Rapid Prototyping has established itself over the last decade as a powerful tool for quickly generating complex models and prototypes (e.g., Fig. 1) on the macroscale.

Rapid Prototyping offers:

• Virtually arbitrary 3-D geometry; short lead times
  
• Fully-automated, unattended processing
  
• A single, self-contained machine (e.g., Fig. 2) that produces an enormous variety of shapes
  
• Manufacturing cost that is largely independent of complexity
  
• High repeatability (few process variables)
  
• Easy device design (few manufacturing constraints)
  

A wide variety of rapid prototyping processes have been developed, and many are in commercial use. EFAB uses a new process, since none of the earlier processes are well-suited to batch fabrication of microstructures:

• Intended for producing macroscopic parts, they cannot produce features less than 50-100 microns in width, or layers less than 50-150 microns thick
  
• Virtually all existing processes generate a layer serially (one volume element at a time), so are too slow and costly for quantity production
  
• Many rapid prototyping materials do not allow functional use, due to intrinsic properties or porosity
  
• Some rapid prototyping processes (e.g., stereolithography) do not produce net-shape structures, but require support structures composed of structural material that must be removed from each device (not feasible for micro-devices, especially if made in the millions)

Stereolithography, Selective Laser Sintering, Thermojet (3D Systems)

Fused Deposition Modeling (Stratasys)

3-D Printing (MIT, Soligen/PartsNow, Z Corporation, ProMetal)