Lower cost molding of Microstructures at the millimeter to micron scale

They have made 5 micron pillars on copper

The Society of Manufacturing Engineers (SME) has selected Hoowaki, LLC as one of the seven recipients for the 4th Annual SME List of Innovations That Could Change the Way You Manufacture.

The award was presented for Hoowaki’s surface engineering technology that increases energy efficiency by improving friction, fluid drag and heat transfer. This innovation comes from the laboratory of William King, Chief Technology Officer of Hoowaki and Professor of Mechanical Science and Engineering at the University of Illinois. “Microstructures molded onto a surface can change the properties of that surface,” says King. “By molding microstructures into a surface, we can engineer the surface friction, heat transfer coefficient, or water repellency. All of these are in demand for energy efficiency applications, from hydraulic equipment to air conditioners to batteries.”

Different patterns on copper

Hoowaki has developed a unique surface molding technology to unleash the engineering potential at the meso scale. Here the meso scale is defined as smaller than what the unaided eye can see, or about 0.2mm, down to about a micron. Properties of surfaces differ from those of bulk materials and strongly influence many of the performance characteristics that contribute to product value.

160 micron holes in stainless steel

Benefits of Hoowaki Process

* Low cost – our proprietary micro-molding process forms millions of tiny surface features at once and has a clear route to low cost scale up

* Processing flexibility – Hoowaki tooling can be used in a number of industrial processes including injection molding, compression molding, roll processing, extrusion, stamping, forging and casting.

* Process integration – microstructures can be applied to existing tooling through direct machining methods.

* Design flexibility and expertise – Hoowaki is able to engineer surface patterns tailored to specific applications to modify surface properties independent of the bulk material properties. Multiple “levels” of features give combinations of surface performance attributes never before possible. Hoowaki has the unique ability to form micro patterns on both flat and curved parts out of metal and other

Casting metal microstructures from a flexible and reusable mold

This paper describes casting-based microfabrication of metal microstructures and nanostructures. The metal was cast into flexible silicone molds which were themselves cast from microfabricated silicon templates. Microcasting is demonstrated in two metal alloys of melting temperature 70 ◦C or 138 ◦C. Many structures were successfully cast into the metal with excellent replication fidelity, including ridges with periodicity 400 nm and holes or pillars with diameter in the range 10–100 μm and aspect ratio up to 2:1. The flexibility of the silicone mold permits casting of curved surfaces, which we demonstrate by fabricating a cylindrical metal roller of diameter 8 mm covered with microstructures. The metal microstructures can be in turn used as a reusable molding tool.

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