What exactly is a smart material?

Dr. Darlene Taylor is assistant professor of chemistry at North Carolina Central University.
Dr. Darlene Taylor is assistant professor of chemistry at North Carolina Central University.

Dr. Darlene Taylor is assistant professor of chemistry at North Carolina Central University. She explains how she and other like-minded scientists are infusing materials with intelligence. Questions and answers have been edited.

Q: How can a material be smart?

A smart material is one that responds to a change in its environment. Some changes that scientists manipulate include temperature, pressure, pH, electric field or magnetic field. The material is designed to respond to these changes by breaking bonds, changing colors, or becoming more rigid, to name a few examples.

Q: What are some materials we never knew were smart?

Absorbable sutures, drug-release systems and tissue reconstruction scaffolds are all examples of applications that involve smart materials. For example, stents that degrade over time eliminate the need for post-surgical removal.

Eyeglasses that turn to sunglasses in reaction to sunlight are based on photochromic materials that can change color upon exposure to ultraviolet illumination. Prototype smart sunglasses also are being developed in laboratories by coating the lens with a smart polymer, allowing the color to change when a switch powered by a watch battery sends an electrical current through the smart material.

Smart garments can include electroluminescence where the clothing can actually light up, and a smart second-skin that can cool you when you are hot and keep you warm when you are cold.

Clothes also can be made to become rigid or loose on command, allowing the wearer to cool down or heat up. The company REI sells some of these latter temperature-controlling fabrics now.

Q: How are smart materials made?

I mainly deal with polymeric smart materials, which are prepared by linking together several identical units called monomers, to create a long polymer chain. The design of many smart materials can be inspired by nature where the goal here is to determine an amino acid (building blocks of proteins) repeat pattern, associate that pattern with a function (like hardness or strength, or temperature response) and then replicate that with synthetic repeat patterns of amino acids to produce smart materials.

Q: What are some applications of smart materials your lab is exploring?

We are developing a number of copolymers that respond to changes in temperature (they gel), water (they degrade), and reduction-oxidation potentials (they can incorporate fluorescent tags or imaging agents).

Our goal is to better understand the structure-property relationship in these materials. Some of the applications we are exploring are improved delivery of drugs to treat uterine fibroids and the creation of solar cells that mimic the photosynthetic properties of plants.