratchaway the crayon on a scratch board

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Activities

Patterns can be made on a surfaceby drawing with an oily substance(like a crayon), and only wherethe oily substance is not presentwill a water-based ink adhere.

You can also cover the entiresurface scribbling with a crayonand then scratch away to drawyour pattern. Craft people call this

type of material scratch boards. The key in nanotechnology is to

draw with very fine resolution.

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Activities 1. Ask if any students have a mechanical

pencil or a pen that has a specified line width.

The finest mechanical pencils draw a line that is0.5 millimeters. That is 500 microns or about1,000 times wider than the wires inside of acomputer chip.

2. Ask the students to think of some processthat involves light and causes a chemicalchange. sun tanning photography. Both involve a chemical that is

changed by exposure to light.

3. Ask students to think about how both suntanning and photography work and discussthe differences. Both involve a chemical change that is

triggered by light.

sun tanning, the light is mostly ultraviolet andthe reaction involves cells that are stimulatedby sun light producing a pigment. The pigment,melanin, is produced to protect cells againstdamage due to sunlight.

In photography, tiny silver crystals in the filmare reactive to different wavelengths of visiblelight and produce the variety of colors

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Back to nanotechnology and photolithography

In nanotechnology we usephotolithography to transfer a pattern

from a mask to a surface. We apply a special chemical called

photoresist, which is sensitive to light,onto the surface that we want to pattern.

The mask is a stencil which allows the

light energy to pass through only certainregions. So a pattern on a mask can betransferred to a surface by passing lightor electrons through the mask.

When the light or the electrons reach thephotoresist on the surface, the solubility

of the photoresist changes making iteasier or harder to wash away.

What is left after washing is the three-dimensional pattern that was originallyon the mask.

It is transferred to the photoresist.

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Photolithography

Scientists use photolithography tomake computer chips and otherdevices that have very smallfeatures, as small as 100

nanometers.

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3. Self-assembly

Molecules self-assemble when

the forces between thesemolecules are sufficient toovercome entropy. Entropy iswhat drives molecules to alow energy state.

Ask students to think of anexample where moleculesarrange themselves into apattern. Snow flakes

Salt crystals

Soap bubbles

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Snowflakes and Salt Crystals

Snowflakes form around nanoscale

particles of dirt that nucleate ice crystals.As the temperature approaches thefreezing point of water, the hydrogenbonds between water molecules arrangethe water into a crystal pattern thatgrows.

Salt will assemble to form crystals. Saltcrystals form as the salt moleculesarrange themselves while the waterevaporates. The bonds between the saltmolecules are strong enough to squeezeout the water and arrange themselves to

form a crystal. The different geometriesof the salt molecules affect the shape ofthe salt crystals, so the nanoscalegeometry affects the macroscaleappearance of the crystal.

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Soap Bubbles

Soap bubbles self-assemble. The soapmolecules form two layers that sandwicha layer of water in between. This isbecause the soap molecules have one endthat likes water and one that does not.So the end that does not like water is on

the outside and the other end that likesthe water is on the inside. The soap formsa monolayer on the inside and amonolayer on the outside of the water.Each layer of soap is a self-assembledmonolayer, a single layer of moleculesoriented in one direction. It is also

flexible, which results in changes in theappearance (e.g., color, reflectivity) ofthe soap bubble.

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Self Assembly activity

Have students blow a soap bubbleand observe it.

Why do the colors look like a rainbow?

White light is composed of all the visiblecolors. The light passing through thebubble creates a phenomenon calledinterference. The colors in a bubble appearbecause light is reflected from both theinside and the outside of the bubble at thesame time. The bubble is so thin that thelight reflected from the outside is eitherenhanced or canceled out by the lightreflected from the inside. When the twosets of reflected waves are combined, they

can remove or reinforce variouswavelengths of light thus enhancing somecolors and suppressing others.

All of this happens because the distancebetween the outer and inner layer of thebubble is approximately 150 nanometers,about 1/1,000 the width of a hair.

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Schematic of Soap Bubble

Figure 7. Soap bubble schematic,home.earthlink.net/~marutgers/science/soapbasics/gifs/bubble.gif