mass energy review, applications of interference, holographic optical tweezers, lithography, introduction to mechanics and Newton's laws

1. Today: Interference topics, intro to mechanics Exam #3 is Thursday! 1/3 millimeter Electron Microscope Image of MEMS Force Sensor

2. Quiz 10 (Which has more mass?)

3. Quiz 10 (Which has more mass?) A carbon nucleus is stable / has significant “binding energy”

4. Protons and neutrons weigh LESS when bound together! More decrease in mass + 0 + + + 0 + + 0 0 0 0 Carbon-12 nucleus, Mass = 12 u (by definition) + 0 Single free proton Mass = 1.007825 u Single free neutron Mass = 1.008665 u You need to ADD energy to take apart a C-12 nucleus

7. Protons and neutrons weigh LESS when bound together! More decrease in mass Very significant energy release by fusion of deuterium / tritium

10. Immediately, Nuclear Fusion was recognized as an even greater source of energy And of course, hydrogen is a very abundant element!

11. Remember to study quizzes for exam! One topic that we will cover is diffraction and interference of light. Let’s review a little by looking at applications.

12. Laser Diffraction Demo (Repeat) Laser Lens Diffraction Grating Lens Interference pattern on wall Laser Light

16. Holographic Optical Tweezers for Biology Laser Lens PROGRAMMABLE Diffraction Grating (e.g. LCD) To Microscope, Creating optical tweezers Changing deflection of laser beams

17. You know more physics now about optical tweezers

18. You know more physics now about optical tweezers Focused laser beam Light has momentum! Small plastic bead a little lens! If bead moves left, laser is refracted left equal and opposite force on bead to the right If bead moves right, laser is refracted right equal and opposite force on bead to the left Newton’s third law: every force has an equal force in the opposite direction Arthur La Porta, U. Maryland

19. Can “unzip” DNA double helix with optical tweezers! Requires about 15 piconewtons to unzip DNA This is less than one trillionth the force required to lift your body! (About 1,000 Newtons) 3 “microns” F F 1 2 . . . j

20. Can “unzip” DNA double helix with optical tweezers! Using optical tweezers, we can find where proteins are along a single DNA molecule! Our lab is currently working to unzip DNA molecules extracted from living cells! With protein Without protein Protein F F 1 2 . . . j

21. Brainstorming exercise What are possible uses of optical tweezers?

22. “ Knitting DNA” http://www.youtube.com/watch?v=v97MesU3Zkw&feature=related Video game http://www.youtube.com/watch?v=jCdnBmQZ6_s&feature=related

23. You also have learned physics relevant to the microelectronics industry Photons have energy & can catalyze chemistry Diffraction effects—diffraction limits how small we can go Interference effects

25. Smaller features = better computer Limited by diffraction of light! Original Mask Tolerable Diffraction Too much diffraction

26. Interferometric Lithography at UNM (CHTM) Porous nanochannels made by CHTM folks These are about 500 nm nano channels (edge-on), whose walls are made of silica nanoparticles, and thus porous. These bright dots are images of lambda DNA in CHTM porous nanochannels. The channels are too big (>500 nm) to stretch them out. Brueck group, CHTM Fluorescent DNA in nanochannels

30. We are using MEMS for biophysics applications -> Measuring tiny forces 1/3 millimeter Electron Microscope Image of MEMS Force Sensor

32. We used the tiny spring to weigh tiny things 30 micron plastic beads Weight = 100 piconewtons Typical human hair for comparison Force = k * spring displacement k = 1 piconewton per nanometer

33. We used the tiny spring to weigh tiny things Direction of gravity Force = k * spring displacement k = 1 piconewton per nanometer

43. Lecture ended here (after F=ma video)