TY - JOUR
T1 - Large-amplitude, reversible, pH-triggered wetting transitions enabled by layer-by-layer films
AU - Lu, Yiming
AU - Sarshar, Mohammad Amin
AU - Du, Ke
AU - Chou, Tsengming
AU - Choi, Chang Hwan
AU - Sukhishvili, Svetlana A.
PY - 2013/12/11
Y1 - 2013/12/11
N2 - We report on the use of layer-by-layer (LbL) hydrogels, composed of amphiphilic polymers that undergo reversible collapse-dissolution transition in solutions as a function of pH, to induce sharp, large-amplitude wetting transition at microstructured surfaces. Surface hydrogels were composed of poly(2-alkylacrylic acids) (PaAAs) of varied hydrophobicity, i.e., poly(methacrylic acid) (PMAA), poly(2-ethylacrylic acid) (PEAA), poly(2-n-propylacrylic acid) (PPAA) and poly(2-n-butylacrylic acid) (PBAA). When deposited at a micropillar-patterned silicon substrate, hydrophilic PMAA LbL hydrogels supported complete surface wetting (contact angle, CA, of 0), whereas PEAA, PPAA, and PBAA ultrathin coatings supported large-amplitude wetting transitions, with CA changes from 110 to 125 at acidic to 0 at basic pH values, and the transition pH increasing from 6.2 to 8.4 with increased polyacid hydrophobicity. At acidic pHs, droplets showed a large hysteresis in CA (a "sticky droplet" behavior), and remained in the Wenzel state. The fact that CA changes for wetting-nonwetting transitions occurred at values close to physiologic pH makes these coatings promising for controlling flow and bioadhesion using external stimuli. Finally, we show that the surface wettability transitions can be used to detect positively charged analytes (such as gentamicin) in solution via large changes in CA associated with adsorption of analytes within the hydrogels.
AB - We report on the use of layer-by-layer (LbL) hydrogels, composed of amphiphilic polymers that undergo reversible collapse-dissolution transition in solutions as a function of pH, to induce sharp, large-amplitude wetting transition at microstructured surfaces. Surface hydrogels were composed of poly(2-alkylacrylic acids) (PaAAs) of varied hydrophobicity, i.e., poly(methacrylic acid) (PMAA), poly(2-ethylacrylic acid) (PEAA), poly(2-n-propylacrylic acid) (PPAA) and poly(2-n-butylacrylic acid) (PBAA). When deposited at a micropillar-patterned silicon substrate, hydrophilic PMAA LbL hydrogels supported complete surface wetting (contact angle, CA, of 0), whereas PEAA, PPAA, and PBAA ultrathin coatings supported large-amplitude wetting transitions, with CA changes from 110 to 125 at acidic to 0 at basic pH values, and the transition pH increasing from 6.2 to 8.4 with increased polyacid hydrophobicity. At acidic pHs, droplets showed a large hysteresis in CA (a "sticky droplet" behavior), and remained in the Wenzel state. The fact that CA changes for wetting-nonwetting transitions occurred at values close to physiologic pH makes these coatings promising for controlling flow and bioadhesion using external stimuli. Finally, we show that the surface wettability transitions can be used to detect positively charged analytes (such as gentamicin) in solution via large changes in CA associated with adsorption of analytes within the hydrogels.
KW - layer-by-layer
KW - stimuli-responsive
KW - surface hydrogels
KW - weak polyelectrolytes
KW - wettability
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U2 - 10.1021/am403944m
DO - 10.1021/am403944m
M3 - Article
AN - SCOPUS:84890529770
SN - 1944-8244
VL - 5
SP - 12617
EP - 12623
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 23
ER -