Computer Aided Design (CAD) that works at the atomic level is relatively new and yet very primitive.

The first step researcher’s have taken toward digital nanofabrication is starting out with basic computer aided design (CAD) programs and building nanostructures. Geoff Leach from the Royal Melbourne Institute of Technology discusses the advancements made in molecular nanotechnology using a CAD program. “Molecular nanotechnology requires CAD tools to design components, subsystems and systems. Moreover, the CAD tools must be tailored to the particular needs of molecular nanotechnology. One of those needs is for molecular CAD software to produce designs in full atomic detail––where the position of every atom is specified.” The CAD program made to meet these requirements is called “Crystal Sketchpad” (formerly know as Crystal Clear) and was written by Ralph Merkle and Eric Drexler. Crystal Sketchpad uses elements of mechanical CAD while also using elements of molecular modeling, which is based on diamondoid materials. The crystalline nature of these materials must be able to be read by the computer program, hence the name of the program. There are other similar programs such as Molecular Modelling Toolkit and NanoCAD, but many of these programs are very limited and rather primitive still. Another program called Molecular Assembly Sequence Software (MASS), designed by Carol Shaw. It can be used to view molecular nanotechnology designs in Protein Data Bank format and allows the user to rotate and zoom in on the atomic structure as well as disassemble it. Many programs are still currently being worked on and are used in nanofabrication labs such as MEMSPro, Spice, Fungimol and the Ansoft High Frequency Structure Simulator.

CAD for digital nanofabrication will somewhat resemble the CAD programs we have today, but their purpose will be very different. Current CAD programs use data to create digital objects and possibly run tests, but CAD programs for digital nanofabrication will serve as programming tools. Many scientist including , Prof. Hugo DeGaris from Utah State University, believe that programming molecules will be the only way to build large objects using digital nanofabrication.

It would take too long to build anything visible to the naked eye, using the “atom by atom” approach and it is thus necessary to create larger structures by simultaneous assemble. Simultaneous assembly with traditional methods will be extremely difficult due to two main factors. The number of microscopic “robotic arms” needed to assemble trillions of atoms will be enormous and the arms will in addition face great difficulties coordinating with each other. The arms will not only have to be on the nanoscale, but they must also place each atom at the correct spot, while taking into account the physical obstructions of other robot arms. Programmed molecules, on the other hand, will work very fast and bond with other programmed molecules to form the desired structures. We do, however, face one major problem with programming molecules, because we have neither the technology nor the theory. Some have suggested that we randomly program molecules and then choose the ones that have useful properties, but this approach seems too tedious to become a real possibility. Future research will hopefully give us a better understanding and enable us to successfully program molecules to perform specific tasks. There are still many years of research needed before we will have a complete enough understanding to program and predict molecular behavior, but without this knowledge, digital nanofabrication of large objects might never become a reality.

Sources:

http://www.carol.com/mass.shtml

http://goanna.cs.rmit.edu.au/~gl/research/nano/CrystalSketchpad/paper/html/nano95.html

http://www.cmf.rl.ac.uk/cad/memspro.html

http://www.aboutspice.com/details.php?ID=374

http://www.ansoft.com/products/hf/hfss/

http://www.nanomagazine.com/i.php?id=01_17_12