Biomedical Engineering Reference
In-Depth Information
Fig. 6.4.
Horizontal uniaxial mechanical testing device mounted on the stage of the multi-photon
microscope
tor and driver from Applied Motion Products (Watsonville, CA, USA) connected
to a Velmex (Bloomfield, NY, USA) linear slide is used to apply extension, and a
MDB-5 5-lb. capacity load cell (Transducer Techniques, Temecula, CA, USA) is
used to measure force. A custom clamping system is used to remove the specimen
under applied strain. An acrylic bath is constructed with a low profile, so the sub-
merged tissue is accessible by the MPM lens for imaging during mechanical testing.
The MPM is an an Olympus FV1000 MPE (Olympus, Tokyo, Japan) equipped with
a Spectra-Physics DeepSee Mai Tai Ti-Sapphire laser (Newport, Mountain View,
CA, USA) and a 1.12NA 25x MPE lens.
Tissue assessment using the UA-MPM system
In this illustrative example, we describe the application of the UA-MPM system
to evaluate circumferential samples of the left common carotid arteries from New
Zealand white rabbits and then use this data in a structurally motivated model for the
wall. Here, the arterial wall is modelled as a single layer multi-mechanism material
with isotropic and anisotropic mechanisms. Attention is focused on fibres contribu-
tions from the medial layer. The isotropic mechanism is modelled as a Neo-Hookean
material and the anisotropic mechanism is modelled using a generalized structure
tensor approach with conical splay, Eq. (6.23). Earlier studies suggest collagen re-
cruitment can be approximated as commencing at at a finite stretch and taking place
over a narrow stretch range [50]. Therefore, in this work, we approximate the col-
lagen recruitment stretch
λ
a
as a discrete, finite value. In particular, using (6.23)
and (6.36)
W
=
W
iso
+
W
aniso
,
with
W
iso
=
η
iso
(
I
0
−
3
)
,
e
γ
(
λ
1
)
η
γ
2
t
−
1
)
W
aniso
= H(
λ
t
−
1
−
