Engineering Creativity in Teaching Nanotechnology

Engineering Creativity in Teaching Nanotechnology Mel I. Mendelson Mechanical Engineering Department Loyola Marymount University, Los Angeles, CA

Abstract Various engineering examples of micro-and nano-systems were described with applications in biology, chemistry and electronics. Some 21st Century ethical and social dilemmas were also presented as case studies. Learning was assessed through pre/post-testing and student surveys. Post-testing showed ~ 200% improvement over pre-testing. Student surveys indicated that creating visual drawings, models and real life ethical/social issues improved their learning. Introduction Most of the approaches for teaching nanotechnology have revolved around the basic sciences, i.e., physics, chemistry and biology. This is probably because basic research in nanotech is still evolving. However, there are over 380 products currently on the market that use nanotechnology, and $30 billion worth of nano-products were sold in 2005 1. Scientists are now passing on the development of micro- and nano-systems to engineers for creating new products. Engineers are beginning to design and manufacture micro-/nanosystems. Hence, nanotechnology is taking on an engineering approach. Now nanotechnology is being taught in some engineering departments of U.S. universities, and it requires a different approach when teaching it to engineering students. Since nanotechnology deals with molecular sizes down to one-billionth of a meter (10-9 m), many students have difficulty visualizing molecules in action. Hearing lectures and memorizing scientific concepts was considered an ineffective way of learning the subject 2. Instead experiential learning (learning by doing and by collaborating) was pursued as an improved method of learning. Nanotechnology is taught at Loyola Marymount University (LMU) as an interdisciplinary course for sophomore/junior students in both science and engineering 3. Our course, entitled Introduction to Nanotechnology, has been taught for the last four years at LMU as a primer in nanotechnology concepts. More recently our course has taken on an engineering flavor. The hypothesis for this work was student learning in nanotechnology would be improved by visual illustrations, hands-on activities, and ethical/social dilemmas in nanotech. The purpose of this paper is to discuss a wide range of creative engineering methods that have been used for testing this hypothesis. This paper is divided into sections to illustrate the exercises that were taught and assessed in our course. These sections include: • Design and Construction • Measurements • “Free Body” Forces • Ethics and Social Values

Proceedings of the 2007 American Society for Engineering Education Pacific Southwest Annual Conference Copyright © 2007, American Society for Engineering Education

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Impact on Student Learning

Design and Construction Drawing and building physical models was intended to help students visualize sizes in the microscopic (0.1 – 100 μm) and nanoscopic (1 – 100 nm) regimes. This strategy gave the students an appreciation for molecular assembly from the bottom-up. Models of buckyballs, nanotubes, DNA helix, and DNA tetrahedron were selected for our class. Buckyball construction. Buckyballs were discovered in 1985 by Prof. Smalley at Rice University 4. Buckyball are molecules that contain 60 atoms and are shaped like a soccer ball. These molecules are being considered as biosensors and actuators for treating diseases. The students had to build a 3-D model from a 2-D development. The 2-D development (Figure 1a) was drawn on thick paper, and it was cut out along the perimeter of the hexagons. The 2-D cut-out was folded along its hexagonal lines and taped into a 3-D shape with open pentagons (Figure 1b). Buckyballs consisted of 12 pentagons and of 20 hexagons. The 2-D cut-out purposely omitted the pentagons, so the students to could see through the 3-D assembly. Also, the ‘see through’ buckyballs were assembled with an atom (Styrofoam ball) inside, which was called a ‘caged buckyball.’ The students had to see through the open pentagons in order to suspend the Styrofoam ball inside of it.

(a) (b) Figure 1. (a) 2-D development of hexagons for buckyball, and (b) 3-D construction of buckyball with ‘see through’ pentagons.

Nanotube design and construction. Nanotubes were discovered in the early 1990s 4. They are also a carbon molecule in the form of hexagonal graphite layers that have been rolled up into a hollow cylinder. They are about 500 times stronger than steel, and they are currently being tested in preclinical trials for treating cancer 5.


The students had to draw and build two types of single-walled nanotubes: arm chair and zigzag (Figure 2). The students started by drawing two different hexagonal carbon orientations (arm chair and zigzag) on flat plastic transparencies. These transparencies were rolled-up and taped into hollow cylinders to simulate the way nanotubes form from graphite layers. The transparencies were held on an overhead projector so the cylindrical structures could be seen by transmitted light. The zigzag transparency was twisted to form a chiral nanotube (Figure 2).

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Figure 2. Photograph of three different nanotubes – armchair, zigzag and chiral .

DNA helical structure. DNA is a molecule that provides the blueprint of life. It consists of phosphorous and sugar double helix that is bonded together by base-pairs (Figure 3b). The sequencing of the base-pairs distinguishes different biological organisms 6. To illustrate the four combinations of base-pairs, four different colors were used to construct the DNA molecule from the bottom-up (Figure 3a), where G – C = ‘blue’ base pairs, C – G = ‘red,’ T – A = ‘white,’ and A – T = ‘black.’ A – T C – G T – A T – A A – T T – A T – A C – G G – C G – C G – C G – C (a) (b) Figure 3. (a) Photograph of DNA model using Lego blocks. (b) DNA base-pairs for helical DNA.


The DNA spiral staircase model was constructed using Lego blocks and popsicle sticks (not shown). Each student was given 80-100 popsicle sticks and instructions on how to assemble them into a DNA molecule with helical structure. This was a very inexpensive way to build a DNA molecule. It was at least 10 – 100 times cheaper than current models on the market. DNA tetrahedron. DNA molecules have been cross-linked to form different geometrical structures, which were discovered around 2005. These structures are being considered for carrying and delivering drugs into cells. The students had to build double helix structure in the form of a tetrahedron out of 50 mm diameter Styrofoam balls and tooth picks (Figure 4). Each Styrofoam ball represented one-half helical turn of DNA. After the tetrahedron was assembled, the students had to draw the helical DNA structure on the balls.

Figure 4. DNA tetrahedron, where balls represent one-half helical turn of DNA molecule.

Measurements Measuring the size of various objects was intended to give the students an appreciation for the relationship between the different size regimes – macroscopic, microscopic and nanoscopic. The scanning electron microscope was used due to its high depth of focus in imaging 3-D features. Scanning electron microscope (SEM) measurements. The students observed sugar granules, the micro-lens and eye of a mosquito, and a transistor. The edge length of sugar cubes was determined, and then the number of molecules in the granules length were calculated if the sugar molecule was 1 nm long. The students measured the diameters of the mosquito’s micro-lens and eye, and they estimated the number of micro-lenses in the mosquito’s eye (Figure 5a). Next a 3-D model was constructed of a field effect transistor (FET) switch, so the students could see it from the top and cross-sectional views and visualize how it was fabricated from the top-down. An illustration of the transistor’s cross-section is used in this paper (Figure 5b). The length of an FET switch was measured on a 5 mm square chip, and then the number of transistors on the chip could be estimated. Nail and hair growth. Each day in class, the students would measure their right thumb nail with


Transistor Length

(a) (b) Figure 5. (a) SEM photograph of the eye of a mosquito 7. (b) Schematic cross-section of transistor 8.

Vernier calipers over a one-month period. Their nail growth was determined to be linear with time, ranging from 0.5 – 1 nm/s (Figure 6a) 9. The nail growth rate was correlated with forming 3 – 7 amino acid molecules per second. This process was repeated on the growth of a male student’s beard (Figure 6b). The growth rate was linear and about 4x faster than thumb nails. Hair Growth Rate 12 10 R2 = 0.993

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Length (mm)

Nail Growth (mm)

Nail Growth vs. Time 3.5 3 2.5 2 1.5 1 0.5 0 -0.5 0

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R = 0.983

6 4 2

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R = 0.988

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20

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40

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35

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Time (days)

(a) Figure 6. (a) Thumb nail growth vs. time. (b) Hair growth vs. time.

Day

(b)

“Free Body” Forces Every engineering student must be able to balance forces and moments on an object in static equilibrium. An experiment was first performed by placing 0.5 mm diameter pencil leads in a glass of water. The leads were placed both horizontally and vertically on the water. In both cases the leads were supported on top of the water and did not sink. When a surfactant (e.g., soap) was added to the water, both leads sunk to the bottom of the container. The students were asked to explain the results in terms of the size (and weight) of the object and the forces acting on it, as shown in Figure 7.


(a)

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Figure 7. (a) Forces acting on a cube (of size ‘d’) in water, where FG = gravitational force, FB = buoyancy force, and FS = surface tension 10. (b) Mosquito walking on water 11.

Another experiment was performed in class. The students had to explain the forces acting on the three types of liquid molecules – cohesive force on surface molecules, cohesive forces of bulk molecules, adhesive forces of surface molecules. These are shown in Figure 8.

(a) (b) Figure 8. (a) Illustration of liquid molecules (O) on the surface and in the bulk with cohesive forces acting on the ‘black O’ molecules 12. (b) Illustration of adhesive and cohesive forces acting on ‘green’ molecule in meniscus, where ‘blue O’ = molecules of wall, and ‘white O’ = liquid molecules.

Ethics and Social Values Engineering ethics and social values has been defined as the study of the moral values, issues and decisions involved in engineering practice 13. Throughout our course, current newspaper and journal articles were used to introduce a particular problem or issue in nanotechnology. Then the students were given a ‘case study’ that involved 21st Century ethical dilemmas in nanotechnology. The case studies that were used in the course were as follows: • Consequences of extending human life (to 150 years) through nanotech drugs • Helpful vs. harmful effects of nanotechnology, and possible toxicity issues. • When a disease-curing nanotech drug is available in short supply, who should get the drug? Who should decide who will get it?


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Effects of DNA profiling and personalized medicine Implications of nano-particles in the air, clean rooms, and hospital operating rooms

The students had to explain both sides of the issue in a position paper. Then they had to write a ‘position paper,’ where they took a position on the case study. They had to explain their position based upon the based upon the IEEE engineering code of ethics 14. Afterwards, the ethical and social issues of case studies were discussed and debated. Impact on Student Learning In order to test the hypothesis that student learning would be improved, student learning was assessed in two ways: • Pre-test / post-test evaluation • Student learning survey Pre-test/post-test evaluation. The difference between the post-test and pre-test results was assumed to be an indicator of the degree to which our students grasped the basic concepts. At the start of the nanotechnology course, students were given a ‘pre-test’ that consisted of ten questions, which were representative of the course material. The same test was given to the students at the end of the course, which was called a ‘post-test.’ The average score of the students on the pre-test was 23%. For the post-test, the average score was 70%. The average scores increased by a factor of 3, which indicated a 200% improvement. The results implied the students had a better understanding of nanotechnology concepts after taking our course than before our course. Student learning survey. Using a Likert scale (1 – 5 scoring system) 15, the students had to answer questions were scored as: 5 = strongly agree, 4 = agree, 3 = maybe, 2 = disagree, and 1 = strongly disagree. There were three questions that the students answered in a survey to test our hypothesis. The questions were as follows: (1) Visual drawings helped you learn nanotechnology. (2) Hands-on molecular models improved your learning of nanotechnology. (3) Real life ethical and social issues were beneficial in understanding the dilemmas of nanotechnology. Table I. Average Score of Student Survey Paraphrased Questions in Student Survey

Average Score

1. Visual drawings models helped you learn nanotech.

4.2

2. Hands-on molecular models improved your learning.

4.4

3. Real life ethical & social issues were beneficial.

4.1

The average scores indicated the students agreed that drawings, models and ethical/social issues were beneficial in learning about nanotechnology.


Conclusions • •

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The teaching hypothesis was student learning would be improved using different participative activities relating to nanotechnology. Several hands-on activities were used in the classroom – designing and constructing nano-molecules (buckyballs, nanotubes, DNA, DNA tetrahedron), measuring the size of different objects (sugar cubes, micro-lens/eye of a mosquito, a transistor, finger nail and hair growth, forces on different bodies), writing and discussing various 21st Century ethical/social dilemmas. Pre/post-testing indicated that student learning had increased three-fold, and surveying the students showed that they ‘agreed’ with the hypothesis.

References 1. M2 Communications, “Yale University: Study at Yale finds emotions and values shape how people think about nanotechnology,” Small Times, March 8, 2007. 2. R. Felder, J. Stice, National Institute for Effective Teaching, 3-Day Workshop, American Society for Engineering Education (ASEE), 2000. 3. M. Mendelson, “Initial Lessons Learned in Teaching Nanotechnology to College Sophomores,” 2005 ASEE Pacific Southwest Regional Conference, Loyola Marymount University, Los Angeles, CA, April 7-8. 4. “Nanotechnology / Carbon Nanotubes,” Small Tech 101: An Introduction to Micro and Nanotechnology, Small Times, p. 22, 2003. 5. R. Booker and E. Boysen, Nanotechnology for Dummies, Wiley Publishing, Inc., Hoboken, NJ, 2005. 6. I.E. Alcoma, DNA Technology: The Awesome Skill, 2nd ed., Harcourt Academic Press, San Diego, CA, 2001. 7. Mosquito’s eye, http://www.mos.org/sln/sem/intro.html. 8. J.J. Brophy, Basic Electronics for Scientists, 3rd edition, p. 148, McGraw-Hill, New York, 1977. 9. M. Mendelson, “Molecular Bio-Nanotechnology Experiment in the Classroom,” 87th Annual Meeting of the American Association for the Advancement of Science (AAAS), Pacific Division, Proceedings Vol. 25, pp. 44, 80, University of San Diego, CA, June 18-22, 2006. 10. Sandia National Laboratories, http://www.mems.sandia.gov. 11. T.A. McMahon, J.T. Bonner, On Size and Life, p. 39, Scientific American Books, Inc., New York, 1983. 12. W.J. Moore, Physical Chemistry, 2nd edition, p. 498, Prentice-Hall, Inc. Englewood Cliffs, NJ, 1960. 13. M.W. Martin, R. Schinzinger, Ethics in Engineering, 2nd edition, McGraw-Hill, New York, 1989. 14. IEEE Code of Ethics, http://www.ieee.org/about/whatis/code.xml. 15. Likert scale, http://en.wikipedia.org/wiki/Likert_scale.
