Spider Silk as a MEMS Material 27
Magnetic Induction (kOe)
Vertical displacement (mm)
Figure 2.16. Bending distance as magnetic induction (ﬁeld) increases.
spectra of regenerated spider silk in a thin-ﬁlm form have been measured
to the suggestion that the β-sheet conformation, which is responsible for the high
stiffness and strength of spider silk,
is missing from thin-ﬁlm spider silk. This
result indicates a dramatic change in the material’s secondary structure compared
to its native ﬁber state. Furthermore, the signiﬁcant decrease in mechanical
property shown in Ni/spider-silk ﬁlm silk is perhaps due to the porosity of the
material, which would allow stress concentration to occur around the Ni particles.
The material property could be improved if the dilution of Ni/spider silk was
reduced. However, in this work the near maximum dilution was used in order
increase the material’s magnetic properties.
Furthermore, contact with water during the release step also affects the
strength of the microbridge. Previous studies have shown that water causes
changes in the arrangement of the silk ﬁbroins and causes super-contraction of
the silk ﬁbers, which can decrease the UTS and increase the brittleness of the
When regenerated ﬁbers were stretched in water, the UTS was
reduced to 25 MPa.
It is unlikely that our silk structures would super-contract
as native ﬁbers do; however, the immersion in water likely does enable some
rearrangement of the protein-polymer backbone. The regenerated Ni/spider silk
studied in this work has a comparable UTS to PDMS (with UTS in the range of
2.4–7 MPa [mit]), a popular material in MEMS.
2.4 CONCLUSIONS AND OUTLOOK
This chapter has presented regenerated Ni/spider silk as a material for MEMS.
Thin-ﬁlm formation using a spin-on process and a modiﬁed surface microma-
chined Ni/spider-silk microbridge were demonstrated. Static and dynamic bend-
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