Xolographic Biology

[Image: Plankton via the Seattle Aquarium.]

The description of this new 3D-printing technique, published in Nature, is immensely evocative. The process “relies on chemical reactions triggered by the intersection of two light beams,” using that light “to rapidly solidify an object in a volume of a liquid precursor.”

Its developers call it xolography “because it uses two crossing (x) light beams of different wavelengths to solidify a whole object (holos is the Greek word for whole).”

But the whole thing sounds like some weird new metaphor for the origins of biology: light shining into susceptible chemistries in a warm little pond somewhere, synthesizing into slowly-growing forms. From the Miller-Urey experiment to photosynthetic 3D printing.

The ensuing mechanics are hardly poetic, but are nevertheless worth reading:

A rectangular sheet of light with a set thickness is shone through a volume of a viscous resin. The wavelength of the light is chosen to excite molecules known as dual-colour photoinitiators (DCPIs) dissolved in the resin by cleaving a molecular ring in the backbone of the molecule; this reaction occurs only within the sheet of light.

A second beam of light projects an image of a slice of the 3D object to be printed into the plane of the light sheet. The wavelength of the second beam is different from that of the first and causes any excited DCPI molecules to initiate polymerization of the resin, solidifying the slice. The resin volume is then moved relative to the position of the light sheet, which is fixed. This changes the position of the light sheet in the resin, so the activation and initiation processes can begin again at a new position, thereby building up the object slice by slice.

Forms emerging as if from nowhere, out of intersecting planes of light—or beams passing through one another in the shallow waters of a sea, materializing into bodies. Tiny little plankton drifting in the sun.

Anyway, to use such an interesting process simply to 3D-print new children’s toys or architectural parts seems both anticlimactic and strangely on par with our world, which is already so good at hiding interesting metaphors in the everyday objects around us.

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