Manufacturing Bits: Aug. 6

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Printing Ears
Engineered cartilage is an option for auricular reconstruction. Enabling the development of engineered cartilage, Massachusetts General Hospital has fabricated a bioartificial ear using a 3D printer technology. The ear looks and mechanically behaves like a human one.

Researchers used a titanium wire framework within a composite collagen ear-shaped scaffold to maintain the dimensions of the ear. Then, they combined the collagen from cows with ear cartilage cells from sheep. Following that step, researchers molded this into an ear using 3D printed scaffolds.

To test the technology, the ear was redesigned and implanted in a “nude rat model.” “This is the first demonstration of a full-size human ear that maintains shape and flexibility after three months,” said researcher Thomas Cervantes, on The Royal Society’s Web site. “Shape and flexibility are key; tissue engineered constructs tend to distort in shape during growth, which is obviously a problem for the ear, because we are aiming to recreate a very specific shape.”

Mona Lisa Lithography
Using a new lithography technique, Georgia Institute of Technology has painted the Mona Lisa on a substrate surface at 30nm feature sizes. Georgia Tech’s version of the famous painting is called the “Mini Lisa.”

Researchers created the image using an atomic force microscope (AFM) and a process called ThermoChemical NanoLithography (TCNL). Going pixel by pixel, researchers positioned the AFM at the substrate surface. Each pixel is spaced by 125nm. This, in turn, enabled a series of chemical reactions.

More specifically, the approach uses a heated cantilever to drive a chemical reaction. Researchers demonstrated a spatial resolution of 20nm, where the entire concentration profile is confined to sub-180nm. To control the images, researchers devised a chemical kinetics model. Researchers also designed 2D temperature maps for the linear and nonlinear gradients.

“By tuning the temperature, our team manipulated chemical reactions to yield variations in the molecular concentrations on the nanoscale,” said Jennifer Curtis, an associate professor in the School of Physics, on Georgia Tech’s Web site. “The spatial confinement of these reactions provides the precision required to generate complex chemical images like the Mini Lisa.”

Georgia Tech recently integrated nanoarrays of five thermal cantilevers to accelerate the pace of production. “We envision TCNL will be capable of patterning gradients of other physical or chemical properties, such as conductivity of graphene,” Curtis said. “This technique should enable a wide range of previously inaccessible experiments and applications in fields as diverse as nanoelectronics, optoelectronics and bioengineering.”

Ion Imprint Litho
HP Labs, the University of Hong Kong and the University of Southern California have disclosed more details about their ongoing research to combine helium ion beam lithography with nanoimprint lithography. With the two technologies, researchers see a path towards sub-10nm devices, perhaps even 4nm.

At present, a traditional electron-beam is used to make the master pattern or template for the nanoimprint lithography process. But e-beams are slow and the resolutions are not generally fine enough for sub-10nm work.

Scanning electron microscopy images of 4nm half-pitch lines (a) patterned in HSQ using HIBL and (b) transferred into UV nanoimprint resist. Source: SPIE

Instead of e-beams, researchers are looking at helium ion microscopes. In this system, helium ions are focused at a small spot size. This, in turn, could make it a promising tool for use in devising sub-10nm arbitrary patterns on nanoimprint templates.

Researchers recently demonstrated the technology using Carl Zeiss’ helium ion scope with a pattern generator on a 12nm hydrogen silsesquioxane (HSQ) resist, which was spin-coated on a silicon substrate. With the technology, the smallest line patterns demonstrated were 4nm. Using the HSQ patterns as a nanoimprint template, patterns down to 4nm half-pitch were transferred into nanoimprint resist through a UV-curable nanoimprint process.

—Mark LaPedus