12 J. Bai et al.
surgical sutures or biodegradable membranes, bullet proof vests and structural
applications. Moreover, silk based scaffolds for bone formation offer options to
address the limitation of existing materials, such as collagen (which has poor me-
chanical properties), poly(lactiv-glucolic) acid (which induces inﬂammation), and
hydroxypatite (which is not completely biodegradable).
Biomembranes made of
spider silk ﬁlm can also be used for pumping or as valves in microﬂuidic channels.
Spider silk’s robust structure and modiﬁable surface chemistry make it an ideal
candidate as a chemical sensor or actuator. Recombinant spider silk proteins
in plants and goat milk have been successfully demonstrated
to increase the
commercialization potential of spider silk dramatically.
Dragline silk is a type of spider silk made up of two different but similar
proteins (ﬁbroins). In the secondary structure of these proteins, alanine-rich
regions organize into beta-sheets which form the core of crystalline structures
held together by hydrogen bonds. The glycine rich regions are less ordered.
It is this combination of crystalline and amorphous regions that is responsible
for the strength and extensibility of spider silk.
Regenerated spider silk is
ﬁrst harvested from spiders, dissolved into solvents and then re-spun through an
oriﬁce. Mechanical properties, such as the toughness of the regenerated silk, rely
largely on the assembly process of the proteins during re-spinning and drying.
However, the tensile strength of native silk is found to be three times higher than
that of regenerated spider silk.
Many microelectromechanical systems (MEMS) require a magnetic aspect to
be incorporated in the function; therefore, studies to incorporate magnetic prop-
erty components into MEMS structures have been undertaken.
For example, thin-
ﬁlm NiFe attached to a polysilicon micro cantilever beam was shown to actuate
under a magnetic ﬁeld
More recently, polydimethylsiloxane (PDMS) was mixed
with NdFeB particles to form a magnetic membrane used in a micro pump.
Several magnetic oxide nanoparticles, including Fe
and magnetite, have been
synthesized with particle sizes between 4–16 nm by using microemulsion, elec-
trochemical deposition, and other methods.
Composite ﬁlms consisting of
iron-iron oxide have also been achieved through chemical vapour deposition of
More importantly, polymer coated magnetic nanoparticles
have been fabricated using thermal deposition in the presence of ammonia and
However, most of these magnetic incorporation methods
require high temperature, high pressure or very expensive instrumentation to aid
in the fabrication.
This chapter will describe a new magnetic spider silk composite fabricated
using a regenerated spider silk matrix and iron pentacarbonyl (Fe(CO)
) at room
temperature and atmospheric pressure. Nanoparticles of iron oxides were made
via photolysis of iron pentacarbonyl using UV light instead of thermal or chemical
decomposition. Fourier Transformed Infrared Spectroscopy (FTIR) was used to
characterize the interaction of iron pentacarbonyl with spider silk proteins. A
micro cantilever beam made of iron oxide nanoparticles in thin-ﬁlm spider silk
was fabricated. The micro beam was actuated using magnetic ﬁeld.
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