Carbon Nanotube Chemiresistors

A new generation of electrochemical sensors known as chemiresistors is serving as a platform for the detection of a broad range of contaminants in our air, water, and food. The companies deploying these platforms are leveraging a broad range of technologies to make their systems more versatile and more scalable.

The core component of any of these systems is, of course, the sensor itself. This is where the challenges begin. For example, a single sensor for a single analyte, or a multi-sensing approach? Single-use, multi-use or perpetual? How to balance these approaches against the cost of deployment and maintenance?

A number of researchers and commercial developers have chosen to take advantage of the robust nature and conductivity of single-walled carbon nanotubes as a "base material" in their sensor designs. In these designs, the CNTs are either coated with different materials or functionalized directly to predispose them to react with different analytes. In the presence of the designated analyte the resistance of the CNT network changes, those changes correlated to baseline data, etc.

While some companies have chosen to incorporate CNTs and other sensing technologies into chip architectures, others are making the sensor a "disposable." In those cases manufacturability becomes a concern as the sensors themselves become a consumable commodity.

Representative Solution

A client was developing a chemical sensor to detect the presence of a particular noxious chemical in the air. They had made the decision to use CHASM's SG65i semiconducting CNTs, but had a number of key challenges:

• CNTs had to be applied to a flexible substrate with NO surfactant

• CNT film morphology had to consistent

• CNT film needed to have predictable resistance

• Final sensor has to be produced cost-effectively in high volumes

The ultimate solution leveraged CHASM's V2V ink technology, into which the SG65i was dispersed with zero surfactants, in a targeted concentration.

The result:

• A viscous, screen printable semi-conducting CNT ink

• A sensor that could be produced cost-effectively in volume

• A scalable, reliable sensor design