For a smartphone display to produce moving, holographic 3D images, it needs to twist the light it emits. Now, researchers at the University of Michigan (UM) and Ben-Gurion University (BGU) of the Negev have found a way to mass produce spiral semiconductors that can take that important, light-coiling step.

UM researchers unveiled some of the first holographic images in 1962, made by coaxing waves of light to form an array of bright and dark spots in space. This creates a static illusion of a material object. To make these frozen waves, researchers encoded images onto a material that could control the direction (polarisation) and timing (phase) of the fluctuations within the electromagnetic waves.

The new semiconductor helices created by the team, led by UM researchers, offer that level of control over light in a format that could work in the pixels of displays. They can be incorporated into other semiconductor devices to vary the polarisation, phase and colour of light emitted by the different pixels, each of them made from the precisely designed semiconductor helices. This could one day enable moving holograms, projected by smartphones and other screens.

Until now, making semiconductors spirals with sufficiently strong twist—reminiscent of nanoscale fusilli pasta—was a difficult prospect because the twisted state is unnatural to semiconductor materials. They usually form sheets or wires. But Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering, and his team have found a way to guide the attachment of small semiconductor nanoparticles to each other with help from some of nature's twisted structures: proteins and DNA.

UM twisted semi 01 (cr) Figure 1: Wenchun Feng pipettes the red nanoparticle solution into small vials with methanol to precipitate the nanoparticles. (Source: Zhengzhi Mu, Kotov Lab)

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