Nanotechnology is getting closer to 3D-nanoprinting

Fabrication of three-dimensional (3D) objects through direct deposition of functional materials – also called additive manufacturing – has been a subject of intense study in the area of macroscale manufacturing for several decades. These 3D-printing techniques are reaching a stage where desired products and structures can be made independent of the complexity of their shapes – even bioprinting tissue is now in the realm of the possible. Applying 3D-printing concepts to nanotechnology could bring similar advantages to nanofabrication – speed, less waste, economic viability – than it is expected to bring to manufacturing technologies. In addition, pre-patterned micro- or nanostructures could be used as substrates, allowing researchers to realize unprecedented manufacturing flexibility, functionality and complexity at the nanoscale. Researchers in Korea have now shown that nanoscale 3D-objects such as free-standing nanowalls can be constructed by an additive manufacturing scheme. Even without the motion of the substrate, nanojets are spontaneously laid down and piled to yield nanowalls.The team, led by Ho-Young Kim, a professor at Seoul National University, explain their findings.

"Electrospinning that produces polymer nanojets is a relatively simple and inexpensive method to yield nanoscale fibers, but the fiber streams are so chaotic that control of individual fibers has been considered almost impossible," Kim explains. "In our recent work, we have shown that an electrospun polymer solution jet, which tends to become unstable as traveling in the air due to Coulombic repulsion, can be stably focused onto a thin metal electrode line. "Kim and his team also elucidated the fundamental electromechanical mechanism that enables the spontaneous stacking of a nanofiber onto itself to provide a physical basis behind this novel nanofabrication process. In this novel method, a thin metal line on an insulating plate strongly focuses the electrical field, thus the whipping instability of the electrical nanojets is suppressed.

The construction of a free-standing nanowall is the most fundamental step to achieve 3D-nanoprinting. This process is so attractive because it needs only a power supply and a linear stage to build free-standing nanowalls after drawing metal microlines, all of which can be conducted under normal laboratory conditions. Kim points out that this technique has a significant economic advantage as compared to conventional nanomanufacturing processes used to build nanowalls such as DRIE (deep reactive ion etching).

"Full 3D-control of an electrospun nanojet would possibly revolutionize the current nanofabrication technology, which we aim to achieve in the long run," says Kim. "However, we believe that such great achievement cannot be made with a single step. Further development for the precise control of the nanojet could realize full 3D-nanofabrication."

(http://www.nanowerk.com/spotlight/spotid=34275.php)