Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient

Theneyur Narayanaswamy Banuprasad, Thamarasseril Vijayan Vinay, Cherumannil Karumuthil Subash, Soney Varghese, Sajan D. George, Subramanyan Namboodiri Varanakkottu

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this "transport zone" wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.

Original languageEnglish
Pages (from-to)28046-28054
Number of pages9
JournalACS Applied Materials and Interfaces
Volume9
Issue number33
DOIs
Publication statusPublished - 23-08-2017

Fingerprint

Wetting
Contact angle
Hysteresis
Water
Temperature
Force measurement
Coalescence
Microfluidics
Thermal gradients
Cleaning
Polymers
Fabrication
poly-N-isopropylacrylamide

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Cite this

Banuprasad, Theneyur Narayanaswamy ; Vinay, Thamarasseril Vijayan ; Subash, Cherumannil Karumuthil ; Varghese, Soney ; George, Sajan D. ; Varanakkottu, Subramanyan Namboodiri. / Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient. In: ACS Applied Materials and Interfaces. 2017 ; Vol. 9, No. 33. pp. 28046-28054.
@article{1591da15f010409dbb463b456f696e73,
title = "Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient",
abstract = "In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this {"}transport zone{"} wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.",
author = "Banuprasad, {Theneyur Narayanaswamy} and Vinay, {Thamarasseril Vijayan} and Subash, {Cherumannil Karumuthil} and Soney Varghese and George, {Sajan D.} and Varanakkottu, {Subramanyan Namboodiri}",
year = "2017",
month = "8",
day = "23",
doi = "10.1021/acsami.7b07451",
language = "English",
volume = "9",
pages = "28046--28054",
journal = "ACS applied materials & interfaces",
issn = "1944-8244",
publisher = "American Chemical Society",
number = "33",

}

Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient. / Banuprasad, Theneyur Narayanaswamy; Vinay, Thamarasseril Vijayan; Subash, Cherumannil Karumuthil; Varghese, Soney; George, Sajan D.; Varanakkottu, Subramanyan Namboodiri.

In: ACS Applied Materials and Interfaces, Vol. 9, No. 33, 23.08.2017, p. 28046-28054.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient

AU - Banuprasad, Theneyur Narayanaswamy

AU - Vinay, Thamarasseril Vijayan

AU - Subash, Cherumannil Karumuthil

AU - Varghese, Soney

AU - George, Sajan D.

AU - Varanakkottu, Subramanyan Namboodiri

PY - 2017/8/23

Y1 - 2017/8/23

N2 - In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this "transport zone" wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.

AB - In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this "transport zone" wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.

UR - http://www.scopus.com/inward/record.url?scp=85028054438&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85028054438&partnerID=8YFLogxK

U2 - 10.1021/acsami.7b07451

DO - 10.1021/acsami.7b07451

M3 - Article

AN - SCOPUS:85028054438

VL - 9

SP - 28046

EP - 28054

JO - ACS applied materials & interfaces

JF - ACS applied materials & interfaces

SN - 1944-8244

IS - 33

ER -