The Photonics Research Institute (PRI) of the National Institute of Advanced Industrial Science and Technology (AIST), an independent administrative institution, has succeeded in developing, first in the world, a bio-photosensor (biological photo-electronic converter device) to transform light to electricity by combining bio-conjugated materials with semiconductor devices, in collaboration with a study group consisting of scientists from Science University of Tokyo, University of Tokyo, Shizuoka University, and Tokyo Institute of Technology.
This R&D work has been carried out under the Ministry of Education and Science (MEXT) Program, “Creation of Bio-Conjugate Photosensor Nano-Materials”, FY2002~2004, leader: PRI- AIST.
An array of photosensors, i.e. photo-electronic transducers, is called an imaging device. Currently, the main stream of imaging device is filled by semiconductor devices, represented by charge-coupled devices (CCD). The miniaturization of CCD results in a photo acceptance element, as small as 1μm square (1μm=1/1,000,000m). Such a highly integrated device involves certain troubles such as heat dissipation and thermal noises preventing sensitivity from being raised. As a breakthrough solution for this situation, the PRI succeeded in developing a key technology for biological photo-electronic transducer based on the application of bio-conjugated materials in an imaging device.
In this device, photoreceptor protein extracted from cyanobacteria living in a hot spring is combined with conductive molecular wire prepared through organic synthesis and impregnated with gold nano-particles. With an imaging device consisting of assemblies with bio-conjugated materials integrated on semiconductor devices (FET), the operation of bio-electronic transducer was confirmed.
The work will be extended in future to the development of a bio-electronic imaging device with higher degree of integration, leading to the establishment of bio-electronic industrial technology and innovative materials science.
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Fig. 1
A schematic drawing of bio-photosensor. A photoreceptor illuminated by light emits electrons, which are led through integrated molecular wirings to gold flow gate of FET and given out as electrical signals. |
It is no exaggeration to say that the semiconductor industry is ever seeking for ultra-fast processing and ultra-high packing density, but technological limitations occur one after another. It is claimed that nano-technology is a key technology for solving these troubles and leading the industry of next generation. There is another move to implement innovative devices of ultra-high speed and ultra-high packing density through entirely new technology based on synthetic approach involving molecular and supramolecular components.
While technologies handling biological materials and molecular devices are still in a rudimentary stage, it is expected that they will enable new type of devices characterized by ultra-high packing density and energy saving, which could not be achieved with the semiconductor technology.