Optical contact bonding

Optical contact bonding is a glueless process whereby two closely conformal surfaces are joined, being held purely by intermolecular forces.

However, if the bodies are conformal to an accuracy of better than 10 angstroms (1 nanometer), then a sufficient surface area is in close enough contact for the intermolecular interactions to have an observable macroscopic effect—that is, the two objects stick together.

[3] Such a condition requires a high degree of accuracy and surface smoothness, which is typically found in optical components, such as prisms.

For bonding to occur, the surfaces need only to be brought together; the intermolecular forces draw the bodies into the lowest energy conformation, and no pressure needs to be applied.

Typically, glues and binders are more heat sensitive or have undesirable properties compared to the actual bodies being joined.

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Gauge blocks wrung together and held horizontally. The blocks are held together solely by the adhesion of their extremely flat surfaces, which is so strong that it easily supports their weight.