Fajun Zhang 109.12.2011
Biofouling and Anti-Biofouling Interface
OutlineBiofouling/Protein adsorptionProcedure of biofoulingSurface energy, adhesionStrategy of anti-biofouling
Fajun Zhang
Fajun Zhang 209.12.2011
Biofouling
Biofouling is non-desirable accumulation and growth of living matter (micro-organisms) on material surface;World wide problem with
Pulp and paper manufacturingFood industryCooling towerShip hulls, fishing farmsHeat exchangersWater desalination systems
Air Apparent 12 months
Fajun Zhang 309.12.2011
Marine biofouling systems Algae, barnacle, mussel,
Bacteria, proteins, etc.
Marine organisms and bacteria
Fajun Zhang 409.12.2011
Procedure of Biofouling
Extracellular Polymeric Substrances (EPS)
Fajun Zhang 509.12.2011
Strategy for anti-biofouling
Mechanical detachment of biofoulers if possible;Killing biofoulers using antibiotics, biocides, cleaning chemicals, etc.;
TBT-Silver Bullet: get rid of biofouling once and forever!Toxic, banned by the year 2008
tributyltin
Fajun Zhang 609.12.2011
Strategy for anti-biofouling
Surface engineering:Low energyLow adhesiveNon-sticking
S. Krishnan et al. J. Mater. Chem. 2008, 18, 3405
Fajun Zhang 709.12.2011
Surface Energy, the Work of Adhesion
Work can be expressed in terms of surface energies and interfacial energies
Contact angle θ
γsa =γls + γla cosθ
Young-Dupre equation
Fajun Zhang 809.12.2011
Surface Energy, the Work of Adhesion
For an organism (O) in aqueous medium (w) in the presence of a surface (S)
Wsow = -γso + γsw + γow
For dispersion forces
The work of adhesion can be expressed using contact angle as
Wsow = 1/2γw(1-cosθo)(1-cos θs)
Fajun Zhang 909.12.2011
Strategy I: low Energy hydrophilic surface
Wsow = 1/2γw(1-cosθo)(1-cos θs)According to the equation, as θs approaches zero (hydrophilic surface) the work of adhesion does too;
Fajun Zhang 1009.12.2011
Strategy I: low Energy hydrophilic surface
Interficial energy (work of adhesion) – Strong hydrophilic interface
Poly(ethlyene glycol) (PEG) self-assembled monolayer (SAM)OEG SAMVery low surface energy about 5 mJ/m2
The Baier curve, Andersson, et al., J. Marine Design, B84, 2003, 11
Fajun Zhang 1109.12.2011
OEG and PEG SAM: Preparation of SAM
Immersion
07.07.11 Swen Schuster ‐ Institute of Applied Physics 11
adsorption&
organisation
Au on Si wafer or SiO2 block for NR
~ 200‐500 μM Thiolsolution in Ethanol
12‐24h
M. Skoda
Fajun Zhang 1209.12.2011
Cell Adhesion
S. Schilp et al Langmuir 2009, 25, 10077
Fajun Zhang 1309.12.2011
competing interactions:
attractive:van der Waals:
hydrophobic attractionentropic (excluded volume)
repulsive (steric, entropic):
osmotic & elasticde/compression of PEG chainssolvation energy
long chains, high density
⎪⎭
⎪⎬⎫
⎪⎩
⎪⎨⎧
⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎟
⎠⎞
⎜⎝⎛+
⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎟
⎠⎞
⎜⎝⎛
⎟⎟⎠
⎞⎜⎜⎝
⎛=
Δ 1751
57 4/7
04/5
06/1112/5
1
221
LL
LLN
kk
ak
kTFs σ
⎟⎠⎞
⎜⎝⎛
++
++−=
ΔRd
dRd
RdR
kTA
kTFs
2ln
26
Jeon, S.I.; Andrade J.D.; de Gennes, P.G., J.Colloid Interface Sci. 1991, 142, 159
Steric Repulsion of Poly-EG
Fajun Zhang 1409.12.2011
l o n g chains
conformational changes
hydration
Additional ‘steric’repulsion
short chains
Pure low interfacial energy
PEG e.g. HS-(CH2)11-(EG)3
Fajun Zhang 1509.12.2011
Strategy II: low Modulus x Energy
Only consider the interfacial energy, we have:Wsow = 1/2γw(1-cosθo)(1-cos θs)An organism cannot distinguish a hydrophilic surface from a watery environment and attaches preferentially to a hydrophobic surfaceNow we consider also the mechanical property of the coating materials:
Fajun Zhang 1609.12.2011
Wsow = 1/2γw(1-cosθo)(1-cos θs)
Peeling force: P~(Eγ)1/2
Detaching by the weight of fouling materialsDetaching by shearing/weightPDMS (polydimethylsiloxane)
Strategy II: low Modulus x Energy
Siloxane elastomer coatinghydrophobic
Surface energy ~50 mJ/m2
Fajun Zhang 1709.12.2011
Strategy III: Non-sticking structured interfacesurface roughness, 3D patterning, energy and modulus
Surface roughness leads to superhydrophobicLow hysterisis of contact angleLow friction, reduction of drag in fluid flow
Lotus leafShark skin
dermal denticles ribbed with longitudinal grooves.
Reduce vortices formation,Water flow more efficiently
Protection from marine fouling: against adhesion and growth of
organisms
Fajun Zhang 1809.12.2011
Strategy III: Non-sticking structured interfacesurface roughness, 3D patterning, energy and modulus
Fajun Zhang 1909.12.2011
SummaryBiofouling is a complex procedure involving chemical, physical and biological processes. Current strategy focus on surface engineering:
Low interfacial energy: strong hydrophilic (water like)Low modulus and energy (elastomers): weak peeling force3D structure: disturbing the settlement of marine organisms
