Researchers explore electroactive medical bioplastics

The U.S. Agriculture Department is funding a five-year project to develop electroactive polymers from natural, renewable feedstocks such as cornstarch.

The implications are significant because commercially available electroactive polymers made from fossil fuels,

such as polyanaline, cost much more than corn starch (about 40 cents per pound in 50-pound bags).  Polyaniline emeraldine-based polymers can cost thousands of dollars per pound.

A research team at the Plant Polymer Research Unit of the National Center for Agricultural Utilization Research operated by the federal Agricultural Research Service demonstrated the technical feasibility of making electroactive polymers from starch in a technical paper published in 2005.

"Thermoplastic starch is naturally insulative; however, the chemical, electrical, and mechanical properties of the biopolymer matrix can be tailored for specific functionality in a continuous process utilizing reactive extrusion," the researchers wrote at the time. 

"Ion-conducting materials, produced by doping thermoplastic starch and biopolymers with metal halides, have five orders of magnitude greater conductance than native materials...The conductance approaches the level of synthetic polymer electrolytes."

In the reactive extrusion process, the starch is gelatinized with heat and moisture, plasticized with water, and doped-all in one continuous process.

Biocompatible insulin pumps

Importantly the bioplastics under study are biocompatible. That could lead to various medical applications, including controlled-release devices such as insulin pumps and nicotine patches.

"We are currently focused on electroactive applications (not necessarily conductive) such as anti-corrosion systems or membrane technology," says  Victoria Finkenstadt, lead scientist at the Plant Polymer Research Unit in Peoria, IL. "The biobased materials function by ion conductivity mechanisms rather than electronic in the case of synthetic conductive polymers (i.e. conjugated double bonds). We use commercially available products like proteins, carbohydrates and oils to produce different systems depending on the use or end-product. "

The government has funded a new five-year investigation into the electroactviity of starches and other renewable feedstocks. The current project expires in 2015. Goals of the study include development of new markets for U.S. agriculture products and to reduce dependence on foreign oil.