Atomic Force Microscope (AFM)

A Lego Project

July 2007

Construction Handout

Construction of the Lego AFM involves creating three structures that will be assemble

into a completed model, a base pedestal, a probe arm assembly, and a laser top assembly .

Bricks of any size, color, or configuration may be used to construct these sub-assemblies. All

bricks are specified in terms of the number of nubs wide by the number of nubs long by the

bricks height (W x L x H). There are only two brick heights, a one unit high and a three unit

high.

Each workstation should have sufficient bricks and green base units to complete the pro-

ject. In addition you should have one laser pointer, one doll house furniture mirror, and a small

quantity of double-sided tape.

Base Construction • Using multiple bricks, construct two pedestals. Each completed pedestal shall be 2 nubs

wide by 6 nubs long by 13 nubs high (hereafter 2x6x13).

• Place the completed pedestals on a green base unit. The pedestals should have 8 nubs be-

tween the pedestals with the 2 nub ends one nub from the long edge of the base unit.

• Locate two individual 2x10x1 pieces and on each of the four ends construct four 2x2x6 tow-

ers.

• Place above unit so that one spans the outer edge of the base pedestals and one spans the

inner edge. There should be a 2x2 space between the units and the outer edge of the pedes-

tals should have an unused row of nubs. See the completed sub-assembly below:

Probe Arm Assembly

• Create the back of the structure by assembling two 2x6x1 bricks held together by a 2x4x1

unit centered on the lower bricks.

• Place the above structure upside down and attach a 1x8x1 piece to each end of the structure.

• To create the probe assembly attach a 1x2x1 centered on the long side of a 2x4x1. To this

unit attach a 1x8x1 to each corner (see picture).

• Create a 2x4x3 brick and place on top of the assembled probe arm (making a sandwich).

• Assemble the probe using a right angle, a 1x3x3 brick, and the white pointer. (see picture)

• Attach the probe unit to the top 2x4x3 brick of the assembled probe arm. (see picture).

• Attach the probe assembly to the Arm Assembly.

.

• Place the finished probe arm assembly into the previously assembled base unit making sure

the probe is pointing down.

Top (laser) Assembly

• Construct two 2x4x6 tower assemblies and place a 4x8x1 unit on top of each tower.

• Construct two 2x4x9 towers assemblies and place on top the above structure.

• Locate the two hinge units and bind them together with a 2x4x1 brick and place the com-

pleted unit centered on top of the second tower. To this add a 2x6x21 brick centered and at

right angles (see picture).

• Place the completed assembly on the base tower assembly with probe arm in place.

Final Assembly

• Place a piece of double sided tape toward the bottom edge of the mirror unit and add a

2x4x1 brick centered on the bottom edge of the mirror.

• Attach mirror over the probe holder. Make sure to align the bottom edge of the mirror with

the back edge of the 2x4x1..

• Place a piece of double sided tape on the 2x6x1 laser holding assembly and attach the laser

pointer.

Basic Assembly is now complete !!!!

Alignment and testing

• Place the completed AFM model so that the probe is 18” from a vertical wall, wood, or

cardboard surface. ( This is an arbitrary distance, but one that keeps the reflected laser point

at a respectable height.) Mark the four corners of the AFM’s platform on the surface so

it can be realigned if it gets moved.

• Place white paper or graph paper on the vertical surface. The paper will need to start ap-

proximately 6” above the bottom of the vertical and extend to create a 24” x 24” square.

• Turn the laser unit on and adjust the angle of the beam so it contacts the mirror at the far-

thest point and still produces a well defined point on the vertical surface. Mark this point

on the paper.

• With the help of your partner, raise the pointer 1/2 inch (It is best to use the edge of the mir-

ror at a point parallel with the probe tip for these measurements) . Mark this point on the

paper.

• Measure between the two marks. You can now calculate the amplification (Magnification)

of the AFM. Record you calculation.

• Using the data from the above, create a scale that extends from the bottom mark up to the

top of the paper.

• Using the second green base unit, 1x(?)x3 strips, and 7 marbles construct the unit as per he

picture below

• Using any number of 2x (?) x 1 bricks, place them so that one edge is on the AFM green

board and one edge is not attached. These should line the edge of the board that has the

AFM probe. (This will make a guide for moving the measured objects.)

• Now place the marbles in position to be measured making sure the two green plates are up

against the guides.

• Turn on the laser and slowly move the base with the marbles. Observe the pattern created

and calculate the height of the peaks and valleys. Record your observation. What can you

tell about the object being measured? What’s missing?

• Move the marble base so that the probe is resting on the top of a marble on one end of the

sequence or the other. Now move the AFM along the guides keeping the marble unit sta-

tionary. What can you now observe about the objects being measured? How would you

calibrate this process? Write a simple procedure for your calibration process.

• Using the skills learned in this project, readjust the AFM and Marble base to measure the

bricks on the outer edge of the green base that retains the marbles. Using only the data pro-

duced by the AFM, describe with measurements and drawings the characteristics of the

measure bricks