A CLEVER STRUCTURE
Structurally, the new device is a sandwich of extremely thin layers of the semiconductor gallium arsenide alternated with similarly thin layers of light-emitting crystal, a sort of photonic fuel known as quantum dots. The structure is carved out of chips or wafers, much like sculptures are chiseled out of rock. Once sculpted, the devices remain tethered to the thick substrate.
Shambat and his fellow engineers have been working on similar optical devices for use in ultrafast, ultra-efficient computer applications where having devices immobilized on chips and wafers does not matter so much since they will ultimately be integrated with microelectronics.
For biological applications, however, the thick, heavy substrate presents a serious hurdle for interfacing with single-cells. The underlying and all-important nanocavities are locked in position on the rigid material and unable to penetrate cell walls.
Shambat's breakthrough came when he was able to peel away the photonic nanobeams, leaving the bulky wafer behind. He then glued the ultrathin photonic device to a fiber optic cable with which he steers the needle-like probe toward and into the cell.
Similarly, anticipating that gallium arsenide could be toxic to cells, Shambat also devised a clever way to encapsulate his devices in a thin, electrically insulating coating of alumina and zirconia. The coating serves two purposes: it both protects the cell from the potentially toxic gallium arsenide and protects the probe from degrading in the cell environment.
Once inserted in the cell, the probe emits light, which can be observed from outside. For engineers, it means that almost any current application or use of these powerful photonic devices can be translated into the previously off-limits environment of t
|Contact: Andrew Myers|
Stanford School of Engineering