Integrating nanoelectronic devices onto live plants and insects

Conventional electronic devices are composed of stiff and brittle silicon materials which tend to be mechanically incompatible with nonplanar or flexible substrates; yet the future of electronics will be flexible and transparent. There are basically two ways of achieving this: develop low-cost generic batch process using a state-of-the-art CMOS process to transform conventional silicon electronics into flexible and transparent electronics while retaining its high performance. Or develop new substrates and techniques such as inkjet-printing of graphene or other semiconductor inks on flexible substrates. Taking the approach of flexible electronics one step further, researchers in Korea now have integrated all-carbon based electronic devices to live plants and insects.

Technologies to interface electronic circuits, especially sensor networks that have capabilities of transferring information and power wirelessly, with living flora and fauna can monitor the conditions of the environment, including the detection of chemical weapons, pollution, and infections, etc. In addition, the attached devices can function consistently as sensors even after the in vivo activities of animals and plants have stopped. The Korean researchers developed an unconventional approach for the in situ synthesis of monolithically integrated electronic devices based on single-walled carbon nanotube (SWCNT) channels and graphitic electrodes. The highly flexible transistors were formed directly by the in situ synthesis using patterned metal catalyst films and subsequently could be transferred to both planar and nonplanar substrates, including papers, clothes, and fingernails.

Carbon nanotubes have high sensitivity to a large number of different gases and vapors which are important in areas as diverse as environmental monitoring, process monitoring in industry, agriculture, personal safety, medicine, or security screening. Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. One advantage that CNTs offer for gas sensors is their fast response time and the fact that they react with gases at lower temperatures, sometimes even as low as room temperature. On the basis of these capabilities, the research team demonstrated a sensor platform which can be interfaced with inherent life forms in nature for monitoring environmental conditions wirelessly. To demonstrate the sensor technology, experiments have been conducted with real-time gas sensor arrays on a leaf of a live plant and on the epidermis of a live insect for the detection of stimulants of sarin nerve agent. This all-carbon electronic device demonstrated superb mechanical flexibility and good adhesion to the nonplanar surfaces of biomaterials.

The researchers are confident that their device technology may also find uses in a variety of other applications such as artificial skin that inculdes sensors and displays for collecting information, threat detection (toxins or pollutants), or as a component of wearable displays. The team are already planning to develop artificial skin for eletronics with unconventional geometries. They point out that remaining technical challenges arise from requirements for commercial applications, such as the need for long-distance detection, which can be improved by circuit design and using different nanomaterials.

(http://www.nanowerk.com/spotlight/spotid=35418.php)