Can we get a banana to talk to us?

Food is perishable. From the point of view of consumers’ interests, that means we need up-to-date information on when it will spoil, as well as when it is fresh, and, in the event that it may be contaminated, where it was grown, when it was picked, and what is the contaminant. Growers, distributors, and retailers dream of precisely tracking food from the field to the store, optimizing processes, prices, and packaging. Current approaches to identifying food—stickers, radio frequency (RF) tags, and barcodes—are costly and largely lack sensing capabilities. They tell us what we’re holding in our hands but not what condition it is in—or will be in three days.

Bringing together the disciplines of mechanical engineering, computer science, and chemistry, this project will explore the possibility of creating a “smart” sticker with a chemically sensitive RF antenna that changes its response based on surrounding conditions such as temperature, or gas exposure, which is often a signature of food spoilage. “Many fruits release ethylene as a sign of ripeness,” says Dr. Hart. “The electrically responsive sensor in the sticker can detect the ethylene and report this information over a wireless network. Rather than a passive tag that holds a limited amount of pre-determined information, our sticker would proactively transmit information about the product’s health, and allow predictions to be made in the cloud.”

Creating a solution that is both effective and cost-effective

The challenges of building these printable nano-sensors are so great they require the combined skills and discoveries of three very different labs. Design of the RF-based solution is being performed by Dr. Katabi’s lab; creating the chemically sensitive carbon nanotubes is being done in Dr. Swager’s lab; and Dr. Hart’s lab is contributing the printing techniques they’ve invented. Each of these three areas of responsibility is a challenge unto itself, but it doesn’t end there. “The grand challenge is making this process so cost-effective that the cost of making a sensor and putting it on lettuce or other product would be essentially zero,” says Dr. Hart. “This has to scale to billions of products so the cost factor has to be a penny or less for each sticker.”

Better living through intelligent sensors

Grocery product recalls appear in the news frequently. These typically come about only after a critical mass of people have already gotten sick. Dynamic RF stickers that are chemically sensitive and have the ability to push out data can identify contaminants before they reach the public. In addition to protecting and better serving consumers, this data can also lead to better supply chain management, more intelligent inventory and storage practices, and less food waste. This same technology could also lead to wearable sensors for health and performance monitoring, responsive wound dressings, and smart packaging for sensitive medicines. According to Dr. Hart, “This project will push my comfort zone into a bold new direction, and begin a very exciting collaboration.”

Multidisciplinary research bears fruit

“Our research has shown steady progress,” says Dr. Hart. “While we aren’t yet at the point where food stickers can be widely manufactured and put to use, we continue to develop and refine sensors that combine carbon nanotubes (CNTs) from Dr. Swager’s group that react to gasses, along with antennas that allow data to be measured over a simple radio frequency (RF) protocol.” Assisting in the progress is a graduate student, Alexander “Olek” Peraire-Bueno, who knows manufacturing and RF design, and has been developing routines for optimizing the antenna so that it can be manufactured cost-effectively.

“We spent a lot of time learning how to print the material, and how to organize the CNTs to maximize the electronic properties that would make the system work. It is truly a cross-disciplinary project. Olek was a great find for us,” says Dr. Hart. Next steps for the group include the following:

• Pulling together a second paper showing integration of the new antenna design with CNT sensors
• Continuing to innovate on chemistries and how they can be sensed
• Exploring numerical ways to optimize the design and 3D printing of the antennas
• Discussing with the rest of the team their goals in terms of market application