Molecular Manufacturing Challenges

CRN's Chris Phoenix was asked by the U.S. National Academy of Sciences to prepare briefing papers for their recent committee sessions investigating molecular manufacturing. So far, we've posted Concepts of Molecular Manufacturing, Current Status of Molecular Manufacturing, and Applications of Molecular Theory.

Today's entry is Molecular Manufacturing Challenges:

The core of molecular manufacturing is the mechanical control of molecular structure building. This has almost been achieved today by several methods, both "top-down" and "bottom-up." Seeman's DNA-building machine can be programmed to create any of several sequences. Scanning probe microscopes have been used to break and form selected covalent bonds between molecules, and in Japan both STM and AFM have removed and replaced single atoms at selected locations in covalent crystals.

A major goal of molecular manufacturing is building nanoscale tools that are small and flexible enough to build duplicate tools rapidly. Bottom-up technologies appear to be closer to that goal. Their speed and flexibility would need to be increased, but a polymer-based tool that could (perhaps assisted by self-assembly) build its polymer components appears to be within reach.

Top-down approaches should not be ruled out. Scanning probe systems have been built in MEMS technologies. If a nanoscale version could be designed, it might be built by any of several nanoscale fabrication methods. Further work with covalent solids (e.g. silicon, silica, diamond, alumina, cubic boron nitride) in either solvent or vacuum might show a way to build general 3D structures with scanning probe molecular manufacturing; this could allow one scanning probe to build a duplicate.

Bottom-up tools include protein design, DNA design, and several related polymer systems (see work by Seeman, and Schafmeister), which can make precise engineered 3D structures. Top-down tools include electron beam induced deposition, two-photon polymerization, ion beam milling, and e-beam lithography. Typical feature size is 10 nm, though ion beam may approach single-atom precision.

Barriers to advancement of molecular manufacturing are largely perceptual at this point. The use of mechanical nanoscale systems for exponential manufacturing has been prematurely criticized, resulting in widespread perception that the approach is a dead end. General acceptance that the technology may have significant potential would substantially accelerate its development.

Basic molecular manufacturing—building molecular structures under mechanical control—has nearly been achieved, though not developed. Exponential manufacturing could be demonstrated in a polymer system with modest effort. Several research directions could extend the utility of that. Nanoscale mechanical engineering, especially friction and classical approximations, should be better understood. Faster actuators could be developed and integrated. Stronger materials could be achieved either by crosslinking or by building covalent solids. The ultimate step is to integrate multiple nanoscale manufacturing systems. This would require research into nanoscale computers; fastening systems for nanoscale products; nanoscale and mesoscale structure; reliability and control; additional mechanical engineering (for ease of design); and product design methodologies.

Tomorrow: "Impacts of Molecular Manufacturing"

Comments

[todd]

I was actually going to request some additional information today. As I am sure many of you read this I wonder what else everyone is reading. There are numerous links to other web pages listed on CRN's homepage. Perhaps we could or someone could comment on the top 10 current locations for information pertaining to molecular manufacturing. I'm sure I could list three or for myself notwithstanding this web page. But I was hoping for some new sites that someone else has seen that give some new information pertinent and relevant to the subject at hand.

Thanks again
Todd

[Philip Moriarty]

Todd,

Try Soft Machines for a physicist's take on whether molecular manufacturing "has almost been achieved today"....

Philip

[Mike Treder, CRN]

Todd, I'm not sure if this is the page you were referring to from our site, but we have many useful links here.

[todd]

vary nice :) thanks this will take some time to review