This technique uses no electronic components to bring the cantilevers into contact with the substrate surface.

Researchers from North Carolina State University have developed a new
nanolithography technique that is less expensive than other approaches and can be
used to create technologies with biomedical applications.

“Among other things, this type of lithography can be used to manufacture
chips for use in biological sensors that can identify target molecules, such as
proteins or genetic material associated with specific medical conditions,” says
Albena Ivanisevic, co-author of a paper describing the research. Ivanisevic is
an associate professor of materials science and engineering at NC State and
associate professor of the joint biomedical engineering program at NC State and
the University of North Carolina at Chapel Hill. Nanolithography is a way of
printing patterns at the nanoscale.

The new technique relies on cantilevers, which are 150-micron long silicon
strips. The cantilevers can be tipped with spheres made of polymer or with
naturally occurring spores. The spheres and spores are coated with ink and
dried. The spheres and spores are absorbent and will soak up water when exposed
to increased humidity.

As a result, when the cantilevers are exposed to humidity in a chamber, the
spheres and spores absorb water—making the tips of the cantilevers heavier and
dragging them down into contact with any chosen surface.

Users can manipulate the size of the spheres and spores, which allows them
to control the patterns created by the cantilevers. For example, at low
humidity, a large sphere will absorb more water than a small sphere, and will
therefore be dragged down into contact with the substrate surface. The small sphere
won’t be lowered into contact with the surface until it is exposed to higher
humidity and absorbs more water.

Further, the differing characteristics of sphere polymers and spores mean
that they absorb different amounts of water when exposed to the same humidity—giving
users even more control of the nanolithography.

“This technique is less expensive than other device-driven lithography
techniques used for microfabrication because the cantilevers do not rely on
electronic components to bring the cantilevers into contact with the substrate
surface,” Ivanisevic says. “Next steps for this work include using this
approach to fabricate lithographic patterns onto tissue for use in tissue
regeneration efforts.”

The paper was published online in Small.

Source: North Carolina State University