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Published online: 25 June 2008 | doi:10.1038/nchina.2008.146

Biomimetics: A sound strategy

Tim Reid

Introduction

© (2008) ACS

In nature, there are many materials with structures so sophisticated that the best replication approach is through casting processes. Shenmin Zhu, Di Zhang at Shanghai Jiao Tong University and co-workers¹ have made the casting process quicker and more accurate with the use of ultrasound.

The researchers picked biomaterials with unique one-, two- and three-dimensional structures — namely cotton, wood and butterfly wings — for replication. The materials were treated in acid and alkali baths, before being exposed to ultrasound in a solution of potassium permanganate. The samples were then calcinated (heated) to remove the biological templates, leaving a replica made from crystallized manganese oxide.

The researchers found that the replicas maintained the spiral twisted structures of cotton fibres, the hollow honeycomb-shaped pores in wood, and the tiny scales and ridges that provide the iridescent colours on butterfly wings (pictured). Most structures were accurate down to the nanometre level, although the replicas were generally smaller than the templates by around 20%.

The manganese oxide replicas are just as accurate as previous titanium oxide replicas of biological materials, but can be prepared far more quickly. The process could lead to new materials that combine biological functions with the useful magnetic, electronic and chemical properties of manganese oxide.

The authors of this work are from:
State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China; Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA; Faculty of Engineering, University of Wollongong, Wollongong, New South Wales, Australia.

Reference

1. Zhu, S., Zhang, D., Li, Z., Furukawa, H. & Chen, Z. Precision replication of hierarchical biological structures by metal oxides using a sonochemical method. Langmuir doi: 10.1021/la7037153 (2008).  | Article |