3D microfabrication

3D Microfabrication relates to the engineering of bulk solids on the micrometre or submicrometre scale. Although the term nanofabrication might be considered for the submicrometre scale, it is not in common use, and tends to relate to a bottom-up approach (while microfabrication more often uses top-down approaches). Simple surface treatments, or substantially two-dimensional methods, (such as lithography and chemical vapor deposition) are not considered to be 3D methods. Conceptually, a 3D microfabricated object should be created with three-dimensional resolution and can ideally be freely manipulated (i.e. can be fabricated without any necessary attachments to substrates).

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Techniques of microfabrication

Several radically different approaches to 3D microfabrication are under development.

Semiconductor fabrication methods

Although most semiconductor wafer-based microfabrication does not truly qualify as 3D in this sense, the processes used can certainly be leveraged to create 3D microfabricated objects, for example:

• Chemical vapor deposition
• Photolithography
• Electron beam lithography

See also: microfabrication; bulk micromachining; surface micromachining

Printing methods

Many groups are investigating the possibility of creating 3D objects by building up layer upon layer of material by printing methodologies. This approach is already used successfully on larger scales for rapid prototyping. Techniques include:

• Inkjet printing
• Microcontact printing

See also: 3D printing

2-photon polymerization

In the 2-photon polymerization method, a block of gel containing various monomers and a photoinitiator is irradiated with a focused laser, which traces the 3D profile of the object to be created. The laser light initiates polymerization, but only at the focal point as a result of the nonlinear nature of the excitation. The laser passes unperturbed through both polymerized and unpolymerized regions of the material. After this tracing is finished, the object may be recovered by washing away the unpolymerized gel with common organic solvents. Objects with feature sizes of less than 100 nanometers can easily be created. [1]

See also: 3D optical data storage

Self-assembly

Techniques of self-assembly and self-organization have been exploited by scientists such as George Whitesides to create micrometre-scale objects and devices.

Applications of 3D microfabrication

• Micromachinery
• Prototyping
• Waveguides and other custom optics