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Biointerfacial Characterization www.rci.rutgers.edu/~moghe/583.html. BME 125:583. Lecture 1 Sep. 7, 2006 Prof. Prabhas Moghe. PROPERTIES OF MATERIALS. P. Moghe. • Bulk and Surface Properties Can Control Tissue Interface Dynamics After In Vivo Implantation of Biomaterials.
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Sep. 7, 2006
Prof. Prabhas Moghe
• Bulk and Surface Properties Can Control Tissue Interface
Dynamics After In Vivo Implantation of Biomaterials
• Bulk and Surface Material Characteristics are Property
Dependent - These Features must be known prior to any
e.g. does the application require load-bearing materials?
does the application require a soft, resorbable material?
- Interatomic forces
- Atomic structure based material classes-
Metals, Ceramics, Glasses, Polymers
-3-D atomic clusters
-Grain size and phase changes
-Mechanical Properties of Materials
• Surface properties determine biomaterial-tissue interface.
• Properties: Biocompatibility
-Molecules exterior to materials are most accessible to adjacent phases as well as incoming cells (Surface Reaction)
-There is always a positive energy necessary to create a unit area of surface. Systems reach equilibrium by minimizing this surface area/energy. In solids, this happens by changing the nature of interface to one with lower (lowest) energy.
-Energy minimization occurs when groups/chains in polymer rearrange to yield lowest interfacial energy.
e.g. hydrogel migrates to/from surface of a graft copolymer
exposed to water/dry air.
Determination of Surface Energetics
At equilibrium, surface energy
DuNouy Ring or
Wilhelmy Plate Method for
Contact Angle Measurement
where Fb = rL Vimm g
Cos q - Fb
F = mg + p
Both liquid surface tension & L/S/V contact angle can be computed
First do experiment with fully wetting plate and find gL. Then mount
biomaterial on the recording balance and find cosq.
Drop-Image Program: http://www.ramehart.com/goniometers/dropimagefinn.htm
Dynamic contact analysis is done by increasing or
decreasing the drop volume until the three-phase
boundary moves over the surface.
Difference between advancing and receding contact angle is
called contact angle hysteresis.
is obtained on
Critical surface tension, c
PTFE : 19 dyn/cm
PVC : 41 dyn.cm
Interfacial free energy of adhesion = Cell-solid interfacial free
energy - Cell-liquid interfacial free energy - Solid-liquid
interfacial free energy.
Fadh = cs - cl - sl
If Fadh < 0, adhesion and spreading are energetically favorable
and Substratum free energy (wettability)
s [erg. cm-2]
Biomaterial Critical Surface Tension
Biomaterials with good adhesion
Relative biological interaction
Critical Surface Tension (dynes/cm)
Baier, Adv. Chem. Ser. 145:1, 1975