Flashcards
Biomaterials Surface: Physics (wk. 3)
Flashcards do conjunto (26)
- 1Biomaterials Surface - Physics Key concepts1. bonding
2. surface tension/ adhesion & cohesion
3. hydrophobicity - 2ionic bond(metal + nonmetal)
High BP, high MP
solid - insulator e-
molten/aqueous - conductor e-
HARD, BRITTLE - 3Covalent bonding(nonmetal + nonmetal)
s, l, g at room Temp
s, l, g, poor conductor
low MP, low BP
Soft, brittle, cleaves
non electrolyte - 4Metallic bondingdelocalized electrons/bonds
good e- and thermal conductor
opaque
relatively ductile
contain 1 to 3 electrons outer shell - 5Van der Waals Bondweak attractive/repulsive force betw molecules
partial dipoles
occur to some extent in all materials, important for polymers - 6Polymers - important bondscovalent + van der waals
covalent: STRONG - carbon back bone, strong, rupture only in extreme conditions. key for thermosetting
van der waals: WEAK allow sliding, rupture. Key for thermoplastics
thermoplastics: head breaks van deer Waal forces
thermosetting: 3D network of covalent bonds, don't break easily - 7Amorphous Solidrandom
supercooled liquids
nio long range periodicity
e.g., glass (SiO2 cooled rapidly to prevent crystallization - 8Crystalline solids>90% of solids ares crystalline
more stable, minimized intermolecular energy
regular arrangements - 9Surface properties influencing protein and cell adhesion (3)surface hydrophobicity (proteins like)
surface roughness (cells like)
surface charge (determined by peptide sequence) - 10Cohesive forceattraction betw SAME molecules
- 11Adhesive forceattraction betw DIFFERENT molecules
adhesive tape: sticks two different things together. - 12Surface tension (T or gamma)tendency of molecules on the surface of a liquid to go into the liquid
- 13Surface tension formula
- 14Capillary actionadhesion to walls > cohesion liquid
upward force raising liquid forms miniscus
T holds surface intact
height dependent on T - 15Capillary action: Force Upward formula
- 16high surface tension (T) materialsmetals
carbides
oxides
(strong bonds, metallic & covalent bonds) - 17low surface tension (T) materialspolymers, organics
(van der waals bonded) - 18Work of CohesionSurface tension is a measure of degree of cohesion
- 19Work of AdhesionWork required to separate a unit area of interface between to phases
- 20Protein resistance by work of adhesionW12 = 0
higher work adhesion of water, water will be harder to displace by protein, protein resistance is good - 21—
- 22—(a) >90 = non wetting = hydrophobic
(b) <90, partial = hydrophillic
>150 is superhydrophobic/ ultraphobic
- 23Cassie's equation
- 24Wenzel equation
- 25—use wenzel's equation
cos(pheta)* = rcos(pheta)
pheta*= arccos(rcos(pheta))
- 26—
