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Instead, Velev and his collaborators took a different approach, reinforcing the agarose films with fibrillated colloidal scale material -- called soft dendritic colloids -- made from chitosan.

The strong chitosan micro- and nanoscale fibrils are hierarchically branched to provide strength and stability to the agarose film where they are embedded.

"We use chitosan dendritic particles to reinforce the agarose matrix because of the compatibility of both materials leading to good mechanical properties; chitosan particles also have an opposite charge to agarose. When mixed, these charges are neutralized so the resulting materials also become more resistant to water."

The biopolymer composites are about four times stronger than agarose films alone, the research shows, and also resist E.coli, a commonly studied bacterium.

Combining chitosan, a biopolymer that makes crab shells hard, with agarose, a biopolymer extracted from seaweed that is used to make gels, creates unique biopolymer composite films with enhanced strength.