# 3.052 Nanomechanics of Materials and Biomaterials Assignment #4 Due

Save this PDF as:

Size: px
Start display at page:

Download "3.052 Nanomechanics of Materials and Biomaterials Assignment #4 Due"

## Transcription

2 where D o is the equilibrium separation distance for hard wall contact and D c is the critical distance from the bottom of the spatula pad at x 1 to the bottom of the spatula pad at x 2. From geometry one obtains eq. [11] of Tian, et al. for D c ; D = R (1 -cosθ) [3] c where R = the radius of the spatula (which will be set equal to the radius of the cylinder) and θ = the spatula bend angle. Hence, when θ =0, D c =0, D=D o. However, this relationship doesn t hold for small θ, so the authors used an empirical power law (Eq. [12] to relate R and θ: R = 4125θ 1.35 [4] Substituting [4] into [3] and [3] into [2] one obtains: Substituting [4] and [5] into [1] one obtains : D = D θ 1.35 (1 - cos θ ) [5] o Αb (4215θ 1.35 ) 0.5 F vdw = 16 2 [D0 + (4215θ 1.35 )(1 cosθ )] 2.5 [6] As given in the paper, the Hamaker constant A = 0.4 x J, D 0 = 0.3 nm, and b = 200 nm. Use these values in equation [6] to calculate F vdw ( θ ) for θ from 0 o to 90 o, and plot F vdw (θ ) / F vdw (90 o ) vs. θ to recreate Figure 4. Figure 4 Fvdw/FvdW(90) theta [degrees] See the Excel file posted on the MIT Server for graphing details. b. How do Figures 5 and 6 explain the roll-in, roll-out mechanism for gecko walking? Figure 6 shows that F n and F L are highest at low angles, so that the gecko rolls in to low angles, less than 30 o, to attach strongly in both friction and adhesion. Figure 5 shows that F(θ), 2

3 the force at which the gecko needs to pull its toes in order to detach from the surface, is lowest at high angles. The gecko rolls out to raise the attachment angle up to 90 o, where it is easy for it to pull hard enough to overcome the attachment forces due to friction and adhesion, and pull away from the surface. c.from the Discovery Channel movie on Professor Autumn Kellar i. Explain what was meant by "the gecko hairs become one with the wall." The molecular origin of van der Waals forces is the polarizability of electron clouds of gecko foot atoms with the electron clouds of wall atoms inducing an instantaneous fluctuating dipole which causes an attractive force, essentially causing the gecko foot hairs to "merge" at the atomic level with the wall. ii. Explain what was meant by "the gecko is the Bermuda triangle of biology." This phrase refers to the fact that many different theories have been proposed for gecko adhesion, and that if a scientist were to study one area he/she could get sucked up into a black hole of research and not make any significant progress. iii. Name a number of potential applications for the fundamentals behind gecko feet adhesion. Several potential applications were mentioned in the Discovery Channel video and some are listed here. However, there are potential many more great applications for gecko-like adhesive mechanisms. - climbing aids ( gecko gloves ) - removable adhesives ( gecko tape ) - search and rescue robots which climb & crawl like geckos - Mars gecko rovers - Children s toys iv. What is the "Mecko Gecko"? The Mecko Gecko is a robot with sticky feet. The feet do not adhere by van der Waals forces like the gecko, but the robot overall uses some of the same walking principles as the gecko. v. Name 3 other types of biological adhesion mechanisms and the animals that use them. - Secreted biomacromolecular adhesives used by different bugs - Capillary adhesion used by frogs - Suction used by salamanders - Ligand-receptor lock-and-key cell adhesion 2. Boundary Lubrication Podcast: Briscoe, et al., Boundary Lubrication Under Water. Nature 444, 9 November 2006, a. Research 3 different definitions of "boundary lubrication" and 3 different technological applications where boundary lubrication is relevant (cite all sources). 3

4 There are several different definitions for boundary lubrication ; the differences largely stem from the scale of the technological application where the lubrication is relevant. Following is a sampling of definitions chosen at random from solutions submitted by students taking this semester: Definitions of boundary lubrication -- the reduction of friction and wear between rubbing surfaces with molecular monolayers on the surfaces (Briscoe, et al., Nature 444, 2006: submitted by Amanda Morris) -- When a complete fluid film does not develop between two rubbing surfaces, boundary lubrication is necessary to reduce the friction between the surfaces. Because of this non-uniform fluid film, the thickness may be thinner in some regions compared to others which allow dry contact between the wear surfaces. Basic mineral oil is used to create a lubricant that forms a surface film over the surfaces. The most common boundary lubricants are different types of greases because they have the most desirable properties. They not only shear easily but they also flow and dissipate heat easily, and form a protective barrier for the surfaces. ( submitted by Kimberly Kam) -- that condition of lubrication in which the friction between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity. Boundary lubrication encompasses a significant portion of lubrication phenomena and commonly occurs during the starting and stopping of machines. (Encyclopedia Britannica: submitted by Katrine Siversten) Technological applications relevant to boundary lubrication: -- Boundary Lubrication is found in vivo in many places, in the body, between the lungs and the chest walls for example. This paper (Hill, B.A., Boundary lubrication in vivo, Proc Instn Mech Engrs 214(H):83-94, 2000; is a summary of boundary lubrication in vivo. The information from this paper can be used to develop better implants and prosthetics, such as in the second source, where it is applied for making artificial joints.( ) (submitted by Siamrut Patanavanich). -- Boundary lubrication is important to the design of mechanical ball bearings between moving parts in many types of machinery. ( oundary+lubrication%22+technological+applications&ots=zm- KO3CAv9&sig=dolY0eR6qpyzZoGJw4ff0NDCPO0 : book link submitted by Elaine Lee) -- Boundary lubrication is important most machines during startup and shutdown. This is the case with piston rings in engines. Teeth and saliva are another example. The barrel of gun needs to be oiled for the bullet. ( rication.pdf) (submitted by Fredrick Porter). Professor Klein proposes that ions can behave as "molecular ball bearings" in boundary lubrication. Explain this analogy. Ions in solution are surrounded by water molecules in a hydration layer. It takes a great amount of energy to remove this hydration layer, but it is believed that water molecules within the hydration layer can very easily exchange with each other for very little energetic cost. This 4

5 means that hydrated ions create large normal repulsive forces between surfaces but can actually be very fluid in shear, leading to low shear forces. In this way they act as molecular ball bearings. b. Prof. Klein mentioned that "one can not take pictures with the SFA" (like the AFM can). In a few sentences, explain why not. One cannot image with the SFA because the SFA involves two crossed cylinder surfaces (radius of ~1 cm each) interacting with each other rather than one surface and one very small probe tip as in the AFM. It is the small size of the AFM probe which enables imaging. Interactions measured in the SFA are averaged over the entire contact area, which is generally around 1000 µm 2. c. Professor Klein states that "experiments are meaningless without controls" and refers us to Figure 1 which is a control experiment. Explain in ~0.5 page what these data show and exactly how they verify the accuracy of their experimental setup. Courtesy of Jacob Klein. Used with permission. Source: Briscoe, W. H., et al. "Boundary Lubrication Under Water." Nature 444 (November 9, 2006): The data in the inset of figure 1 show the expected interactions for bare mica surfaces interacting with each other. The data should be well described by DLVO theory, which accounts for the two forces at play: a repulsive electrostatic force due to negative charges on the mica surface, and an attractive van der Waals force. As the theoretical DLVO curves do fit the data quite well, the authors had confirmation of the expected behavior of the SFA under known conditions and could use such such knowledge as a control for experiments with surfactant-coated surfaces. d. The bare mica data from Figure 1 has been digitized and is posted on the MIT Server in an Excel file. Given the theoretical parameters provided in the Figure caption, estimate a 5

6 quantitative value of the Hamaker constant using two separate DLVO theoretical predictions; 1) constant surface charge and 2) constant surface potential. Include in your solutions a single plot showing the theoretical fits compared to the experimental data. DLVO theory combines contributions to interaction potentials stemming from both electrostatics and van der Waals interactions: F DLVO (D)= F EDL (D)+ F vdw (D) First, define the van der Waals portion of the equation. In Lecture 11, page 6, the van der Waals Α R 1 R 2 interaction between two crossed cylinders is given as: W (D)= 6D Differentiating gives the force between crossed cylinders: F(D) = 1 W (D) = Α R 1 R 2 = Α R R D 6D 2 R 6D 2 R = R 1 = R 2 ~ 1 cm (see Figure 1 caption). Hamaker constant = Α = π 2 Cρ 2 ~10-19 J (typical value) The electrostatic double layer contribution can be estimated using two different boundary conditions for crossed cylinders. Using a linearized Poisson-Boltzmann formulation, both can be expressed as F = κrze κd, where the prefactor Z depends on the boundary condition chosen. For a constant surface potential ψ 0, (see Slide 3 of Lecture 16) Z = 9.38 x tanh 2 (ψ 0 /107) [=] J. m -1 ; ψ 0 is in mv From the Figure 1 caption, ψ 0 = 155 mv. This is above the accepted threshold (60 mv) for linearizing the Poisson-Boltzmann formulation, so our fits may not be as accurate as those made in the paper using the full non-linear solution. For ψ 0 = 155 mv, Z ψ0 = 9.38 x J. m -1 * tanh 2 (155/107) = 7.52 x J. m -1. For a constant surface charge σ, Z must be converted according to the following equation relating σ and ψ 0 (also from Lecture 16, slide 3): σ = sinh(ψ 0 /53.4) c 0 [=] C. m -2 ; c 0 is in moles/l. σ Rearranging gives ψ 0 = 53.4arcsin h σ = 53.4 ln σ + +1 c c c Plugging into the equation for Z gives the following equation for Z at constant surface charge σ: 53.4 Z σ = ( J m 1 ) tanh 2 ln σ c 0 + σ c 0 +1 where c 0 units are moles/l and σ units are C. m -2. From the Figure 1 caption, σ = C. m -2 and c o = 1.5 x 10-5 M. This gives Z σ = x J. m -1. 6

7 The Debye length, κ -1, is determined by the properties of the solution in which the experiments are performed, which is noted in the caption of Figure 1 to contain 1.5 x 10-5 M 1:1 background electrolyte. This defines the Debye length as κ -1 = 0.304/[NaCl] 0.5 = 0.304/(1.5 x 10-5 ) 0.5 = 78.5 nm. The full curves are then described by the formula F DLVO = κze κd R 6D The given κ and Z will not give a good fit to the experimental data, since, as noted above, the surface potential is above the threshold for acceptable linearization. However, it is possible to achieve good fits by leaving both the Debye length and the Hamaker constant as free fitting parameters. This was done in the attached Excel file to achieve the following fits: Constant surface potential: ψ 0 = 155 mv; A = J; κ -1 = 28 nm Α 2 Constant Surface Potential F [μ N] D [nm] Constant surface charge: σ = C. m -2 ; A = J; κ -1 = 24 nm 7

8 Constant Surface Charge F [μ N] D [nm] e. The boundary lubrication mechanism presented in the current paper differs slightly from that proposed in Klein's previous paper on fluidity of bound hydrated ionic layers (Raviv, et al Science). Explain how. In the case of boundary lubrication in this paper, it appears that water molecules (probably only two molecular layers thick) have slipped in between the polar headgroups of the amphiphilic detergent molecules involved and the mica surface and that the hydrated ions are fixed and fairly immobile via ionic interactions with the substrate. In the current paper, Klein proposes that the slip plane is between the hydrated polar head groups and the mica surface. 3. The Electrostatic Double Layer / Cartilage Podcast: Dean, et al. Compressive Nanomechanics of Opposing Aggrecan Macromolecules J. Biomech , a. For Figure 6a and b, why isn't the constant compliance regime set to D=0? Explain how this nonzero distance of the constant compliance regime is determined experimentally in <0.5 pages. The constant compliance regime is not set to D=0 because the distance where constant compliance is reached depends upon the structure of the aggrecan layers at each different ionic strength. In the experiments, Dean et al. used AFM height images to measure the compressed height of the aggrecan layers at the maximum force applied in the force-distance measurements; they treated this height as the non-zero constant compliance offset. b. For Figures 6a and b calculate the distance at which repulsion due to conformational entropy begins for each salt concentration and summarize these values in a table. Compare the values obtained in the table for Figures 6a and 6b and explain any differences. 8

9 Repulsion due to conformational entropy can only come into play when the aggrecan layers actually come into physical contact with each other. This would occur a 2 the uncompressed (zero force) height of the aggrecan layer, h o for a single aggrecan layer and 2h o for two opposing aggrecan layers, which would be dependent on salt concentration). These values can be approximated as the total range of interaction, which is equal to the distance at which force rises above noise (D r ) minus the range of the electrostatic double layer (5κ -1 ), as tabulated below. Debye length = κ -1 = / [NaCl] 0.5 [=] nm when [NaCl] is in moles/l. (This equation was given in recitation; it comes from the Israelachvili text and is just the result of calculating εrt κ 1 = for the parameters specific to [NaCl]. ) 2F 2 c 0 Figure 6a Figure 6b., Ionic Strength κ -1 D r h o =D r -5κ -1 D r 2h o =D r -5κ -1 [NaCl] M M M M c. Given the chemical structure and dimensions of aggrecan and GAG and the aggrecan molecular surface packing density reported in the paper, estimate the areal surface charge per unit area (C/m 2 ) due to the GAGs at ph 5.6 (the ph at which the nanomechanical experiments were carried out). ANS. The packing density of aggrecan on planar substrates was cited in the paper (page 2557) as ~ 1 aggrecan per 25 nm x 25 nm area = 625 x m 2. One aggrecan is made up of ~ 100 GAGs attached covalently to a core protein, where each GAG has about 100 negative charge groups, as can be seen from the structure given in Lecture 16, slide 5: GAGs are about 45 nm in length, which corresponds to ~ 50 disaccharides, each of which carries a -2 charge at ph 5.6 (since ph 5.6 is well above the pka of the carboxyl and sulfate groups on the GAG molecule). This means each GAG chain carries a negative charge of around At 100 GAGs per aggrecan, this is charge per aggrecan. One charge carries x C (charge on an electron). From the total charge on all 100 GAGs per aggrecan, and the area per aggrecan, we can calculate the charge per unit area: Areal surface charge due to GAGs = σ 1 = C / aggrecan C / m (25 10 ) m / aggrecan d. Given the known amino acid sequence of the protein core backbone and the aggrecan molecular surface packing density reported in the paper, estimate the areal surface charge per unit area (C/m 2 ) due to the core protein at ph 5.6 (the ph at which the nanomechanical experiments were carried out). You may want to prepare a Matlab script to assist in the calculation. What is the percentage contribution to the total areal surface charge per unit area? 9

10 Based on the chemical structure of the 20 amino acids, the possible charged amino acids at ph = 5.6 are (assuming a particular amino acid is charged when ph pi 2 ) Amino Acids Counts pi Charge Ala (A) Asp (D) Glu (E) Lys (K) Arg (R) His (H) /1 The known sequence of the aggrecan core protein, available from the Swiss Protein Data Bank ( ), and linked from the Nanonewton webpage citation on aggrecan ( ), gives us the number of charged residues within the core protein. You can use several methods to count the number of charged residues in the aggrecan core protein sequence; using find and replace in Word to count is perhaps the easiest way. This yields the following sequence data: Negatively charged residues: -1 x 106 D residues + -1 x 257 E residues = -363 Positively charged residues: +1 x 29 H residues + +1 x 25 K residues + +1 x 72 R residues = +126 Total charge: = -237 In Coulombs, total charge = -237 x x C = x C If histidine is assumed not to carry a charge, then the total charge drops to -266 x x C = x C It is also possible to count the numbers of each charged residue using a Matlab script; an example is given below. Since there is one aggrecan core protein in 25 nm x 25 nm area, the core protein areal surface charge = -237 x x C / (25 x 10-9 m) 2 = = C/m 2 (with charged histidines) or -266 x x C / (25 x 10-9 m) 2 = = C/m 2 (without charged histidines). Total surface charge per unit area is then the sum of the core protein and GAG contributions; the percentage of charge coming from the core protein is / ( ) * 100 = 2.33% (with charged histidines) or / ( ) * 100 = 2.59% (without charged histidines). Matlab script for charge count: function [n] = ChargeCount(seq) cols = length(seq); n = 0; for i = 1:cols, if strcmp(seq(i),'d') == 1 strcmp(seq(i),'e') == 1, n = n-1; elseif strcmp(seq(i), 'K') == 1 strcmp(seq(i),'r') == 1, n = n+1; elseif strcmp(seq(i), 'H') == 1, n = n+1; end end Matlab script for number of amino acids count: 10

11 function [n] = AACount(seq) cols = length(seq); n = zeros(6,1); for i = 1:cols, if strcmp(seq(i),'a') == 1, n(1) = n(1) + 1; elseif strcmp(seq(i),'d') == 1, n(2) = n(2) +1; elseif strcmp(seq(i),'e') == 1, n(3) = n(3) + 1; elseif strcmp(seq(i),'k') == 1, n(4) = n(4) + 1; elseif strcmp(seq(i),'r') == 1, n(5) = n(5) + 1; elseif strcmp(seq(i),'h') == 1, n(6) = n(6) + 1; end end e. Based on your answers to parts c. and d., can the linearized Poisson-Boltzmann Debye-Huckel formulation be employed to predict the EDL force? Why or why not? The linearized Poisson-Boltzman Debye-Huckel formulation is made with the assumption that surface potentials or charges are small; in lecture 16, slide 3, the guideline is given that surface potential should be less than 60 mv to use the linearized approximation. At an electrolyte concentration of 0.1M, a surface potential of 60 mv corresponds to a surface charge of σ = sinh(ψ 0 /53.4) c 0 = sinh(60/53.4) 0.1M = ~ C/m 2. At ~2.5 C/m 2, the surface charges per unit area on aggrecan are far above this guideline. The linearized approximation should not be used in this case. + 5 extra credit for posting a message on the podcast message board. 11

### Multimedia : Boundary Lubrication Podcast, Briscoe, et al. Nature , ( )

3.05 Nanomechanics of Materials and Biomaterials Thursday 04/05/07 Prof. C. Ortiz, MITDMSE I LECTURE 14: TE ELECTRICAL DOUBLE LAYER (EDL) Outline : REVIEW LECTURE #11 : INTRODUCTION TO TE ELECTRICAL DOUBLE

### 3.052 Nanomechanics of Materials and Biomaterials Tuesday 04/03/07 Prof. C. Ortiz, MIT-DMSE I LECTURE 13: MIDTERM #1 SOLUTIONS REVIEW

I LECTURE 13: MIDTERM #1 SOLUTIONS REVIEW Outline : HIGH RESOLUTION FORCE SPECTROSCOPY...2-10 General Experiment Description... 2 Verification of Surface Functionalization:Imaging of Planar Substrates...

### DLVO Theory and Non-DLVO Forces

NPTEL Chemical Engineering Interfacial Engineering Module 3: Lecture 5 DLVO Theory and Non-DLVO Forces Dr. Pallab Ghosh Associate Professor Department of Chemical Engineering IIT Guwahati, Guwahati 781039

### 3.052 Nanomechanics of Materials and Biomaterials Thursday 02/15/07 Prof. C. Ortiz, MIT-DMSE I LECTURE 4: FORCE-DISTANCE CURVES

I LECTURE 4: FORCE-DISTANCE CURVES Outline : LAST TIME : ADDITIONAL NANOMECHANICS INSTRUMENTATION COMPONENTS... 2 PIEZOS TUBES : X/Y SCANNING... 3 GENERAL COMPONENTS OF A NANOMECHANICAL DEVICE... 4 HIGH

### Basic Laboratory. Materials Science and Engineering. Atomic Force Microscopy (AFM)

Basic Laboratory Materials Science and Engineering Atomic Force Microscopy (AFM) M108 Stand: 20.10.2015 Aim: Presentation of an application of the AFM for studying surface morphology. Inhalt 1.Introduction...

### INTERMOLECULAR AND SURFACE FORCES

INTERMOLECULAR AND SURFACE FORCES SECOND EDITION JACOB N. ISRAELACHVILI Department of Chemical & Nuclear Engineering and Materials Department University of California, Santa Barbara California, USA ACADEMIC

### Interfacial forces and friction on the nanometer scale: A tutorial

Interfacial forces and friction on the nanometer scale: A tutorial M. Ruths Department of Chemistry University of Massachusetts Lowell Presented at the Nanotribology Tutorial/Panel Session, STLE/ASME International

### Lecture 6 Friction. Friction Phenomena Types of Friction

Lecture 6 Friction Tangential forces generated between contacting surfaces are called friction forces and occur to some degree in the interaction between all real surfaces. whenever a tendency exists for

### Single action pressing (from top)

www.komage.de Single action pressing (from top) Double action pressing with fixed die Typical course of the pressure during pressing and ejection (Single action) Upper punch Pressure Lower punch Time Green

### Molecular Forces in Biological Systems - Electrostatic Interactions; - Shielding of charged objects in solution

Molecular Forces in Biological Systems - Electrostatic Interactions; - Shielding of charged objects in solution Electrostatic self-energy, effects of size and dielectric constant q q r r ε ε 1 ε 2? δq

### Surface Tension: Liquids Stick Together Teacher Version

Surface Tension: Liquids Stick Together Teacher Version In this lab you will learn about properties of liquids, specifically cohesion, adhesion, and surface tension. These principles will be demonstrated

### Particle removal in linear shear flow: model prediction and experimental validation

Particle removal in linear shear flow: model prediction and experimental validation M.L. Zoeteweij, J.C.J. van der Donck and R. Versluis TNO Science and Industry, P.O. Box 155, 600 AD Delft, The Netherlands

### Lecture 3 Charged interfaces

Lecture 3 Charged interfaces rigin of Surface Charge Immersion of some materials in an electrolyte solution. Two mechanisms can operate. (1) Dissociation of surface sites. H H H H H M M M +H () Adsorption

### BIBC 100. Structural Biochemistry

BIBC 100 Structural Biochemistry http://classes.biology.ucsd.edu/bibc100.wi14 Papers- Dialogue with Scientists Questions: Why? How? What? So What? Dialogue Structure to explain function Knowledge Food

### Electrostatic Double Layer Force: Part III

NPTEL Chemical Engineering Interfacial Engineering Module 3: Lecture 4 Electrostatic Double Layer Force: Part III Dr. Pallab Ghosh Associate Professor Department of Chemical Engineering IIT Guwahati, Guwahati

### Physics and Chemistry of Interfaces

Hans Jürgen Butt, Karlheinz Graf, and Michael Kappl Physics and Chemistry of Interfaces Second, Revised and Enlarged Edition WILEY- VCH WILEY-VCH Verlag GmbH & Co. KGaA Contents Preface XI 1 Introduction

### Cohesion, Surface Tension, and Adhesion

Cohesion, Surface Tension, and Adhesion Content Objectives SWBAT describe how hydrogen bonding allows water molecules to maintain strong cohesion, adhesion, and surface tension. Van der Waals Forces The

### Friction: A Force That Opposes Motion

3 What You Will Learn The magnitude of the force of can vary. Kinetic is a force that, when unbalanced, can change the velocity of a moving object. Static balances an applied force and can prevent motion.

### 1. A tennis ball of mass m moving horizontally with speed u strikes a vertical tennis racket. The ball bounces back with a horizontal speed v.

1. A tennis ball of mass m moving horizontally with speed u strikes a vertical tennis racket. The ball bounces back with a horizontal speed v. The magnitude of the change in momentum of the ball is A.

### Lecture 2 and 3: Review of forces (ctd.) and elementary statistical mechanics. Contributions to protein stability

Lecture 2 and 3: Review of forces (ctd.) and elementary statistical mechanics. Contributions to protein stability Part I. Review of forces Covalent bonds Non-covalent Interactions: Van der Waals Interactions

### Module 8: "Stability of Colloids" Lecture 37: "" The Lecture Contains: DLVO Theory. Effect of Concentration. Objectives_template

The Lecture Contains: DLVO Theory Effect of Concentration file:///e /courses/colloid_interface_science/lecture37/37_1.htm[6/16/2012 1:02:12 PM] Studying the stability of colloids is an important topic

### MOLECULAR, CELLULAR, & TISSUE BIOMECHANICS

MOLECULAR, CELLULAR, & TISSUE BIOMECHANICS Spring 2015 Problem Set #6 - Cytoskeleton mechanics Distributed: Wednesday, April 15, 2015 Due: Thursday, April 23, 2015 Problem 1: Transmigration A critical

### The four forces of nature. Intermolecular forces, surface forces & the Atomic Force Microscope (AFM) Force- and potential curves

Intermolecular forces, surface forces & the Atomic Force Microscope (AFM) The four forces of nature Strong interaction Holds neutrons and protons together in atomic nuclei. Weak interaction β and elementary

### Station 1 Water is a polar molecule and has a very unique structure

Station 1 Water is a polar molecule and has a very unique structure A water molecule, because of its shape, is a polar molecule. That is, it has one side that is positively charged and one side that is

### SCALING OF THE ADHESION BETWEEN PARTICLES AND SURFACES FROM MICRON-SCALE TO THE NANOMETER SCALE FOR PHOTOMASK CLEANING APPLICATIONS

SCALING OF THE ADHESION BETWEEN PARTICLES AND SURFACES FROM MICRON-SCALE TO THE NANOMETER SCALE FOR PHOTOMASK CLEANING APPLICATIONS Gautam Kumar, Shanna Smith, Florence Eschbach, Arun Ramamoorthy, Michael

### ME 230 Kinematics and Dynamics

ME 230 Kinematics and Dynamics Wei-Chih Wang Department of Mechanical Engineering University of Washington Lecture 8 Kinetics of a particle: Work and Energy (Chapter 14) - 14.1-14.3 W. Wang 2 Kinetics

### LECTURE 9 FRICTION & SPRINGS. Instructor: Kazumi Tolich

LECTURE 9 FRICTION & SPRINGS Instructor: Kazumi Tolich Lecture 9 2 Reading chapter 6-1 to 6-2 Friction n Static friction n Kinetic friction Springs Static friction 3 Static friction is the frictional force

### Phys101 Lectures 9 and 10 Conservation of Mechanical Energy

Phys101 Lectures 9 and 10 Conservation of Mechanical Energy Key points: Conservative and Nonconservative Forces Potential Energy Generalized work-energy principle Mechanical Energy and Its Conservation

### File ISM04. Properties of Colloids I

File ISM04 Properties of Colloids I 1 Colloids Small things, but much bigger than a molecule Background: Foundations of Colloid Science Vol I & II, R.J. Hunter Physical Chemistry, P.W. Atkins, Chapter

### István Bányai, University of Debrecen Dept of Colloid and Environmental Chemistry

Colloid stability István Bányai, University of Debrecen Dept of Colloid and Environmental Chemistry www.kolloid.unideb.hu (Stability of lyophilic colloids see: macromolecular solutions) Stabilities 1.

### A General Equation for Fitting Contact Area and Friction vs Load Measurements

Journal of Colloid and Interface Science 211, 395 400 (1999) Article ID jcis.1998.6027, available online at http://www.idealibrary.com on A General Equation for Fitting Contact Area and Friction vs Load

### To investigate three types of friction and to measure the coefficient of friction for each type

Name Period Date Chapter 6: Newton's Second Law of Motion Force and Acceleration Coefficients of Friction 33 Slip-Stick Purpose To investigate three types of friction and to measure the coefficient of

### Atoms, electrons and Solids

Atoms, electrons and Solids Shell model of an atom negative electron orbiting a positive nucleus QM tells that to minimize total energy the electrons fill up shells. Each orbit in a shell has a specific

### Atomic Force Microscopy imaging and beyond

Atomic Force Microscopy imaging and beyond Arif Mumtaz Magnetism and Magnetic Materials Group Department of Physics, QAU Coworkers: Prof. Dr. S.K.Hasanain M. Tariq Khan Alam Imaging and beyond Scanning

### Physics-MC Page 1 of 29 Inertia, Force and Motion 1.

Physics-MC 2006-7 Page 1 of 29 Inertia, Force and Motion 1. 3. 2. Three blocks of equal mass are placed on a smooth horizontal surface as shown in the figure above. A constant force F is applied to block

### SAM Teachers Guide Intermolecular Forces Overview Learning Objectives: Possible student pre/misconceptions

SAM Teachers Guide Intermolecular Forces Overview This unit focuses on the attractive forces felt between molecules. Both London Dispersion and Dipole Dipole intermolecular attractions will be discussed

### Conception mécanique et usinage MECA Hydrodynamic plain bearings

Conception mécanique et usinage MECA0444-1 Hydrodynamic plain bearings Pr. Jean-Luc BOZET Dr. Christophe SERVAIS Année académique 2016-2017 1 Tribology Tribology comes from the greek word tribein, which

### HYDROPHOBIC FORCES IN FLOTATION. Rajesh Pazhianur ABSTRACT

HYDROPHOBIC FORCES IN FLOTATION Rajesh Pazhianur ABSTRACT An atomic force microscope (AFM) has been used to conduct force measurements to better understand the role of hydrophobic forces in flotation.

### PHYSICS 218 EXAM 2 Tuesday, October 26, 2010

PHYSICS 218 EXAM 2 Tuesday, October 26, 2010 NAME: SECTION: 513 514 515 516 Note: 513 Recitation & lab Wed 8:00-10:50 am 514 Recitation & lab Wed 11:30 am - 2:20 pm 515 Recitation & lab Wed 3:00-5:50 pm

### V. Electrostatics Lecture 24: Diffuse Charge in Electrolytes

V. Electrostatics Lecture 24: Diffuse Charge in Electrolytes MIT Student 1. Poisson-Nernst-Planck Equations The Nernst-Planck Equation is a conservation of mass equation that describes the influence of

### Influence of Enterococcal Surface Protein (esp) on the Transport of Enterococcus faecium within Saturated Quartz Sands

Influence of Enterococcal Surface Protein (esp) on the Transport of Enterococcus faecium within Saturated Quartz Sands Jennifer J. Johanson, Lucia Feriancikova, Shangping Xu* Department of Geosciences

### Chemistry in Biology Section 1 Atoms, Elements, and Compounds

Name Chemistry in Biology Section 1 Atoms, Elements, and Compounds Date Main Idea Details Scan the headings and boldfaced words in Section 1 of the chapter. Predict two things that you think might be discussed.

### Chapter 11. Liquids and Intermolecular Forces

Chapter 11. Liquids and Intermolecular Forces 11.1 A Molecular Comparison of Gases, Liquids, and Solids Gases are highly compressible and assume the shape and volume of their container. Gas molecules are

### AP Biology Summer Assignment

AP Biology Summer Assignment Welcome to AP Biology! The two main goals of AP Biology are to help you develop a conceptual framework for modern biology and to gain a deeper appreciation of science as a

### Unit 6 Forces and Pressure

Unit 6 Forces and Pressure Lesson Objectives: Mass and weight Gravitational field and field strength describe the effect of balanced and unbalanced forces on a body describe the ways in which a force may

### 2-1 The Nature of Matter. Atoms

2-1 The Nature of Matter Atoms What do we call the smallest unit of matter? Who named it? What does it mean in Greek? How many atoms would make a row 1cm long? What does this indicate? Atoms are made up

### Forces. Unit 2. Why are forces important? In this Unit, you will learn: Key words. Previously PHYSICS 219

Previously Remember From Page 218 Forces are pushes and pulls that can move or squash objects. An object s speed is the distance it travels every second; if its speed increases, it is accelerating. Unit

### STATICS. Friction VECTOR MECHANICS FOR ENGINEERS: Eighth Edition CHAPTER. Ferdinand P. Beer E. Russell Johnston, Jr.

Eighth E 8 Friction CHAPTER VECTOR MECHANICS FOR ENGINEERS: STATICS Ferdinand P. Beer E. Russell Johnston, Jr. Lecture Notes: J. Walt Oler Texas Tech University Contents Introduction Laws of Dry Friction.

### 7.012 Problem Set 1 Solutions

ame TA Section 7.012 Problem Set 1 Solutions Your answers to this problem set must be inserted into the large wooden box on wheels outside 68120 by 4:30 PM, Thursday, September 15. Problem sets will not

### Lecture 11: Protein Folding & Stability

Structure - Function Protein Folding: What we know Lecture 11: Protein Folding & Stability 1). Amino acid sequence dictates structure. 2). The native structure represents the lowest energy state for a

### 27 Gecko Feet: Natural Attachment Systems for Smart Adhesion Mechanism, Modeling, and Development of Bio-Inspired Materials

27 Gecko Feet: Natural Attachment Systems for Smart Adhesion Mechanism, Modeling, and Development of Bio-Inspired Materials Bharat Bhushan Robert A. Sayer Abstract. Several creatures, including insects,

### Extra credit assignment #4 It can be handed in up until one class before Test 4 (check your course outline). It will NOT be accepted after that.

Extra credit assignment #4 It can be handed in up until one class before Test 4 (check your course outline). It will NOT be accepted after that. NAME: 4. Units of power include which of the following?

### PHY 481/581. Some classical/quantum physics for the nanometer length scale.

PHY 481/581 Some classical/quantum physics for the nanometer length scale http://creativecommons.org/licenses/by-nc-sa/3.0/ 1 What is nano-science? the science of materials whose properties scale with

### (1) (3)

1. This question is about momentum, energy and power. (a) In his Principia Mathematica Newton expressed his third law of motion as to every action there is always opposed an equal reaction. State what

### They are similar to each other

They are similar to each other Different than gases. They are incompressible. Their density doesn t change much with temperature. These similarities are due to the molecules staying close together in solids

There are two types of polysaccharides in cell: glycogen and starch Starch and glycogen are polysaccharides that function to store energy Glycogen Glucose obtained from primary sources either remains soluble

### They are similar to each other. Intermolecular forces

s and solids They are similar to each other Different than gases. They are incompressible. Their density doesn t change much with temperature. These similarities are due to the molecules staying close

### Engineering Mechanics. Friction in Action

Engineering Mechanics Friction in Action What is friction? Friction is a retarding force that opposes motion. Friction types: Static friction Kinetic friction Fluid friction Sources of dry friction Dry

### Fluid flow Pressure Bernoulli Principle Surface Tension

Lecture 9. Fluid flow Pressure Bernoulli Principle Surface Tension A v L A is the area Fluid flow Speed of a fluid in a pipe is not the same as the flow rate Relating: Fluid flow rate to Average speed

### Unit 2: Chemistry. Unit Overview:

Unit 2: Chemistry Unit Overview: This unit will focus on basic chemistry and some of the major process of organic chemistry (dehydration synthesis, hydrolysis, and enzyme action) that help form carbon

### Colloidal Crystal: emergence of long range order from colloidal fluid

Colloidal Crystal: emergence of long range order from colloidal fluid Lanfang Li December 19, 2008 Abstract Although emergence, or spontaneous symmetry breaking, has been a topic of discussion in physics

### 2. As gas P increases and/or T is lowered, intermolecular forces become significant, and deviations from ideal gas laws occur (van der Waal equation).

A. Introduction. (Section 11.1) CHAPTER 11: STATES OF MATTER, LIQUIDS AND SOLIDS 1. Gases are easily treated mathematically because molecules behave independently. 2. As gas P increases and/or T is lowered,

### 3rd Grade. Forces and Motion Review. Slide 1 / 106 Slide 2 / 106. Slide 4 / 106. Slide 3 / 106. Slide 5 / 106. Slide 6 / 106. Motion and Stability

Slide 1 / 106 Slide 2 / 106 3rd Grade Motion and Stability 2015-11-09 www.njctl.org Slide 3 / 106 Slide 4 / 106 Table of Contents Forces and Motion Review Balanced and Unbalanced Forces Motion prediction

### Stability of colloidal systems

Stability of colloidal systems Colloidal stability DLVO theory Electric double layer in colloidal systems Processes to induce charges at surfaces Key parameters for electric forces (ζ-potential, Debye

### Protein structure (and biomolecular structure more generally) CS/CME/BioE/Biophys/BMI 279 Sept. 28 and Oct. 3, 2017 Ron Dror

Protein structure (and biomolecular structure more generally) CS/CME/BioE/Biophys/BMI 279 Sept. 28 and Oct. 3, 2017 Ron Dror Please interrupt if you have questions, and especially if you re confused! Assignment

### Lecture Notes 1: Physical Equilibria Vapor Pressure

Lecture Notes 1: Physical Equilibria Vapor Pressure Our first exploration of equilibria will examine physical equilibria (no chemical changes) in which the only changes occurring are matter changes phases.

### Chapter 10: States of Matter. Concept Base: Chapter 1: Properties of Matter Chapter 2: Density Chapter 6: Covalent and Ionic Bonding

Chapter 10: States of Matter Concept Base: Chapter 1: Properties of Matter Chapter 2: Density Chapter 6: Covalent and Ionic Bonding Pressure standard pressure the pressure exerted at sea level in dry air

### SCHOOL OF COMPUTING, ENGINEERING AND MATHEMATICS SEMESTER 1 EXAMINATIONS 2012/2013 XE121. ENGINEERING CONCEPTS (Test)

s SCHOOL OF COMPUTING, ENGINEERING AND MATHEMATICS SEMESTER EXAMINATIONS 202/203 XE2 ENGINEERING CONCEPTS (Test) Time allowed: TWO hours Answer: Attempt FOUR questions only, a maximum of TWO questions

### Nano-Attach Project. Hope Chik, Motorola Celestica-iNEMI Technology Forum May 15, 2007

Nano-Attach Project Hope Chik, Motorola Celestica-iNEMI Technology Forum May 15, 2007 Outline Motivation Nanotechnology Advantages Approaches Biomimetic Nano-Velcro inemi Nano-Attach Project 1 Motivation

### Colloid stability. Lyophobic sols. Stabilization of colloids.

Colloid stability. Lyophobic sols. Stabilization of colloids. Lyophilic and lyophobic sols Sols (lyosols) are dispersed colloidal size particles in a liquid medium (=solid/liquid dispersions) These sols

### UNIVERSITY OF SASKATCHEWAN Department of Physics and Engineering Physics

UNIVERSITY OF SASKATCHEWAN Department of Physics and Engineering Physics Physics 115.3 Physics and the Universe FINAL EXAMINATION December 14, 013 NAME: (Last) Please Print (Given) Time: 3 hours STUDENT

### SAM Teachers Guide Chemical Bonds

SAM Teachers Guide Chemical Bonds Overview Students discover that the type of bond formed ionic, non polar covalent, or polar covalent depends on the electronegativity of the two atoms that are bonded

### I pt mass = mr 2 I sphere = (2/5) mr 2 I hoop = mr 2 I disk = (1/2) mr 2 I rod (center) = (1/12) ml 2 I rod (end) = (1/3) ml 2

Fall 008 RED Barcode Here Physics 105, sections 1 and Exam 3 Please write your CID Colton -3669 3 hour time limit. One 3 5 handwritten note card permitted (both sides). Calculators permitted. No books.

### SIMULATION IN MAGNETIC FIELD ENHANCED CENTRIFUGATION

SIMULATION IN MAGNETIC FIELD ENHANCED CENTRIFUGATION Dipl.-Ing. Johannes Lindner*, Dipl.-Ing. Katharina Menzel, Prof. Dr.-Ing. Hermann Nirschl Institute of Mechanical Process Engineering and Mechanics

### What Causes Friction?

What Causes Friction? Friction is the force that opposes the motion between two surfaces that touch (parallel to the surface). The surface of any object is rough. Even an object that feels smooth is covered

### PHY218 SPRING 2016 Review for Final Exam: Week 14 Final Review: Chapters 1-11, 13-14

Final Review: Chapters 1-11, 13-14 These are selected problems that you are to solve independently or in a team of 2-3 in order to better prepare for your Final Exam 1 Problem 1: Chasing a motorist This

### Supplementary Figure 1 Experimental setup for crystal growth. Schematic drawing of the experimental setup for C 8 -BTBT crystal growth.

Supplementary Figure 1 Experimental setup for crystal growth. Schematic drawing of the experimental setup for C 8 -BTBT crystal growth. Supplementary Figure 2 AFM study of the C 8 -BTBT crystal growth

### Chapter 6 Stability of Colloidal Suspensions

Chapter 6 Stability of Colloidal Suspensions 6.1 Kinetic Stability of Colloidal Suspensions o G = A f sl sl interfacial surface tension (sol/liq) [J/m 2 ] sol/liq surface change [m 2 ] γ sl > 0 colloid

### Atomic and Molecular Dimensions

1 Atomic and Molecular Dimensions Equilibrium Interatomic Distances When two atoms approach each other, their positively charged nuclei and negatively charged electronic clouds interact. The total interaction

### Announcements. Principle of Work and Energy - Sections Engr222 Spring 2004 Chapter Test Wednesday

Announcements Test Wednesday Closed book 3 page sheet sheet (on web) Calculator Chap 12.6-10, 13.1-6 Principle of Work and Energy - Sections 14.1-3 Today s Objectives: Students will be able to: a) Calculate

### FRICTION. Friction: FRICARE = to rub (Latin)

FRICTION 1 Friction: FRICARE = to rub (Latin) Resisting force (F) tangential to the interface between two bodies when, under the action of an external force, one body moves or tends to move relative to

### The peeling behavior of thin films with finite bending sti ness and the implications on gecko adhesion

The peeling behavior of thin films with finite bending sti ness and the implications on gecko adhesion Roger A. Sauer 1 Aachen Institute for Advanced Study in Computational Engineering Science (AICES),

### Adhesion and Detachment Characteristics of Soft. adhesive tapes to gecko hairy foot pads. Boxin Zhao, Ph.D.

Adhesion and Detachment Characteristics of Soft Adhesive Systems: from pressure-sensitivesensitive adhesive tapes to gecko hairy foot pads Boxin Zhao, Ph.D. Assistant Professor Waterloo Institute for Nanotechnology,

### PHYSICS 149: Lecture 21

PHYSICS 149: Lecture 21 Chapter 8: Torque and Angular Momentum 8.2 Torque 8.4 Equilibrium Revisited 8.8 Angular Momentum Lecture 21 Purdue University, Physics 149 1 Midterm Exam 2 Wednesday, April 6, 6:30

### Liquids and Intermolecular Forces. Course Learning Outcomes for Unit I. Reading Assignment. Unit Lesson UNIT I STUDY GUIDE

UNIT I STUDY GUIDE Liquids and Intermolecular Forces Course Learning Outcomes for Unit I Upon completion of this unit, students should be able to: 1. Identify the intermolecular attractive interactions

### Physics 221. Exam III Spring f S While the cylinder is rolling up, the frictional force is and the cylinder is rotating

Physics 1. Exam III Spring 003 The situation below refers to the next three questions: A solid cylinder of radius R and mass M with initial velocity v 0 rolls without slipping up the inclined plane. N

### Consider the case of a 100 N. mass on a horizontal surface as shown below:

1.9.1 Introduction The study of friction is called: The force of friction is defined as: The force of friction acting between two surfaces has three properties: i) ii) iii) Consider the case of a 100 N.

### Physics 218 Exam II. Fall 2017 (all sections) October 25 th, 2017

Physics 218 Exam II Fall 2017 (all sections) October 25 th, 2017 Please fill out the information and read the instructions below, but do not open the exam until told to do so. Rules of the exam: 1. You

### b) Fluid friction: occurs when adjacent layers in a fluid are moving at different velocities.

Ch.6 Friction Types of friction a) Dry friction: occurs when non smooth (non ideal) surfaces of two solids are in contact under a condition of sliding or a tendency to slide. (also called Coulomb friction)

### Theme 2 - PHYSICS UNIT 2 Forces and Moments. A force is a push or a pull. This means that whenever we push or pull something, we are doing a force.

Forces A force is a push or a pull. This means that whenever we push or pull something, we are doing a force. Forces are measured in Newtons (N) after the great physicist Sir Isaac Newton. The instrument

### Lecture Presentation. Chapter 11. Liquids and Intermolecular Forces Pearson Education, Inc.

Lecture Presentation Chapter 11 Liquids and States of Matter The fundamental difference between states of matter is the strength of the intermolecular forces of attraction. Stronger forces bring molecules

### Summer Physics 41 Pretest. Shorty Shorts (2 pts ea): Circle the best answer. Show work if a calculation is required.

Summer Physics 41 Pretest Name: Shorty Shorts (2 pts ea): Circle the best answer. Show work if a calculation is required. 1. An object hangs in equilibrium suspended by two identical ropes. Which rope

### AP Physics. Chapters 7 & 8 Review

AP Physics Chapters 7 & 8 Review 1.A particle moves along the x axis and is acted upon by a single conservative force given by F x = ( 20 4.0x)N where x is in meters. The potential energy associated with

### Non-equilibrium molecular dynamics simulations of organic friction modifiers

Non-equilibrium molecular dynamics simulations of organic friction modifiers James Ewen PhD Student Tribology Group (Shell UTC) Imperial College London Session 8B Bronze 2 Lubrication Fundamentals STLE

### Ionic Strength and Composition affect the mobility of surface-modified

Ionic Strength and Composition affect the mobility of surface-modified Fe 0 Nanoparticles in water-saturated sand columns. Navid Saleh 1, Hye-Jin Kim 1, Tanapon Phenrat 1, Krzysztof Matyjaszewski 3, Robert

### Structural and Mechanical Properties of Nanostructures

Master s in nanoscience Nanostructural properties Mechanical properties Structural and Mechanical Properties of Nanostructures Prof. Angel Rubio Dr. Letizia Chiodo Dpto. Fisica de Materiales, Facultad

### The Chemical Context of Life

Chapter 2 The Chemical Context of Life PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from

### Module 14 Brief overview of bearings. Version 2 ME, IIT Kharagpur

Module 14 Brief overview of bearings Lesson 1 Fluid Film bearings Instructional Objectives: At the end of this lesson, the students should be able to understand: Types of bearings Comparison of bearing