hoowaki overview linked inv2

OverviewFall 2009

transforming surfaces

2 August 2009transforming surfaces

Contents1. Introduction

2. Surface modification technology overview

3. Hoowaki’s micro-molding technology

4. Applications

5. Working with Hoowaki

6. Contact Information

4. Applications

Hoowaki LLC

Hoowaki is based in South Carolina at the Clemson Center for Applied Technology and is commercializing technology developed at the University of Illinois at Urbana-Champaign,

Hoowaki Engineers Surfaces

Conventional non-engineered surfaceRandom distribution of sizes and shapes

Highly-engineered surfaceDesigned distribution of sizes and shapes

Hoowaki LLC

Colored water droplets on the surface of molded Santoprene rubber.

Surface micro-structures clearly visible through the droplets (structures are in the 50 micron range)

Hoowaki - Key staff

• Ralph Hulseman, President - 25 years with Michelin R&D. Experience in target markets

• William King PhD, CTO - Professor of Mechanical Engineering at the University of Illinois Urbana-Champaign. Technology Inventor

• John Warner, CFO - Entrepreneur and Chairman of “InnoVenture”

• Scott Denley, VP Manufacturing and Quality – 28 years with Michelin

• March Maguire, VP Engineering – 20 years with Kemet

• Doug Wilson PhD, VP Business Development -25 years in advanced materials new business development.

• Bob Mammarella PhD, Chief Scientist – 30 years with Fuji and Polaroid in product development R&D and process engineering

4. Applications

Surface Modification• Surface properties

differ from those of bulk materials

• Such properties can strongly influence the functions that contribute to product value

• Many of these properties occur at the meso level

Bulk vs. Meso vs. Chemical Scale

Bulk Scale: Man-made,

movable objects

Meso Scale, 0.1mm to 10

nm: Unseen by the

naked eye - properties

independent of bulk material

Molecular Scale:

Chemical interactions - affects meso

Bulk vs. Meso vs. Chemical Scale

Meso: design nanometer to micrometer sized features

Engineering attributes at each of the three size scales can optimize the performance of a

man-made object

There is an equal range of design potential at the meso

scale as at the bulk scale

Properties of Well-Studied Scales

Scale Properties

Bulk Stiffness, density, diffusivity, solubility, yield strength, electrical conductivity, magnetic properties, capacitance, sound conductivity, hysteric vibration damping and thermal conductivity

Properties of Well-Studied Scales

Scale Properties

Molecular Chemical reactivity, catalysis, molecular mobility and inter-diffusion, light adsorption, van de Waals forces, hydrogen bonding and chemical bond strength

Manufacturing the Meso scale

• Until recently, the meso scale was difficult to engineer

• Existing manufacturing processes generally created size distributions of randomly shaped and sized objects• Examples: Sanding, grinding, etching, bead blasting and polishing

• Emerging manufacturing processes: micromachining, laser machining, lithography, micro-molding

It is now possible to engineer performance attributes contributed to by the meso scale

Meso-scale Structures Dramatically Influence the

Properties of a SurfacePerformance

attributeDescription

Appearance Reflection of light: shiny, matte, shades of color, iridescence, photonic light manipulation

Touch Interaction with nerve endings: density of points of contact, their shape, stiffness, flexibility, perhaps electrical behavior

Surface tension Interactions of fluids with solids: hydrophobic and hydrophilic behavior. Changing roughness at the meso scale is necessary to create super-hydrophobic behavior.

Nucleation Crystallization, boiling, and cavitation are examples

Bloom Balance of bulk chemical concentration and surface chemical concentration. When a chemical is above its solubility limit in the bulk (super saturated) elevated surface concentrations occur. Bloom can also be a nucleated phenomenon.

Friction Force of sliding or initiation of sliding between two surfaces. May be dominated by true contact area and van der Waals forces.

Adhesion Force of chemical, hydrogen or van der Waals bonding multiplied by area of contact. Meso scale design can increase area of contact to allow molecular level contact to occur.

Lubrication A fluid between two surfaces dramatically changes sliding friction. Meso scale roughness optimizes this behavior by controlling the flow regime and by reducing van der Waals adhesion.

Drag, flow control

Friction of a flowing liquid or gas over a surface. Meso scale features interact with a boundary layer of fluid to control onset of turbulence or point of separation of turbulent flow from a surface.

Heat Transfer Radiant heat transfer is a function of surface area. Convective heat transfer is dominated by boundary layer flow. Boiling heat transfer is dominated by nucleation of boilng. All are meso scale effects.

Performance attribute

Description

Growth of cells Strongly influenced by meso scale structures. Structures can retard bio-film formation and anchoring of species; or, provide a three dimensional environment promoting adhesion and inter-cell chemical communication.

Crack initiation,Weathering, UV, ozone

Reactive species such as ozone, UV rays and reactive species typically penetrate into the meso scale and cause structural damage. Local defects and stress concentrations at the meso scale can lead to crack initiation.

Properties of a Surface

“Engineering Touch”A surface’s physical structure and interaction with human sense

receptors has a tremendous impact on the perception of touch, feel and taste

• Concept of “engineering touch”: • Creating a surface that has a specific look and feel • Also exhibits other desirable characteristics such as low adhesion or super-hydrophobicity

Surface Tension• Some performance attributes

such as surface tension are controlled by both molecular and meso scale effects

• Interfacial surface tension is controlled at the molecular level: determines whether the material pair tend toward wetting (hydrophilic) or non-wetting (hydrophobic)

• Meso scale structures can amplify the natural tendency of the surface by changing the force balance at the interfaces

Contact Angles

• A droplet resting on a solid surface and surrounded by a gas forms a characteristic contact angle θ.

• Wenzel State: Rough solid surface, the liquid is in intimate contact with the solid asperities

• Cassie-Baxter State: the liquid rests on the tops of the asperities

It is desirable to achieve the Cassie-Baxter state because the droplets are significantly more mobile

Highly Hydrophobic Surfaces

• Problem today: a highly hydrophobic surface requires the use of expensive fluorine based compounds

• A super-hydrophobic surface can be created by a combination of:• Processes that create a

distribution of sizes and shapes of meso scale structures, randomly

distributed over a surface • Chemical modifications or

coatingsPTFE Polymer

There Exists No Low Cost Alternative to PTFE to Achieve Super-

hydrophobicity• There are alternative ways

to make a surface superhydrophobic.

• However, conventional efforts rely on fluoro compounds that: • Are expensive • Require special

procedures to protect environment and health

• Are time consuming • Require specific

processing conditionsSilicone rubber

Chemical Coatings for Super-hydrophobicity

• A number of paints and sprays currently in development attempt to mimic the “Lotus effect” by providing super-hydrophobic properties.

• In general, these compounds combine nano-particles with hydrophobic polymers such as waxes and plastics, and they form a nanostructure by a self-organization process during drying.

• While steps are taken to make them as safe as possible, these materials all contain some quantity of volatile organic compounds (VOCs).

Chemical Coatings for Super-hydrophobicity

Advantages Disadvantages

Easy to apply, re-applicable Expensive

Provide functionality on a limited number of material surfaces

Can be rubbed off easily - limited life on elastic, flexible surfaces

Often are slippery, have low coefficient of friction

Can be deactivated/removed by detergents

Wear out with time

May require significant regulatory approval

Super-hydrophobicity Without Coatings

• All coating solutions are indirect: they achieve hydrophobicity without physical structure modification.

• Engineering surface microstructures can allow ordinary materials such as aluminum, polyolefins and dienic rubber to compete with hydrophobic PTFE surfaces

What other methods engineer surfaces?

Laser and Micro-machining Technologies

• These technologies are commercial methods for generating microstructures, but:

• They create features one at a time and are slow

• Costs of $300 to $1000 per square cm are common for features of about 100 micron size. Costs rise quickly as feature size decreases

‘s Micro-molding Technology

Santoprene 63x

• Can create microscopic features on curved metal, polymer, ceramic, or organic surfaces.

• Advantages over competitive solutions: inherently lower cost, more environmentally friendly, and offers a greater degree of flexibility so that surfaces can be designed for specific applications. ETFE 20x

4. Applications

History of the Company

• Prof. King began the research prior to 2003.

• A major automotive manufacturing company sponsored research with Prof. King beginning in 2006 and continuing today.

• This highly successful work lead to trials in an industrial facility and fabrication of full sized prototypes products.

• Organization of Hoowaki occurred in Sept. 2008 to accelerate commercialization.

• Hoowaki’s laboratory and pilot facility opened Feb. 2009.

• Four patents have been filed and Hoowaki is supplying development samples to help define commercial products.

How Do We Do It?Step 1: Understand customer requirements

Step 2: Design and engineer surface

Step 3: Silicon micro-fabrication

Step 4 to N: Proprietary replication steps

Step N+1: Polymer, metal or ceramic forming tools

Step N+2: Customer’s tooling

Final step: Customer end product

Hoowaki expertise #1

How Do We Do It?Process for micro-casting

metalMetal with 10 microndiameter holes. 400nm ridges from the Bosch process are viewable in the picture showing a single 25 micron hole

Metal pillars 50 micron diameter

and 100 micron tall

How Do We Do It? Process for micro-casting

polymers

How Do We Do It?Micro-cast metal used as an

embossing master

Silicone embossed by micro-cast metal

Opposite left: 5 micro L water droplet on flat silicone surface with contact angel of 92 degrees

Opposite right: :5 micro L water droplet on silicone embossed with micro-structured metal alloy with contact angle of 152 deg. The silicone pillars have a diameter of 10 micron, a pitch of 20 micron and a height of 15 micron

How Do We Do It?Process for micro-casting a metal

roller

How Do We Do It?Micro-cast metal rollers

Micro-cast metal roller showing 100 micron diameter holes 15 micron deep. The roller could be used to emboss sheets of polymer in a roll to roll process

Unique Ability to Design Multiple Scales

• Range of features possible allows microstructures of varying size and dimensions to simultaneously perform different functional attributes.

• Further enhances the ability to engineer surfaces for specific applications.

• Features can be combined in ways no one has done before, such as creating a super-hydrophobic surface with high grip that has wonderful appearance and feel.

Micro-molding for Multifunctional Products

• Product designers may choose micro molding technology to adjust surface functionality and choose base materials for other functionality.

• Coatings and random surface texture processes have great difficulty to independently control different performance functions.

• The ability of micro molding technology to independently control hydrophobicity and friction coefficient is just one example of its large market potential

Micro-molding to deliver multifunctional products

Attribute 1 Attribute 2 Example Applications

Super hydrophobic High friction coefficient

Super hydrophobic Low friction coefficient

Super hydrophobic High cyclic loads

A few possible combinations…

Adjustable Multifunctional Parameters

• Height / Depth

• Width

• Angle

• Volume

• Shape

• Distance between structures

• Connectivity

• Surface Tension

• Friction, Grip

• Stiffness, Flexibility

• Wear Resistance

• Appearance

• Touch

• Surface Storage Volume

Advantages of micro-molding technology

• Inherently lower cost than competitive solutions

• Scalability of process

• Seamless integration with existing manufacturing facilities

• Environmentally friendly – no chemicals are used

• Can apply microstructures to metal, polymer, ceramic, or organic surfaces

• Applicability to curved surfaces

Disadvantages of micro-molding technology

• Doesn’t apply to extruded products such as textiles.

• Microstructures may change optical properties.

• Does not apply to materials that cannot be molded, imprinted, forged or deformed.

Creating products with engineered surfaces

Adapting the process for creating products with engineered

surfaces (cont.)

• Second process enhances the surface performance to boost product performance

• Requires unique know-how, tooling and intellectual property

• Engineering the surface may include modeling and computation of a variety of engineering parameters such as load, stiffness, surface tension or shrinkage.

• Design of a surface may include computer-aided design (CAD) in two and three dimensions to optimize look and feel and manufacturing integration.

Micrographs of representative materials

Micro Structured Curved Metal Surface 75X

Micro Structured PDMS Polymer

Surface 63X

Micro Structured Ceramic Surface

Cold forged 50, 30, 20, 10 micron dia. microstructures on aluminum foil (63x)

3. Hoowaki’smicro-molding technology

4. Applications

Applications of Hoowaki technology

Ice Mitigation

Drag Reduction

Self Cleaning

Preventing ice-build up

Self-cleaning surfaces

Reduced water drag

Reduced air drag

Improved grip

Touch and Feel

4. Applications

Working with Hoowaki• Purchase developmental micro-

molding tools, mold inserts, materials samples

• Joint development projects (Hoowaki) or basic research (UIUC)

• Share expertise

• Joint marketing: promotion of Hoowaki technology to upgrade materials into new markets

4. Applications

5. Discussion

Contact Information

To learn how your surfaces can be transformed, please contact:

Ralph Hulseman, President Hoowaki, LLC

RalphHulseman@Hoowaki.com 864 238-5631or Doug Wilson, VP Business DevelopmentDougWilson@hoowaki.com 704-425-3614

transforming surfaces

hoowaki overview linked inv2

mesoscale structures

meso scalemeso scale

meso scale18

meso level10

bulk materialssuch properties

surface microstructures

chemical scalebulk scale

movable objectsmolecular

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