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4
Metals in Medicine, Volume 1
TABLE 1.1
12
Material
type
Material Pore size and
morphology
Biomedical applications
(i) Inorganic
Anodic aluminum
oxide (AAO)
pores, high density
Cell culture, biosensing: drug delivery,
molecular sieving, chromatography.
Si, SiO
2
, other
semiconductors
pores, high density
Biosensing, cell culture, drug delivery,
biomimicking.
(ii) Organic
(pore
morphology
defined by
fabrication
process)
Polydimethylsiloxane
(PDMS)
operation, organ on chip, bioassay.
Polycarbonate (PC) 1 nm–1 mm
PE >20 nm
Polystyrene (PS) 0.7 nm–1 pm
delivery.
Parylene 5 nm–1 mm Cell culture, drug delivery,
100 nm–8 µm
and organ chips.
Polymethyl
methacrylate (PMMA)
0.7 nm–5 µm Drug delivery.
Polylactic acid (PLA) 300 nm–1 µm Wound care, bone regeneration,
adhesive anchor.
(iii) Polymer
composite
Oxide + polymer
-
trochemical, liquid metal dealloying (LMD), vapor phase, and solid phase
dealloying.
21
NP-metal structures, and reduced reliance on extremely corrosive solvents.
22
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23
-
24
Source
https://t.me/med1917
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Metals in Medicine, Volume 1
TABLE 1.2
1
Fabrication technique Advantages Disadvantages
1. Dealloying Electrochemical
• Better control over porosity and chemical composi-
tion than chemical dealloying.
•
•
•
•
•
•
• -
chemical potentials.
Chemical
•
•
•
•
•
•
•
•
Vapor phase
•
•
•
and high-throughput production.
•
Liquid metal
•
• electrochemical dealloying and
•
• Faster due to operation at higher temperatures.
• Requires high temperatures.
• Unavoidable thermal coarsening.
•
solubility.
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Recent Advancements in Nanoporous Metal Foams for Biomedical Applications
7
TABLE 1.2 (Continued)
Fabrication technique Advantages Disadvantages
2. T emplating Soft
• Good control over geometry, •
•
•
• Simple technique.
•
• Not scalable approach.
•
Hard
• •
template. nanopores.
• Retaining hard geometries. •
• High cost and require multiple steps.
• Not scalable.
•
3. Microwave-based fabrication
• •
• •
MOF limiting the industrial scale production.
•
• Rapid process
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8
Metals in Medicine, Volume 1
( )
A
AN
x
dx
DD
dt x
∂
−
= −
∂
(1.1)
x is dealloying depth, t is dealloying time, x
A
active atoms, and D
A
and D
N
yields the dealloying rate.
( )
A NA
D DX
v
x
−
=
(1.2)
24
:
2
}{2( )
A NA
x D Dx= − (1.3)
by Pickering and Wagner in the latter 1960s. According to this theory, the
Source
https://t.me/med1917
Recent Advancements in Nanoporous Metal Foams for Biomedical Applications
9
-
25
:
b -
diss
B
exp
E
aE
Kv
kT
∅
= −
(1.4)
b
diff D
B
exp
aE
Kv
kT
= −
(1.5)
E
b
is the bond energy,
and silver and ϕ
(k
B
) and absolute temperature (T
13
s
4
s
25
1.2.1.1 CHEMICAL DEALLOYING
26
claim
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10
Metals in Medicine, Volume 1
1.2.1.2 ELECTROCHEMICAL DEALLOYING
Rahman et al.
27
30
Al
70
) may be
electrochemically dealloyed to create NP nickel. Compared to conventional
copper has been created by dealloying a copper-aluminum alloy.
1.2.1.3 LIQUID METAL DEALLOYING “LMD”
Rather than employing an acid environment, this approach uses liquid metal
-
dissimilar equilibrium potentials so that the more-noble (MN) element can
D
s
,
porous structures It is crucial that the surviving nobler atoms have enough
dealloying time. Equation 1.6 can be used to quantitatively determine D
s
the ligaments.
D
s
tkT 32𝛾tα
4
(1.6)
k
J.K.
), T is the dealloying
temperature, d(tt, and γ
https://t.me/med1917
Recent Advancements in Nanoporous Metal Foams for Biomedical Applications
11
–11
to 1010
–19
cm
2
s
28
)
y
Cu
alloys in liquid magnesium,
can be used in Mg and are both biocompatible and immiscible (see Fig. 1.3).
29
liquid metal C (e.g., Mg melt).
Source
2
-rich
microstructure.
30
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12
Metals in Medicine, Volume 1
-
-
Drug distribution could potentially be accomplished using the LMD-tailored
31
1.2.1.4 VAPOR PHASE DEALLOYING
1
Pinna et al.
32
20
Zn
80
1.2.1.5 SOLID PHASE DEALLOYING
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Recent Advancements in Nanoporous Metal Foams for Biomedical Applications
13
-
metal solvent substrate or both the precursor and the dealloying medium in
33
as the “template.” When these organic molecules are taken out, a cavity is
-
34
and alcohol, Stöber et al. (1968) produced silica nanoparticles employing
the sol–gel process.
( )
2 22
4
Si OEt +4H O SiO +2H O+4EtOH→
(1.7)
substances that generate pores are called porogens or structure-directing
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