Photonic nanoarchitectures occurring in butterfly scales as selective gas/vapor sensors

Abstract

ABSTRACT Photonic band gap material type nanoarchitectures occurring in the wing scales of butterflies possessing structural color were investigated as selective gas/vapor sensors. From 20 examined butterfly species all showed selective sensing when various volatile organic compounds were introduced as additives in ambient air. Four butterflies species: Chrysiridia ripheus (Geometridae), Pseudolycena marsyas , Cyanophrys remus (both Lycaenidae) and Morpho aega (Nymphalidae) were selected to demonstrate the possibilities of selective sensing offered by these natural nanoarchitectures. Each butterfly species gives characteristic response both for species, i.e., for its typical nanoarchitecture, and for the seven test vapors used. Fast response time, reproducible and concentration dependent signals are demonstrated. Keywords: butterfly wing scales, nanoarchitecture, photonic crystal, photonic band gap (PBG), selective gas/vapor sensor, volatile organic compounds (VOCs), optical reading, bioinspiration. 1. INTRODUCTION Beyond their charming beauty butterflies may reveal a number of “design principles” which were carefully distilled to perfection during many millennia of natural evolution. This is particularly true for those colors which have role in sexual communication or cryptic behavior. Individuals with the “wrong color” have lesser chances to find a mating partner, or are predated early, before they could have the ch ance to reproduce. In the pres ent paper we are interested in those natural designs which concern photonic nanoarchitectures occurring in the wings of butterflies. These nanoarchitectures are named photonic crystals (PhC), or photonic band gap (PBG) materials by physicists and materials scientists. The concept of these composite materials built of two materials with distinct optical properties (refractive index) was introduced 20 years ago by Yablonovitch [1] and John [2]. The wings of butterflies are covered by scales, which are the cu ticular product of a single cell. Typical scale dimensions are in the 100 x 50 x 1 P m