Chapter 7 – Complementary Experimental Tools  287

involved in their formation (see Chapter 9). The chitin fibrils form periodic ridge structures,

with the spacing between ridges being typically a few hundred nanometers, dependent on the

butterfly species, resulting in photonic bandgaps, and the colorful, metallike appearance of

many butterfly wings that remains constant whatever the relative angle of incident light and

observation direction.

Synthetic photonic crystals come under the description of advanced materials or

metamaterials. Metamaterials are those that are not found in nature; however, many of

these have gained inspiration from existing biological structures, and in fact several can be

described as biomimetic (see Chapter 9). Artificial photonic crystals utilize multilayered thin

metallic films using microfabrication techniques (see the following section in this chapter),

described as thin-​film optics, and such technologies extend to generating photonic crystal

fibers. For example, these have biophysical applications for lab-​on-​a-​chip devices for propa­

gating specific wavelengths of excitation light from a broadband white-​light source, while

another photonic crystal fiber propagates fluorescence emissions from a fluorescently labeled

biological sample for detection that disallow propagation of the original excitation wave­

length of light used, thus acting as a wavelength filter in a similar way to conventional fluor­

escence microscopy, but without the need for any additional large length scale traditional

dichroic mirror or emission filter.

Structured light is used as the general term for light whose properties have been control­

lably engineered, many examples involving the application of photonic features, and since

there are multiple examples of this in nature, it has led to several examples of bio-​inspired

technologies, so-​called biomicry, utilizing structured light (see Chapter 9).

7.6  HIGH-​THROUGHPUT TECHNIQUES

Coupled to many of these, more advanced biophysical characterization tools are a new wave

of high-​throughput techniques. These are technologies that facilitate the rapid acquisition

and quantification of data and are often used in conjunction with several core biophysical

methods, but we describe here in a devoted section due to their importance in modern

biophysics research. These include the use of microfluidics, smart microscope stage designs

and robotized sample control, the increasing prevalence of “omics” methods, and the

development of smart fabrication methods including microfabrication, nanofabrication,

and 3D printing technologies leading to promising new methods of bioelectronics and

nanophotonics.

7.6.1  SMART FABRICATION TECHNIQUES

Microfabrication covers a range of techniques that enable micron scale solid-​state structures

to be controllably manufactured, with nanofabrication being the shorter length scale pre­

cise end of these methods that permit details down to a few nanometer precision to be

fabricated. They incorporate essentially the technology used in manufacturing integrated

circuits and in devices that interface electronics and small mechanical components, or

microelectromechanical systems (MEMS). The methods comprise photolithography (also

known as optical lithography), chemical and focused ion beam (FIB) etching (also known as

electron beam lithography), substrate doping, thin-​layer deposition, and substrate polishing,

but also incorporate less common methods of substrate etching including x-​ray lithography,

plasma etching, ion beam etching, and vapor etching.

The state-​of-​the-​art microfabrication is typified with the publishing of the world’s smallest

book in 2007 entitled Teeny Ted from Turnip Town, which is made using several of these

techniques from a single polished wafer of silicon generating 30 micro pages of size 70 × 100

μm, with the FIB generating letters with a line width of just ~40 nm. The book even has its

own International Standard Book Number reference of ISBN-​978-​1-​894897-​17-​4. However,

it requires a suitably nanoscale precise imaging technology such as a scanning electron

microscope to read this book (see Chapter 5).

KEY BIOLOGICAL

APPLICATIONS:

CRYSTAL MAKING

Molecular structure deter­

mination through x-​ray

crystallography.