MIT researchers have developed flexible, transparent silicon-photonics chips that could enable curved displays, wearable health monitors, and lighter optical systems for demanding new electronics applications.
MIT researchers, working with NY Creates, have developed flexible, transparent silicon-photonics chips that could bring advanced optical systems to curved displays, wearable health monitors, and other electronics applications.
The wafer-scale fabrication process addresses a long-standing limitation of silicon photonics. Conventional devices can integrate billions of nanoscale optical components on 300-millimetre wafers, but the resulting chips are typically rigid and opaque. Earlier demonstrations achieved flexibility or transparency separately, but were difficult to scale.
The new approach starts with conventional silicon-photonics fabrication, with tiny optical waveguides patterned onto a silicon wafer. A temporary silicon support is then bonded to the structure before the original substrate is removed. This leaves an ultrathin layer containing the oxide and waveguides. Researchers subsequently attach a transparent polyester film, producing a flexible wafer only a few microns thick.
Keeping the wafer intact during this process was a major engineering challenge. The team managed mechanical stress by using fabrication steps at temperatures of 500°C or below and carefully combining material-removal techniques. Industrial thinning methods were followed by selective chemical etching to remove the final silicon without damaging the optical layers.
Performance tests showed that the chips could be bent thousands of times around cylinders, including one roughly the width of a small screw, without measurable degradation. Transparency tests using a bionic eye also found minimal haze and little visible image distortion.
The technology could support curved augmented-reality displays, including heads-up displays and pilot visors, while potentially reducing the bulk of conventional optical systems. Flexible photonic chips could also conform to the body for discreet health monitoring.
The researchers plan to add more complex components, improve waveguide efficiency, and further increase transparency. The work could ultimately expand silicon photonics beyond rigid semiconductor packages into flexible, transparent electronics.
