Determinations of the viscoelastic properties of extracellular matrices (ECMs) are becoming increasingly important for accurate predictive modeling of biological systems. Since the interactions of the cells with the ECM and surrounding fluid (e.g., blood, media) each affect cell behavior; it is advantageous to evaluate the ECM’s material properties in the presence of the hydrating fluid. Conventional rheometry methods evaluate the bulk material properties of gel materials while displacing the hydrating liquid film. Such systems are therefore nonideal for testing materials such as ECMs, whose properties change with dehydration. The new, patent pending, piezoelectrically actuated linear rheometer is designed to eliminate this problem. It uses a single cantilever to apply an oscillating load to the gel and to sense the gel’s deflection. Composed of two thin film piezopolymer layers, the cantilever uses one layer as the actuator, and the second piezopolymer layer to measure the lateral movement of its attached probe. The viscoelastic nature of the ECM adds stiffness and damping to the system, resulting in the attenuation and phase shift of the sensor’s output voltage. From these parameters, the ECM’s shear storage and loss moduli are then determined. Initial tests on the BioMatrix I and type I collagen ECMs reveal that the first prototype of the piezoelectrically actuated linear rheometer is capable of accurately determining the trend and order of magnitude of an ECM’s viscoelastic properties. In this paper, details of the rheometer’s design and operating principles are described.

1.
Barocas
,
V.
,
Moon
,
A.
, and
Tranquillo
,
R.
,
1995
, “
The Fibroblast-Populated Collagen Microsphere Assay of Cell Traction Force—Part 2: Measurement of the Cell traction Parameter
,”
ASME J. Biomech. Eng.
,
117
, pp.
161
170
.
2.
Coger
,
R.
,
Moghe
,
P.
,
Ezzell
,
R.
,
Yarmush
,
M.
, and
Toner
,
M.
,
1997
, “
Hepatocyte aggregtion and the reorganization of EHS matrix gel
,”
Tissue Eng.
,
3
, pp.
375
390
.
3.
Yannas
,
I.
,
Burke
,
J.
,
Orgill
,
D.
, and
Skrabut
,
E.
,
1982
, “
Wound Tissue Can Utilize a Polymeric Template to Synthesize a Functional Extension of Skin
,”
Science
,
215
, pp.
174
174
.
4.
Snyder, J., 1999, “A New Instrument for Evaluating the Stresses Hepatocytes Produce During Aggregation,” Masters thesis, University of North Carolina at Charlotte, Charlotte, NC.
5.
Bissell
,
M.
,
Hall
,
H.
, and
Parry
,
G.
,
1982
, “
How does the extracelluar matrix direct gene expression?
,”
J. Theor. Biol.
,
99
, pp.
31
68
.
6.
Neville
,
M.
,
Stahl
,
L.
,
Brozo
,
L.
, and
Lowe-Lieber
,
J.
,
1991
, “
Morphogenesis and Secretory Activity of Mouse Mammary Cultures on EHS Biomatrix
,”
Protoplasma
,
163
, pp.
1
8
.
7.
Fung, Y., 1993, Biomechanics Mechanical Properties of Living Tissues, Springer, New York.
8.
Hsu
,
S.
,
Jamieson
,
A.
, and
Blackwell
,
J.
,
1994
, “
Viscoelastic Studies of Extracelluar Matrix Interactions in a Model Native Collagen Gel System
,”
Biorheology
,
31
, pp.
21
36
.
9.
Barnes, H., Hutton, J., and Walters, K., 1989, An Introduction to Rheology, Elsevier Science, Amsterdam, The Netherlands.
10.
Thurston
,
G.
,
1994
, “
Non-Newtonian Viscosity of Human Blood: Flow Induced Changes in Microstructure
,”
Biorheology
,
31
, pp.
179
192
.
11.
Zhu
,
W.
,
Chern
,
K.
, and
Mow
,
V.
,
1994
, “
Anisotropic Viscoelastic Shear Properties of Bovine Meniscus
,”
Clin. Orthop. Relat. Res.
,
306
, pp.
34
45
.
12.
Iatridis
,
J.
,
Setton
,
L.
,
Wedienbaum
,
M.
, and
Mow
,
V. C.
,
1997
, “
The Viscoelastic Behavior of the Non-Degenerate Human Lumbar Nucleus Pulposus in Shear
,”
J. Biomech.
,
30
, pp.
1005
1003
.
13.
Jameson
,
M.
,
Hood
,
J.
, and
Tidmarsh
,
B.
,
1993
, “
The Effects of Dehydration and Rehydration on Some Mechanical Properties of Human Dentine
,”
J. Biomech.
,
26
, pp.
1055
1065
.
14.
Haut
,
T.
, and
Haut
,
R.
,
1997
, “
The State of Tissue Hydration Determines Strain-Rate-Sensitive Stiffness of Human Patellar Tendon
,”
J. Biomech.
,
30
, pp.
79
81
.
15.
Sasaki
,
N.
, and
Enyo
,
A.
,
1995
, “
Viscoelastic Properties of Bone as a Function of Water Content
,”
J. Biomech.
,
28
, pp.
809
815
.
16.
Stading
,
M.
, and
Langer
,
R.
,
1999
, “
Mechanical Shear Properties of Cell-Polymer Cartilage Constructs
,”
Tissue Eng.
,
5
, pp.
241
250
.
17.
Ziemann
,
F.
,
Radler
,
J.
, and
Sackmann
,
E.
,
1994
, “
Local Measurements of Viscoelastic Moduli of Entangled Actin Networks Using an Oscillating Magnetic Bead Micro-Rheometer
,”
Biophys. J.
,
66
, pp.
2210
2216
.
18.
Radmacher
,
M.
,
Tillmann
,
R.
, and
Gaub
,
H.
,
1993
, “
Imaging Viscoelasticity by Force Modulation with the Atomic Force Microscope
,”
Biophys. J.
,
64
, pp.
735
742
.
19.
Hopfer
,
H.
,
Rinhart
,
C.
,
Vollmer
,
G.
, and
Kaufman
,
D.
,
1994
, “
In vitro Interactions of Endometrial Stromal and Epithelial Cells in Matrigel: Reorganization of the Extracelluar Matrix
,”
Pathobiology
,
62
, pp.
104
108
.
20.
Halvorsen
,
D.
,
1994
, “
Putting Piezo Polymer Film to Work
,”
Mach. Des.
,
66
, pp.
47
51
.
21.
Sessler
,
G. M.
,
1981
, “
Piezoelectricity in Polyvinylidenefluoride
,”
J. Acoust. Soc. Am.
,
70
, pp.
1596
1608
.
22.
Ikeda, T., 1990, Fundamentals of Piezoelectricity, Oxford University Press, NY.
23.
Rao, S., 1995, Mechanical Vibrations 3rd Ed., Addison-Wesley, Reading, MA.
24.
Tzou
,
H.
, and
Ye
,
R.
,
1996
, “
Pyroelectric and Thermal Strain Effects of Piezoelectric (PVDF and PZT) Devices
,”
Mech. Syst. Signal Process.
,
10
, pp.
459
469
.
25.
Young, H., 1992, University Physics—8th Ed., Addison-Wesley, Reading, MA.
26.
Woo
,
S. L.-Y.
,
Gomez
,
M. A.
, and
Akeson
,
W. H.
,
1981
, “
The Time and History-Dependent Viscoelastic Properties of the Canine Medial Collateral Ligament
,”
ASME J. Biomech. Eng.
,
103
, pp.
293
298
.
27.
Christensen, R., 1982, Theory of Viscoelasticity—2nd Ed., Academic Press, New York, NY.
28.
Smith, R., and Dorf, R., 1992, Circuits, Devices, and Systems 5th Ed., Wiley, New York, NY.
29.
Lide, D., 1997, CRC Handbook of Chemistry and Physics—78th Ed, CRC Press, New York, NY.
30.
Elmore
,
S.
,
Sopkoloff
,
L.
,
Norris
,
G.
, and
Carmeci
,
P.
,
1963
, “
Nature of ‘Imperfect’ Elasticity of Articular Cartilage
,”
Journal of Applied Physiology
,
18
, pp.
393
396
.
31.
Knapp
,
D.
,
Barocas
,
V.
,
Moon
,
A.
,
Yoo
,
K.
,
Petzold
,
L.
, and
Tranquillo
,
R.
,
1997
, “
Rheology of Reconstituted Type I Collagen Gel in Confined Compression
,”
J. Rheol.
,
41
, pp.
971
993
.
32.
Carbeck
,
J.
, and
Rutledge
,
G.
,
1996
, “
Temperature Dependent Elastic, Piezoelectric and Pyroelectric Properties of b-poly(vinylidene fluoride) from Molecular Simulation
,”
Polymer
,
37
, pp.
5089
5097
.
You do not currently have access to this content.