Since Professor Richard Feynman’s timeless lecture “There's Plenty of Room at the Bottom” where he envisions the creation of nano-machines, electron microscopes and even a minuscule doctor to be swallowed by the patient, the broad field of nano-science has achieved impressive progress. Yet, the challenge of defining and shaping nanoscopic structures to harness the remarkable properties of nanomaterials remains as current as ever.
This challenge has been addressed by the Oxford team, in their latest publication “Exploiting rotational asymmetry for sub-50 nm mechanical nanocalligraphy” published in the journal of Microsystems and Nanoengineering.
Taking a calligraphy-based approach, but this time at nanometre-size scales, the team have circumvented the resolution bounds imposed by state-of-the-art nanolithography processes to make it theoretically possible to pattern and shape atomically thin structures with high throughput and at an extremely low cost. This technique entitled nano-calligraphy scanning probe lithography (nc-SPL) is based on the observation that control over the writing angle in calligraphic writing can produce a continuum of line-widths. This observation has been exploited using two types of “writing” tips at the nanoscale – one a flat tip familiar to calligraphers and the other an improvisation of this using a double probe system. The writing direction is then controlled to achieve spacing between adjacent lines to under 50 nanometres.
But how does one showcase this technique that achieves such small patterns in dimensions smaller than 100 times that of a human hair, a size far too difficult for the human eye to discern? By forming a collaboration with world-leading calligraphy artist Majid Alyousef. Doctoral student and lead author, Nickolaos Farmakdis masterminded the collaboration to showcase the capabilities of nc-SPL by reproducing Alyousef’s complex calligraphic artwork.
Farmakidis says, “As the scales of phenomena are reduced to nanoscopic dimensions, a fundamentally different and often counterintuitive set of rules applies. Even so, borrowing concepts from the tangible world can inspire ideas which can be adapted to the peculiarities encountered at the nanoscale. Here for example we have borrowed an artistic concept and translated it into a powerful scientific tool.”
Artist Alyousef comments: “The idea that calligraphy can be produced at such a small scale is fascinating. This is an ancient artform that uses traditional tools and a specific pen nib. The fact that this can be replicated in the nano-world made this project so exciting and challenging.”
One requirement of the technique is the asymmetric tips in the shape of a ‘chisel’ or ‘double tip. The authors created these by employing a focused ion beam to directly sculpt the required profiles out of silicon.
Harish Bhaskaran, senior author of the paper adds: “Engineers have always used the tools of science to create innovations, but this work uses concepts from the arts world to create a technique that leads to nanoscale patterning. It achieves the possibility to not only create really small features, but also vary the width of these features continuously and smoothly as required for photonic chips. We love this in the group and the challenge to reproduce Majid’s amazing art energized our research.”
How can this technique add to the broad field of nanoscience? Farmakidis explains: “nc-SPL will enable the use of non-traditional lithography processes in manufacturing computer chips with dimensions – especially gaps between features – smaller than what one can achieve otherwise. The technique could be combined with other forms of mechanical lithography across all size scales, inspiring chips with a range of dimensions and continuously varying linewidths in future.”
The paper has inspired an arts blog by the group’s Artist in Residence, Meadhbh O’Connor, entitled “On Mark Making: An Artist’s impression from inside Oxford’s Bhaskaran Lab.”