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Rahmaninejad H, Parnell AJ, Chen WL, Duzen N, Sexton T, Dunderdale G, Ankner JF, Bras W, Ober CK, Ryan AJ, Ashkar R. Synthesis and Characterization of Stimuli-Responsive Polymer Brushes in Nanofluidic Channels. ACS APPLIED MATERIALS & INTERFACES 2023; 15:54942-54951. [PMID: 37973616 PMCID: PMC10695172 DOI: 10.1021/acsami.3c12744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 10/20/2023] [Accepted: 11/01/2023] [Indexed: 11/19/2023]
Abstract
Nanochannels with controllable gating behavior are attractive features in a wide range of nanofluidic applications including viral detection, particle sorting, and flow regulation. Here, we use selective sidewall functionalization of nanochannels with a polyelectrolyte brush to investigate the channel gating response to variations in solution pH and ionic strength. The conformational and structural changes of the interfacial brush layer within the channels are interrogated by specular and off-specular neutron reflectometry. Simultaneous fits of the specular and off-specular signals, using a dynamical theory model and a fitting optimization protocol, enable detailed characterization of the brush conformations and corresponding channel geometry under different solution conditions. Our results indicate a collapsed brush state under basic pH, equivalent to an open gate, and an expanded brush state representing a partially closed gate upon decreasing the pH and salt concentration. These findings open new possibilities in noninvasive in situ characterization of tunable nanofluidics and lab-on-chip devices with advanced designs and improved functionality.
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Affiliation(s)
- Hadi Rahmaninejad
- Department
of Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
- Center
for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Andrew J. Parnell
- Department
of Physics, The University of Sheffield, Sheffield S3 7RH, U.K.
| | - Wei-Liang Chen
- Department
of Material Science and Engineering, University
of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Nilay Duzen
- Department
of Material Science and Engineering, Cornell
University, Ithaca, New York 14850, United States
| | - Thomas Sexton
- Department
of Physics, The University of Sheffield, Sheffield S3 7RH, U.K.
| | - Gary Dunderdale
- Department
of Chemical and Biological Engineering, The University of Sheffield, Sheffield S1 3JD, U.K.
| | - John F. Ankner
- Second
Target Station, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Wim Bras
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Christopher K. Ober
- Department
of Material Science and Engineering, Cornell
University, Ithaca, New York 14850, United States
| | - Anthony J. Ryan
- Department
of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K.
| | - Rana Ashkar
- Center
for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
- Department
of Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
- Macromolecular Innovation Institute, Virginia
Tech, Blacksburg, Virginia 24061, United States
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Feng H, Ashkar R, Steinke N, Dalgliesh R, Lavrik NV, Kravchenko II, Pynn R. Grating-based holographic diffraction methods for X-rays and neutrons: phase object approximation and dynamical theory. J Appl Crystallogr 2018. [DOI: 10.1107/s1600576717016867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography. It is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. While the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.
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Ashkar R, Pynn R, Dalgliesh R, Lavrik NV, Kravchenko II. A new approach for probing matter in periodic nanoconfinements using neutron scattering. J Appl Crystallogr 2014. [DOI: 10.1107/s1600576714013387] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The efficacy of spin-echo small-angle neutron scattering (SESANS) combined with an exact dynamical theory (DT) model in resolving the arrangement of spherical colloidal particles in planar confinements, such as the channels of a rectangular diffraction grating, is reported. SESANS data obtained with a suspension of charge-stabilized 180 nm silica particles in contact with a silicon diffraction grating, with ∼650 nm-wide channels, show clear deviations from the signal expected from a homogenous distribution of the suspension. DT fits to the data indicate that the colloidal particles are almost twice as concentrated in the channels as they are in the neighboring bulk suspension, consistent with a structure in which the particles are arranged in close-packed sheets parallel to the walls of the confining channels.
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