Self Assembly in Nanotechnology

1. Self Assembly in Nanotechnology

2. Self Assembly • Self Assembly is defined as the spontaneous association of numerous individual units of material into well organized, well defined structures without external instruction.

3. The Proposition of Bottom Up Manufacturing • In 1959 Richard Feynman in an address of the American Physical Society proposed that there was plenty of room at the bottom. It was possible to use very small objects to create large objects. • This was the beginning of the idea for nanotechnology and self assembly.

4. Size of Nanotechnology • Nanotechnology involves very small objects. • Objects less than one-billionth of a meter. • The size of a marble compared to the earth. • Building materials for nanotechnology are at the molecular level. www. nisenet.org/publicbeta/articles/think_small/index.html

5. Self Assembly is the Key to Inexpensive Nano-Fabrication • Molecular self assembly has advantages • It is low in cost. • Reduced fuel costs. • Depend on chemical and physical forces to combine materials not petroleum. • Can have high reproducibility. • In nature, materials self assemble with little variation. • Is able to use a variety of materials for creation. • All the building blocks of biology and chemistry.

6. Building at the Nanoscale • Involves a knowledge of many disciplines • Chemistry • Biology • Physics • Electronics • Mathematics

7. Fundamental Knowledge May Need to be Modified • Understanding how the properties of atoms and molecules will vary at such a small scale. • Randomization may play a big role. • Atomic properties may vary at such a small scale.

8. Biology Uses Nanoscale Molecules • Self assembly takes place every day inside your body • Molecules self organize to form structurally defined and stable arrangements. • Cell membranes • Proteins • Enzymes • Cell organelles • To view self assembly in a cell go to: http://multimedia.mcb.harvard.edu/media.html and view the Inner Life video

9. Chemical bonds define physical structure • The angle of the bonds formed between the atoms will define the structure of the substance formed. • Tetrahedral structure of water • Cube structure of salt • Hexagonal structure of carbon-carbon interactions

10. Tetrahedral Structure of Water www.progressivegardens.com/growers_guide/waterstructure.jpg

11. Chemical Forces Organize Self Assembly • Strong Interactions at the chemical level will define some assembly these include • Covalent Bonds • The sharing of electrons between atoms as in water. • Ionic bonds • The formation of charged particles as in salt.

12. Bond Structure www.accessexcellence.org/RC/VL/GG/ecb/covalent_ionic_bonds.html

13. Weak Chemical Interactions • Modify structure within molecules • Organize structure between molecules • Examples include: • Hydrogen bonds • Van der Waals forces • Hydrophobic hydrophilic interactions

14. Hydrogen Bonds • Form when an electron negative atom usually one with more protons than another atom pulls the electrons away from the smaller atom. • Leading to a charge separation with the atom with the most protons having a negative charge and the atom with the least protons having a positive charge. • Most common when hydrogen is bonded to a oxygen, nitrogen or fluorine atom.

15. Hydrogen Bond http://academic.brooklyn.cuny.edu/biology/bio4fv/page/image12.gif

16. Vander Waals Forces • Are weak bonds between molecules caused by the random fluctuations in electrons. • The atoms within the molecules exist as transient dipoles. • One part has a weak negative charge another part a weak positive charge. • Example: water

17. Vander Waals Forces http://www.straightdope.com/mailbag/WaterPolarity.jpg

18. Hydrophilic –Hydrophobic Interactions • Molecules can exist as polar and nonpolar molecules. • Polar molecules have charges and interact with other charged molecules. • NaCl readily dissolves in water another charged molecule. • Nonpolar molecules do not have charges. • Olive oil is an example. • Nonpolar molecules readily dissolve in other nonpolar molecules. • Butter and olive oil will mix. • But do not readily dissolve in polar molecules. • Oil and water do not mix. • This inability to mix leads to structure.

19. Hydrophilic –Hydrophobic Interactions http://www.biologycorner.com/resources/lipidbilayer.gif

20. Forces of Chemical Reactions • Two forces control whether or not reactions will occur spontaneously. • Entropy - the amount of order in a system. • Enthalpy – the energy found in the bonds in the chemical reaction. • Chemical reactions occur spontaneously if the disorder in the system is increased (entropy) and the molecules) formed have less energy then the original molecules (enthalpy).

21. Entropy www-lmmb.ncifcrf.gov/~toms/icons/s.harris-dep...

22. A Non Biological Forces Can Lead to Self Assembly • Magnetism – the power of attraction that exists in materials such as iron. • Ferromagnetism is defined as the state when the relevant electron spins within a material all point in the same direction. • Attraction of a metal to a magnet can lead to a stable structure. • nanotechnologya\V_ H_ Crespi Magnetism @ Penn State Physics.htm

23. Magnetism http://www.teachnet-lab.org/ps101/bglasgold/magnetism/magnetism2.jpg

24. Biological Materials used in Self Assembly • Nanotechnologists are using a variety of biological materials to create nanostructures. • These include: • Carbon based materials such as carbon nanotubes and buckyballs • Proteins – enzymes and antibodies • Lipids • DNA

25. Carbon based Nanostructures • Graphite nanotubes were first discovered in 1991 by Sumio Iijima in Japan. • The carbon atoms in the tubes are arranged in hexagons. • Nanotubes can act as transistors, and pairs of nanotubes can act as logic structures. • They have been added to golf balls, tennis rackets and other materials to increase their strength .

26. Graphite (Carbon Nanotube) • Note the hexagonal structures, each point in the structure is a carbon atom. http://www.nanotech-now.com/images/junction-large.jpg

27. Paper Battery of Nanotubes • In August 2007 at RPI a paper was created using carbon nanotubes. • This paper can extract energy from human blood and sweat. • The battery can be formed into many different shapes and it power increased by adding more sheets of paper • Morgan, R. Amazing Battery made of Paper Discover January 2007 p.51

28. Carbon Nanotube Paper Battery http://www.eurekalert.org/multimedia/pub/4801.php?from=99678

29. Buckyballs • Buckministerfulleren C60 or buckyballs can be created by vaporizing carbon. • It consists of 60 atoms of carbon. • Evidence of this carbon form was first published in 1985 in Nature by Kroto et al. • Their uses include: • reinforcement, adding strength to substances. • Some are being used for drug release in buckysomes.

30. Buckministerfulleren C60 or a Buckyball

31. Buckysome The therapeutic agent attached to the buckysome. http://www.wipo.int/ipdl/IPDL-IMAGES/PCT-IMAGES/21082003/US0304416_21082003_gz_en.x4-b.jpg

32. Nanowire • A nanowire is an extremely thin wire with a diameter on the order of a few nanometers. • Germanium and silicon nanowires can be made. • Function in lithographic printing and silicon chips.

33. Uses of Nanowires • In 2007, orderly arrays of nanowires were grown on crystals in a technique that could lead to high density memory chips and transparent LEDS. • Another use is a detector of cancer. • The conductivity of the wire changes as it binds the cancer proteins. Science News 172:334 http://www.newstarget.com/012956.html

34. Biological Compounds of NanoScience • Proposed Biological Compounds include: • Proteins • Complex structure lets them have specific characteristics and shape. • Lipids • Hydrophilic and hydrophobic interactions permit them to assume specific shapes and to interact with the bodies of cells. • Nucleic Acids • Their specific bonding permits the creation of specific shape and the ability to change that shape under different conditions.

35. Proteins Structure • Proteins are created from amino acids • The 20 amino acids found in nature have unique properties. • Some are acidic some are basic and some are neutral. • Long strings of amino acids form the basic (primary) structure of a protein.

36. General Amino Acid Structure • Variation in the R group leads to acidic and basic and neutral amino acids. Marieb, E. and Hoehn, Human Anatomy and Physiology 7th ed., 2007. Pearson Education, Inc. p. 49

37. Bonds form Chains of Amino Acids • Two amino acids join together in a peptide bond. Marieb, E. and Hoehn, Human Anatomy and Physiology 7th ed., 2007. Pearson Education, Inc. p. 49

38. Protein folding Creates Three Dimensional Structure • Hydrogen bonds between the amino and carboxyl groups creates two main forms of secondary protein structure. • An alpha helix and a beta pleated sheet.

39. Two main primary structures of polypeptide chains. • Two main secondary structures of proteins. Marieb, E. and Hoehn, Human Anatomy and Physiology 7th ed., 2007. Pearson Education, Inc. p. 51

40. Proteins can create Unique Structures • Enzymes and antibodies are unique proteins that because of their specific structure can only attach to other unique structures. • This ability makes them important to nanotechnology because they can be used to bind and cause self assembly by joining together two or more substances.

41. Structure of an Antibody • Three dimensional antibody structure • The antigen binding site is where other substances bind. Marieb, E. and Hoehn, Human Anatomy and Physiology 7th ed., 2007. Pearson Education, Inc. p. 807

42. Functions of Antibodies in Nanoscience • Sensors for biological molecules, bacteria and viruses. The Y shaped structures are the antibodies. http://chemistry.nrl.navy.mil/6170/6177/researchareas.php

43. Molecular Motors • Protein molecules have been investigated as molecular motors. • Three of the proteins that have been studied include: • F1-F0 ATPase an enzyme • Kinesin and dynein • Myosin

44. F1-F0 ATPase • Found in membranes of mitochondria, and chloroplasts in all living organisms. • The enzyme consists of 3 major units the F0 unit, the central stalk that connects the F0 motor to the F1 motor and the F1 motor . • The motor rotates one way during ATP production and the opposite way during ATP hydrolysis or break down. • To view a video on the function and structure of the ATPAse go to: http://multimedia.mcb.harvard.edu/media.html

45. Converting the ATPase to a NanoMotor • Monetemagno’ s group modified the form of the ATPase. • They attached it to a metal surface by modifying its protein structure. • They added a metal rotor so they could observe the rotation.

46. ATPase Motor

47. Animation of ATPase Motor • Molecular Model T Scientific American • http://www.sciam.com/article.cfm?articleID=000988D5-647B-1C75-9B81809EC588EF21

48. Facts About the ATPase Motor • Efficiency of 80 -100%. • Can be turned on and off by adding a zinc binding site and removing zinc from the system. • Relatively short life span. • Could be used to generate electrical current. • Chip based drug delivery pumps. • Step in the right direction but probably not the motor of the future.

49. Kinesin Linear Motor • Moves in discreet steps along microtubules in a specific direction depending on the polarity of the microtubules. • Can be used as a delivery device for the separation, sorting and assembly of materials. • Need to be able to guide the transportation along specific pathways. • Currently using enclosed fluidic channels.

50. Animation of the Motion of Kinesin animation website http://www.fli-leibniz.de/~kboehm/Kinesin.html