Nanotechnology: Top Down or Bottom Up?
How our knowledge of nanoparticles should be used has been a subject of much debate. Nanotechnologists have offered two approaches for fabricating materials or manipulating devices using nanotechnology: top down and bottom up.
Imagine you need to build the tiniest computer chip possible. Using the bottom-up approach, you would use nanotechnology to assemble the chip atom by atom, placing each type of atom in a specific location to build the circuit.
With the top-down approach, you would instead create the computer chip by carving away at bulk material — much like a sculptor and his artwork — to create nano-sized features, never dealing with the atomic level of matter.
The top-down method is currently in use to manufacture computer chips as well as other products you use every day. The bottom-up method is in the theoretical stage, with researchers doing initial experiments to develop these techniques.
Nanotechnologists also use a technique called self-assembly to build structures using nanoparticles. Self-assembly involves creating conditions such that atoms and molecules arrange themselves in a specific way to create a material. Some consider this one form of the bottom-up approach.
Mihail (Mike) Roco of the Nanotechnology Initiative has suggested that nanotechnology development will occur in four generations.
Currently, according to Roco, we’re in an era of passive nanostructures, which he describes as materials designed to perform one task.
In the second generation, which we have already entered, we are using active nanostructures for multitasking. These nanostructures would include devices to deliver drugs in a targeted way.
The third generation would include nanosystems that might involve thousands of components interacting with each other.
Finally, several years in the future, we may see integrated nanosystems, including systems within systems that could accomplish far more than we can today, such as sophisticated molecular manufacturing of genes inside the DNA of targeted cells and nanosurgery for healing wounds on the cellular level.