Are you tense?

1. Texas A&M E3 Research Program Microfluidics in the Classroom Summer 2007 Saleen Mitchell & Amanda Kennedy Are you tense? Well, RELAX

2. Microfluidics in the classroomSaleen Mitchell & Amanda Kennedy Day 1: Intro. to Engineering and its importance in every day life. Day 2: Introduce basic principle of hydrophobic and hydrophilic (Qualitative Lab) Day 3: Introduce surface tension, surfactants and show how it correlates with hydrophobic, hydrophilic and amphiphilic properties. (Qualitative Lab) Day 4 & 5: Formation of Water Droplets and use of “student- friendly” microfluidics device.

3. Objectives: The learner will investigate and analyze… • Surface Tension in our daily lives • Surface Tension as it relates to different substances • Surface Tension as it relates to surfactants • Surface Tension and Microfluidics

4. Lets InvestigateSurface Tension: Have you ever wondered how your dirty, dingy socks become clean in the washer? How do the small granules of detergent “clean”? Why are they effective? How come bugs can walk on water but we cant? • Prior knowledge • Polar nature of water • Basic atomic structure • Characteristics of matter • Hydrophillic vs. Hydrophobic

5. Surface tensionresults from the fact that the water molecules prefers to stick to itself (the other water molecules) than to the air above it. So a kind of "skin" forms on the water surface where the water molecules are holding onto each other tightly and not interacting with the air above it very much. It plays a role in washing and cleaning procedures as well as in lubricants as used in automobiles and cosmetics. THE BASICS:Surface Tension Defined

6. Surface Tension & Surfactants OBJECTIVE: To investigate how surfactants decrease surface tension in various applications. Activities: “Leafy Clean” “Scared Pepper” “Balloon on a Spool” Major Project Build your own Microfluidic Device Respiratory Disease Brochure Insect Locomotion Research Click to link

7. Surface Active Agents Molecules that break surface tension have polar (water-loving/oil-hating) and non-polar (water-hating/oil- loving) parts. • Surfactants are chemicals that alter the surface tension between different substances, allowing easier spreading, and lower the interfacial tension between two liquids. • Surfactants reduce the surface tension of water by adsorbing at the liquid-gas interface. • Soaps or detergents are surfactants. You use shampoo or soap to clean yourself, because oils and other dirt dissolves better in water when they are present.

8. Scared Pepper Leafy clean Some materials are hydrophilic meaning that they like water, others are hydrophobic meaning that they hate water. It has to do with the chemistry of the surface. Wax is made up of chemicals that don’t like water. Sometimes you can make a material hydrophobic or hydrophilic by just treating it in a special way. Plastics can be treated with different things to give you materials that repel water or attract water. Lotus leaves have tiny hairs that are only a few hundred nanometers in size. These hairs are hydrophobic and help to bead up water, and when the bead gets big enough it forms a drop and rolls down the leaf. Surface tension creates the "skin" on top of the water, the surface tension of the pepper particles is less than "pure" water so the pepper particles tend to float on the water's surface. When you add a drop of soap, you greatly reduce the surface tension of the water near the point at which you add the soap. Initially, this causes a repulsion of the pepper particles and the particles tend to follow the high surface tension areas. .

9. Let’s InvestigateSurface Tension & Breathing: Do we only sigh when we’re bored, or is there a deeper purpose? • Prior knowledge • Lung Compliance • Gas Laws • Respiratory System Anatomy

10. “BALLOONS ON A SPOOL” PURPOSE: • The purpose of this activity is to determine how the size of a balloon affects the air pressure and the surface tension or contracting pull in the balloon. • MATERIALS: (Refer to procedure sheet) • PROCEDURE: (Refer to procedure sheet) • Remove the twist-tie from the larger balloon.  What do you observe? • Predict what will happen to the size of the two balloons if the twist-tie is removed from the larger balloon. EXTENDED APPLICATION: To describe how the compliance and resistance of the respiratory system influence breathing under normal conditions and how they may be alteredby disease. --Respiratory Disease Brochure

11. What happened? LaPlace’s Law tells us that the pressure within a spherical structure with surface tension, such as the alveolus, is inversely proportional to the radius of the sphere P=2T/r (for a sphere with one liquid-gas interface, like an alveolus) P=pressure, T=surface tension r=radius The small balloon blew up the larger one, and got smaller WHY? It’s due to surface tension effects. • The rubber is thicker in a smaller balloon, and thus produces greater surface tension. The surface tension or stretch of the balloon is greater when it is small than when it is large.  That larger surface tension causes the smaller balloon to force its air into the larger balloon.

12. T P1 r1 T P2 Result: Total Collapses r2 LaPlace’s Law • That is, at a constant surface tension, small alveoli will generate bigger pressures within them than will large alveoli. Smaller alveoli would therefore be expected to empty into larger alveoli as lung volume decreases. • At every gas-liquid interface surface tension develops. • Surface Tension is a liquid property

13. So, do our lungs act like these balloons? The difference between the alveoli and the balloons is that there are TWO additional forces that have impacts on the distribution of gas within them. • One is the fact that the alveoli (lungs) DO NOT deflate completely during exhalation. • The other is that the surface tension of the alveoli can be altered by the processes that occur within them. Without the alterations of surface tension in the alveoli, all air inhaled would go to the larger alveoli. This would be very inefficient because blood is flowing past all the alveoli and only some would have fresh gas in them to allow oxygen to diffuse into the blood flowing past them.

14. THE BASICS:Surfactant in the Lungs One of the remarkable phenomena in the process of respirationis the role of the fluid coating the walls of thealveoli of the lungs. This fluid, called a surfactant, lowers the surface tension of the balloon-like alveoli by about a factor of 15 compared to the normal mucous tissue fluid in which they are immersed

15. GREAT PLEASE TAKE A DEEP BREATH! • To have enough surfactant in the alveoli, two things are needed. • the cells must be able to synthesize surfactant. • the alveolar wall must be stretched significantly every few minutes to keep will sigh every few minutes surfactant being secreted. Normally people will sigh every few minutes to keep the alveoli inflated. Pain, lack of mobility, bed-rest, lack of muscle strength and diminished level of consciousness can all interfere with a person taking the deep breaths. Lack of deep breaths will result in decreased secretion of surfactant into alveoli in some areas. Decreased level of surfactant leads to collapse of the alveoli (atelectasis). When alveoli collapse, there is less surface area for diffusion of oxygen into the bloodstream.

16. “Relate this TO ME ”  . Remember, aveoli are like “small balloons” & everyone knows that it is much more difficult to blow up a balloon for the first time. The alveoliof the lungs are collapsed in the fetus and must be inflated in the process of inhalation, so the purpose of the traditional spank on the bottom of the newborn is to make him/her mad enough to make the effort for the first breath and stimulate the surfactant fluid in the alveoli.

17. Physiological Importance of Surfactant • They prevent water droplets from blocking airways .Promotes dry alveoli • Increases lung compliance (less stiff) • Promotes alveolar stabilityand prevents alveolar collapse, because surfactant differentially reduces surface tension. *Decreased surface area lowers surface tension. *Increased surface area increases surface tension. *Small alveoli are prevented from getting smaller. *Large alveoli are prevented from getting bigger

18. Microfluidics:Developing micro-reactors Can a perfect droplet be fabricated that will encapsulate a living cell? • Prior knowledge • The surface tension of water provides the necessary wall tension for the formation of bubbles with water. • The tendency to minimize that wall tension pulls the bubbles into spherical shapes (LaPlace Law)

19. THE BASICS:Surface Tension and Droplets Surface Tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. The spherical shape minimizes then necessary "wall tension" of the surface layer according to LaPlace's law.

20. THE BASICS:Surface Tension and Microfluidics Microfluidics is the science of manipulating micro-liter and nano-liter volumes of fluids or gases in a miniaturized system of channels, pumps or valves. • It studies how these behaviors can change, how they can be worked around, or exploited for new uses.

21. Advantages • Immunoisolation • Natural therautic response • Applications • Diabetes (type I) • Hemophilia • Cancer • Renal failure Cell Encapsulation: concept • Encapsulate cells of interest in semi-permeable membrane • Implant cell capsules • Cells release therapeutic substances

22. Find the Engineer inside: Build your own Microfluidic Device! • PURPOSE:Hands-on method for students to make droplets and participate in the simulation of cell encapsulation • MATERIALS:(Refer to procedure sheet) • PROCEDURE:(Refer to procedure sheet)

23. Materials Needed Making the Device

24. Materials Needed

25. Student Use Click here for procedure Valve used for the transfer of fluid to the dropper for creation of drop. Potentiometer used to vary the speed of rotation of fluid. Pressure from duster used to push fluid into the petri dish. Syringe used to input fluid into valve before it can be placed in the petri dish. Fan used to rotate material thereby resulting in liquid moving to the sides of the container due to centripetal force

26. Microfluidics in Action

27. What happened? • What effect does varying the speed have on the size of the droplets? • What effect does varying the amount of surfactant used have on the results? • How do the size of the droplets relate to the surface tension of the device • Were the droplets uniform? What adaptations would you make to the design of the device to produce uniform drops? • Were you able to encapsulate the biological- yeast or Escherichia coli ? Why or Why not. • What are your constraints you encounter when using biological agents?

28. POTENTIAL APPLICATIONS Microfluidic systems have great potential to perform complex chemical and biological processing and analysis on a single disposable chip. • process analysis • environmental monitoring • clinical diagnostics: hemophilia • drug discovery: diabetes, cancer • culturing and manipulating cells • protein analysis • DNA sizing and sequencing • all-optical particle sorter Nature Materials3, 9 - 10 (2004) doi:10.1038/nmat1041

29. THANK YOU PENG… Grown and Sexy Don’t get cut! I’m glad they’re GONE!

30. …and especially to Dr. Cheng There he is!