Building 3-D fractals on a nanoscale: Structure repeats itself from micro to nano

Jun 19, 2013

It all starts with a single octahedron structure, then after four iterations there are already 625 of them. Each iteration creates a new octahedron at each vertex. The result is a fascinating 3D fractal construction on micro and nanoscale, suitable e.g. for high-performance filters. Researchers at the University of Twente's MESA+ Institute for Nanotechnology present this invention in the Journal of Micromechanics and Microengineering.

A geometrical figure can repeat itself ad infinitum in a fractal. As you zoom in you keep seeing the same . The big advantage of a three-dimensional fractal is that the effective surface area increases with each diminution and at the same time the space is used to the full. In the case of the octahedrons the final structure is not much larger than the original octahedron but the effective surface area has grown by a factor of 6.5. The smallest octahedra are 300 nanometres in size with at the vertices 100 nanometres in diameter. 625 of these nanopores on a small area can create a highly effective filter with very low , for example. The octahedra can also be used as tiny cages to hold living cells and examine their interactions with cells in neighbouring octahedra. And what happens if you direct light into the structure? The possibilities are legion.

Corner lithography

In order to create the repetitive three-dimensional structure the researchers use a technology which they have developed themselves, known as 'corner '. First a pyramid shape is etched into silicon, then a of silicon nitride is applied. This is removed, leaving a tiny amount of silicon nitride in the vertices, a sort of plug. This too is removed so that more etching can take place through the hole thus created. The octagonal 3D structure forms of its own accord along the crystalline planes of the silicon by 'auto-alignment'.

Building 3-D fractals on a nanoscale: Structure repeats itself from micro to nano

is again applied to each and the process is repeated. The new structure automatically unfolds in each direction, with the size of the new octahedra depending on the etching time. The structure thus develops from micrometres to nanometres. One of the big advantages is that no complex technology is needed to make the pores one by one, for example. Millions of the fractals can be created in parallel on a wafer, each with 625 pores. More than four iterations can be employed, but this does places greater demands on the technology and the precision of the etching process.

The research was conducted by the Transducers Science and Technology Group of the University of Twente's MESA+ Institute for Nanotechnology.

The article, 'Fabrication of 3D fractal structures using nanoscale anisotropic etching of single crystalline silicon' by Erwin Berenschot, Henri Jansen and Niels Tas, is on the cover of the May issue of the Journal of Micromechanics and Microengineering.

Explore further: Building 3-D fractals on a nano scale

More information: stacks.iop.org/JMM/23/055024

Related Stories

Building 3-D fractals on a nano scale

May 31, 2013

It starts with one 3D structure with eight planes, an octahedron. This repeats itself to smaller octahedra: 625 after just four steps. At every corner of a new octahedron, a successive octahedron is formed. ...

Team develops method for creating 3D photonic crystals

Nov 07, 2011

Dutch researchers at the University of Twente's MESA+ research institute, together with ASML, TNO (the Netherlands Organisation for Applied Scientific Research) and TU/e (Eindhoven University of Technology) ...

Capturing living cells in micro pyramids

Nov 22, 2012

A field full of pyramids, but on a micro scale. Each of the pyramids hides a living cell. Thanks to 3D micro- and nano scale fabrication, promising new applications can be found. One of them is applying the ...

Recommended for you

Thinnest feasible nano-membrane produced

14 hours ago

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

17 hours ago

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Six Nepalese dead, six missing in Everest avalanche

At least six Nepalese climbing guides have been killed and six others are missing after an avalanche struck Mount Everest early Friday in one of the deadliest accidents on the world's highest peak, officials ...

White House updating online privacy policy

A new Obama administration privacy policy out Friday explains how the government will gather the user data of online visitors to WhiteHouse.gov, mobile apps and social media sites. It also clarifies that ...