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What is Nanotechnology – Nano and Micro – Lithography , Molecular/Chemical Nanotechnology

Scientists  have  discovered  that materials  at small dimensions—small particles,  thin  films,  etc—can  have significantly  different  properties  than  the same materials  at  larger  scale.    There  are  thus  endless  possibilities  for improved devices, structures, and materials  if  we  can understand these  differences, and learn how  to  control  the assembly  of  small structures.   There  are many  different  views  of  precisely  what  is  included in nanotechnology.  In  general,  however, most agree  that three  things  are  important:

1.  Small  size, measured in  100s  of  nanometers  or  less 
2.  Unique properties  because of  the small  size 
3.  Control  the  structure  and  composition on the  nm  scale  in order  to control  the  properties. 

Nanostructures—objects  with  nanometer  scale features—are not  new  and  they  were not  first  created  by  man.   There  are  many  examples  of  nanostructures  in nature  in the  way  that  plants  and animals  have  evolved. Similarly there are  many  natural  nanoscale materials,  such  as  catalysts,  porous  materials,  certain  minerals,  soot  particles, etc.,  that  have  unique  properties  particularly  because  of  the  nanoscale  features.  In the  past  decade, innovations in our  understanding  of  nanotechnology  have  enabled us  to begin to  understand and control  these  structures  and properties  in order  to  make new  functional  materials  and  devices.    We have entered  the era of  engineered nanomaterials  and  devices.

Nano- & Micro-lithography:  “Top-Down  Nanotechnology”
An  area  of  nanotechnology  that  has  been evolving for  the  last  40  years  is  the  technique  of micro-  and    nanolithography  and  etching.  These techniques  are  the  source  of  the  great microelectronics  revolution,     sometimes called  “top-down”  nanotechnology.     Here,  small  features  are  made  by  starting  with  larger  materials  and patterning  or  “carving  down” to  make nanoscale structures  in precise  patterns. Complex  structures  such  as microprocessors  containing  hundreds  of  millions  of  precisely  positioned  nanostructures  can  be  fabricated.   Tthis is  the  most well-established  of all  forms  of nanotechnology.  Production machines  for  these  techniques  can cost millions  of  dollars  and a  full-scale microprocessor  factory  can  cost  a  billion  dollars  or more.    In recent  years, the same  “top down”  nanoprocessing  techniques  have  enabled many  non-electronic applications, including micromechanical,  microptical,  and  microfluidic  devices.                  

Molecular/Chemical Nanotechnology:
“Self-Assembly” Often  called  molecular  or  chemical  nanotechnology, this  fundamentally  different  area  of  nanotechnology  results from starting  at the  atomic  scale  and  building  up  materials  and  structures,  atom by  atom.    It is  essentially molecular  engineering.     This  is  accomplished  by  utilizing  the forces  of  nature to  assemble nanostructures  –  the term “self assembly” is often used.  Here the forces of chemistry are in control and we have, at least to date,  somewhat less  flexibility  in  making  arbitrary  structures.  The  nanomaterials  created  this  way, however, have resulted in a  number  of  consumer  products. Significant  advances  continue,  the  more  we  explore  and  understand the area of  chemical  nanotechnology. In  addition, there  are  many  exciting  applications  that combine  both bottom-up and top-down processing. An example  of  this  would be  single-molecule  transistors  that  have  large (macroscopic)  leads  fabricated  by  topdown  as  well  as  single  molecule  (microscopic)  assemblies  built  from  the  bottom,  up.

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