Carbon Nanofibers (image) University of California - San Diego Caption Repeating bands of greater density give this bundle of carbon nanofiber photonic crystals a characteristic color. When the porous fibers absorb chemicals, they change color, making the material a sensitive optical sensor for chemical vapors. Credit Timothy Kelly, UCSD Chemistry and Biochemistry Usage Restrictions Permission granted for use to illustrate news reports on this new material. For other uses please contact firstname.lastname@example.org. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.