University of Wisconsin MRSEC Macro Micro Nano

University of Wisconsin MRSEC Can see with your eyes Micro Red blood cells Nano DNA (width) Macro Grains of sand Often requires a microscope to see Requires a highly specialized microscope, such as a Scanning Electron Microscope (SEM), to see

University of Wisconsin MRSEC Contact Angle High contact angle Low contact angle Hydrophobic surface Hydrophilic surface

University of Wisconsin MRSEC Making Predictions 1. Examine the slide under the microscope 2. Predict how a drop of water will behave RoundedFlat OR

University of Wisconsin MRSEC SEM of Soot Int. J. Electrochem. Sci., 6 (2011) 1269 – 1276

University of Wisconsin MRSEC What is nanotechnology? 1.The nanometer is extremely small. 2.At the nanometer scale, many things behave differently. 3.We can use this new behavior to make new technologies.

University of Wisconsin MRSEC What is nanotechnology? Nanotechnology is the understanding and control of matter 1 to 100 nanometers in size.

University of Wisconsin MRSEC Nanotechnology Scientists coat surfaces with nanoparticles to prevent biofouling, seen here on a submarine. Anti-biofouling applications

University of Wisconsin MRSEC Nanotechnology Biomedical applications Research is currently underway that incorporates nano-sized features on implants to prevent bacterial growth, and to encourage the body grow the correct type of cells on the implant.

University of Wisconsin MRSEC The Lotus Effect Lotus leaves and nasturtium leaves are self-cleaning due to nano and microscale structures and a waxy coating. Together these features create a superhydrophobic surface. Close-up of a nasturtium leaf, which exhibits the Lotus Effect, with a droplet of water

University of Wisconsin MRSEC The Lotus Effect

University of Wisconsin MRSEC Hydrophobic Surfaces Water “fearing” Repel water Non-polar Rounded water drop

University of Wisconsin MRSEC Superhydrophobic Surfaces VERY water “fearing” Non-polar Nano-scale surface features Water rolls off when surface is held at an angle Water drop is very rounded (contact angle greater than 150 ° )

University of Wisconsin MRSEC Hydrophilic Surfaces Water “loving” Polar Flat water drop Water drop may absorb into material Leaves a streak of water when rolling off

University of Wisconsin MRSEC Chemical Formula: H 2 O 2 Hydrogens covalently bonded to 1 Oxygen Water Covers 70% of the Earth’s surface! Essential for life Universal solvent The only molecule that exists naturally as a gas, liquid, and solid Unique properties Water Molecule

University of Wisconsin MRSEC Properties of Water 1.Polarity 2.Hydrogen Bonding 3.High Surface Tension

University of Wisconsin MRSEC δ+ Polarity of Water Water is polar! Oxygen attracts electrons much more strongly than hydrogen Partially negative Partially positive δ-

University of Wisconsin MRSEC Hydrogen Bonding Attraction between water molecules

University of Wisconsin MRSEC Surface Tension of Water Polarity and Hydrogen Bonding cause water to form a “skin” of molecules at the surface