A research team from the University of California, Berkeley, has reported developing NanoPen, an innovative and accessible technique that could prove especially useful in laying down patterns of nanoparticles for conveniently manufacturing miniaturized electronics with great speed and accuracy.
A number of so-called 'optical tweezer' techniques for laying down nanoparticles in precisely defined patterns already exist but, as pointed out by the team in a paper published in the latest edition of the journal Nano Letters, they typically need complex instrumentation and take up to a few hours to yield a satisfactory result.
But an even bigger issue with today's nano-patterning technology is that such techniques often risk damaging the particles being manipulated due to the high energy levels involved, which severely limits the range of their possible applications.
At Gizmag, we have recently looked at sound tweezers, a technique that harnesses sound rather than light for laying down tiny particles into regular patterns. However, unlike sound tweezers, the process developed by the Berkeley team also makes it easy to position tiny particles in an arbitrary fashion.
The NanoPen still uses light to position particles, but it can operate under much lower lighting conditions, reducing both energy consumption and the risk of damaging the particles.
"Since NanoPen is a light-induced patterning technique, it can be used for dynamic and flexible patterning of nanoparticles by adjusting the projected light pattern using a spatial light modulator," lead author Dr Ming Wu explained in the paper.
"Moreover, the low required optical power intensity for actuation of NanoPen makes it possible to pattern the nanostructures using a commercial projector (Dell, 2400MP with 3000 ANSI Lumens, 1024 × 768 resolution) with <10W/cm2 optical intensity."
The team demonstrated this capability by patterning gold particles 90 nanometers in diameter (see picture above). These arbitrary patterns were created by interfacing Microsoft PowerPoint with the projector. The patterns were then focused onto a custom chip using a 20× objective, with an exposure time of only two minutes.
The process does, however, require the use of special 'photoconductive' surfaces. According to Wu, manufacturers can adjust the size and density of the patterns simply by changing the voltage, light intensity, and exposure time applied during the process.
Leaving faraway and hard-to-predict future nanotech applications aside, the NanoPen could find immediate use in medical diagnosis — where it is often vital not to damage the cells being manipulated — sensing and solar cell technology, to mention a few.
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