“They will be able to detect physical parameters such as biological and chemical substances, displacement and motion, force and mass-acoustic, thermal, and electromagnetic stimuli,” says Daniela Carrillo, a research analyst in the sensors group at Frost & Sullivan Inc. (San Antonio).

According to Carrillo, there are three types of nanosensors: nanostructured particles, nanoparticles and nanodevices.

Nanosensors that are made out of nanostructured particles are typically microdevices, but the material used to build them has nanoscale features. For instance, porous silicon is one type of nanostructure material. Some examples of sensors that have been created using nanostructured porous silicon include optical biosensors, DNA detection sensors, ethanol detection sensors and photodetectors. Carrillo says initial applications for nanostructured materials are personal and healthcare products, catalysts, electronics, chemical mechanical polishing, thermal sprays, and a variety of coatings for abrasion resistance, and ultraviolet-infrared attenuation.

Nanoparticle sensors can be used either within the body or outside the body for disease detection, cellular repair and drug delivery. Nanoparticles have been made in three size ranges: micro (more than 10 nanometers), meso (10 to 100 nanometers) and macro (more than 100 nanometers). Most nanosensors have been fabricated in the meso and macro size ranges. Carrillo says these are primarily used as biochemical sensors. Nanoparticle sensors can measure pH, calcium, sodium, potassium, chloride, oxygen, glucose, glutamate and magnesium. They also can detect biological warfare agents, such as anthrax. Nanoparticles have also been developed as opto-bioreceptor, opto-chemical and spatial imaging sensors.

Nanodevices include resonant cantilever systems that absorb mass and vary their resonant frequency depending on how much of a biological or chemical substance is detected. These devices are projected to act as sensors that detect tumors and then release drugs to attack the tumors by actively bending to open a gate to release the drug. “Most of the nanodevices needed to create nanosensors exist only in theory, or the pieces of the system exist, but not an integrated device,” notes Carrillo. “Biomedical applications are the driving force for the development of nanosensor technologies, with a particular focus on in vivo and intracellular nanosensors.

“One of the biggest challenges for nanosensors is the ability to interface between nanoscale devices, microsystems, and macrosystems,” adds Carrillo. “Nanosensors will need to convert optical, chemical, biological and electrical data into signals that can be transmitted within nanosensor systems, and that can be acquired by data acquisition systems and computers that allow for human interaction and analysis.”

According to Carrillo, future nanosensor devices will need to build upon technology that is currently under development such as nanoelectro mechanical systems (NEMS), single electron transistors (SET), biomolecular motors, molecular switches, nanotubes and nanowires. “Each of these technologies will play a key role in the development of true nanosensor devices that don’t require macro scale detection equipment,” claims Carrillo.

“Nanotechnology will continue to evolve as both the government and investors work together with companies to allow them to design reliable, innovative and cost-effective nanosensors,” Carrillo predicts. “In fact, the U.S. government has increased its annual budget for nanotechnology research to $650 million for 2003.”