scholarly journals Controlling nanochannel orientation and dimensions in graphene-based nanofluidic membranes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Muchun Liu ◽  
Paula J. Weston ◽  
Robert H. Hurt
Keyword(s):  
High Selectivity ◽  
Layered Materials ◽  
Membrane Thickness ◽  
Nanofluidic Channels ◽  
Thin Sectioning ◽  
Nanofluidic Devices ◽  
Vertically Aligned ◽  
Planar Membranes ◽  
Pronounced Reduction ◽  
Directional Transport

AbstractThere is great interest in exploiting van der Waals gaps in layered materials as nanofluidic channels. Graphene oxide (GO) nanosheets are known to spontaneously assemble into stacked planar membranes with transport properties that are highly selective to molecular structure. Use of conventional GO membranes in liquid-phase applications is often limited by low flux values, due to intersheet nanochannel alignment perpendicular to the desired Z-directional transport, which leads to circuitous fluid pathways that are orders of magnitude longer than the membrane thickness. Here we demonstrate an approach that uses compressive instability in Zr-doped GO thin films to create wrinkle patterns that rotate nanosheets to high angles. Capturing this structure in polymer matrices and thin sectioning produce fully dense membranes with arrays of near-vertically aligned nanochannels. These robust nanofluidic devices offer pronounced reduction in fluid path-length, while retaining the high selectivity for water over non-polar molecules characteristic of GO interlayer nanochannels.

scholarly journals ULTRASTRUCTURE AND CALCIUM TRANSPORT IN CRUSTACEAN MUSCLE MICROSOMES

1971 ◽  
Vol 48 (1) ◽  
pp. 49-60 ◽  
Author(s):  
R. J. Baskin
Keyword(s):  
Freeze Drying ◽  
Calcium Uptake ◽  
Membrane Thickness ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Crustacean Muscle ◽  
Thin Sectioning ◽  
Critical Point Drying ◽  
Freeze Etching ◽  
Microscopic Techniques

Fragmented sarcoplasmic reticulum (FSR) from crustacean muscle was examined following preparation by a variety of electron microscopic techniques. The 30–40 A particles which appeared on the outer surface of FSR vesicles following negative staining were not observed following preparation by freeze-drying, freeze-etching, thin sectioning, or critical-point drying. Crustacean FSR exhibited high values of calcium uptake and extensive nodular formation in the presence of oxalate. 80–90 A diameter membrane particles were seen in freeze-etch preparations of both intact lobster muscle and FSR vesicles. Thin sections of FSR vesicles revealed a membrane thickness of 60–70 A. The membrane appeared to be triple layered, each layer having a thickness of 20–25 A.

Mechanical exfoliation of track-etched two-dimensional layered materials for the fabrication of ultrathin nanopores

2014 ◽  
Vol 50 (91) ◽  
pp. 14149-14152 ◽  
Author(s):  
Yanan Jiang ◽  
Jun Gao ◽  
Wei Guo ◽  
Lei Jiang
Keyword(s):  
Layered Materials ◽  
Two Dimensional ◽  
Mechanical Exfoliation ◽  
Nanofluidic Devices

Mechanical exfoliation of ion-track-etched two-dimensional layered materials yields nanometer-thin nanoporous sheets that can be suspended atop a silicon window to controllably fabricate single- or multi-pore nanofluidic devices.

scholarly journals Scalable integration of nano-, and microfluidics with hybrid two-photon lithography

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Oliver Vanderpoorten ◽  
Quentin Peter ◽  
Pavan K. Challa ◽  
Ulrich F. Keyser ◽  
Jeremy Baumberg ◽  
...  
Keyword(s):  
Single Molecule ◽  
Super Resolution ◽  
Device Fabrication ◽  
Successful Operation ◽  
Force Microscopy ◽  
Two Photon ◽  
Nanofluidic Channels ◽  
Atomic Force ◽  
Nanofluidic Devices ◽  
Nanofluidic Device

Abstract Nanofluidic devices have great potential for applications in areas ranging from renewable energy to human health. A crucial requirement for the successful operation of nanofluidic devices is the ability to interface them in a scalable manner with the outside world. Here, we demonstrate a hybrid two photon nanolithography approach interfaced with conventional mask whole-wafer UV-photolithography to generate master wafers for the fabrication of integrated micro and nanofluidic devices. Using this approach we demonstrate the fabrication of molds from SU-8 photoresist with nanofluidic features down to 230 nm lateral width and channel heights from micron to sub-100 nm. Scanning electron microscopy and atomic force microscopy were used to characterize the printing capabilities of the system and show the integration of nanofluidic channels into an existing microfluidic chip design. The functionality of the devices was demonstrated through super-resolution microscopy, allowing the observation of features below the diffraction limit of light produced using our approach. Single molecule localization of diffusing dye molecules verified the successful imprint of nanochannels and the spatial confinement of molecules to 200 nm across the nanochannel molded from the master wafer. This approach integrates readily with current microfluidic fabrication methods and allows the combination of microfluidic devices with locally two-photon-written nano-sized functionalities, enabling rapid nanofluidic device fabrication and enhancement of existing microfluidic device architectures with nanofluidic features.

Nanofluidic Devices for Sensing and Flow Control

2006 ◽  
Author(s):  
Rohit Karnik ◽  
Kenneth Castelino ◽  
Chuanhua Duan ◽  
Rong Fan ◽  
Peidong Yang ◽  
...  
Keyword(s):  
Flow Control ◽  
Surface Charge ◽  
Gate Voltage ◽  
Field Effect ◽  
Electrostatic Interactions ◽  
Debye Length ◽  
Electrical Conductance ◽  
Nanofluidic Channels ◽  
Nanofluidic Devices ◽  
High Concentrations

Nanofluidics is concerned with fluidic channels that are typically 1–100 nm in size. We have fabricated nanofluidic devices using both 1-D silica nanotubes and 2-D nanochannels to explore transport phenomena at the nanoscale. Here we review our work on 2-D nanochannels that provide confinement in one dimension. Our work mainly deals with two aspects of nanofluidics (a) effects related to electrostatic interactions and (b) effects related to biomolecule size. Surface charge plays an important role in nanofluidic channels, when the channel size is comparable to the Debye length. Using both electrical conductance measurements and fluorescence imaging, we studied the effects of surface charge in our nanofluidic devices, and demonstrated that the environment in nanochannels is governed by surface charge. We modified the nanochannel surface and showed that these modifications can be sensed by measuring ionic conductance of the nanochannels. Further, binding reactions involving biomolecules can be sensed at both low and high ionic concentrations. Our results showed that at low concentrations, conductance is governed by biomolecule charge, while at high concentrations it is governed by biomolecule size. Based on electrostatic effects in nanochannels, we also developed a nanofluidic transistor for flow control. This metal-oxide-solution field effect transistor was fabricated by patterning a metal gate electrode over nanochannels, similar to a MOSFET. Just as the gate voltage of a MOSFET controls carrier concentration in the semiconductor, we demonstrated that the gate voltage in a nanofluidic transistor controls the concentration of ions and biomolecules in the nanochannel, and hence controls their transport. Our fabrication process uses standard lithography, and is amenable to making networks of nanochannels. It suggests that rationally designed nanofluidic networks could be developed using this process for applications in sample preparation, sensing and switching. We are currently studying flow control and switching using field-effect, as well as ionic transport using patterned surface charge in nanofluidic devices.

Optical DNA mapping in nanofluidic devices: principles and applications

Lab on a Chip ◽  
2017 ◽  
Vol 17 (4) ◽  
pp. 579-590 ◽  
Author(s):  
Vilhelm Müller ◽  
Fredrik Westerlund
Keyword(s):  
Dna Mapping ◽  
Nanofluidic Channels ◽  
Nanofluidic Devices ◽  
Novel Applications

This review describes the principles of optical DNA mapping in nanofluidic channels and highlights recent examples of exciting novel applications.

Mesoscale Thin Film Actuator for Promoting Fluid Motion in Microfluidic and Nanofluidic Channels

2002 ◽  
Vol 741 ◽  
Author(s):  
Daniel J. Sadler ◽  
Gaurav Singh ◽  
Frederic Zenhausern ◽  
Ravi F. Saraf
Keyword(s):  
Thin Film ◽  
Fluid Motion ◽  
Microfluidic Channel ◽  
Microfluidic Mixing ◽  
Spin Casting ◽  
Nanofluidic Channels ◽  
Nanofluidic Devices ◽  
Small Channels ◽  
Diffusive Mixing ◽  
Film Polymer

ABSTRACTMicrofluidic and nanofluidic devices often require actuators to induce fluid motion for applications such as pumping and mixing in small channels. Mixing, for instance, is important in systems where channel or chamber dimensions are on the order of 100 μm or larger as diffusive mixing can be prohibitively slow at these dimensions. In this work, a new mesoscale thin film polymer electromechanical actuator is introduced for use in the aforementioned applications. Unlike inorganic piezoelectric actuators, the devices based on these materials will be relatively easy to fabricate involving no high temperature processing, crystal growth, or microlithography. Fabrication of an array of actuators is simply achieved by spin casting the polymer over top of lithographically patterned gold electrodes at a thickness of less than 50 nm. This simple process enables a microfluidic device based on these actuators to be an integral part of a microfluidic channel rather than a separate unit operation. Depending on the application, the actuator array can be designed and controlled for random perturbations of the fluid flow field as required for mixing or for systematic actuation as required for pumping. These thin-film mesoscale actuators have been characterized and show extremely favorable properties such as a high electrostrictive response (compared to none in the bulk) and a frequency response of up to 50 kHz. In addition, finite element simulations show feasibility of these actuators for use in microfluidic mixing applications.

Preparatory Procedures for Electron Microscopic Analysis at the Molecular Level of Resolution

1978 ◽  
Vol 36 (3) ◽  
pp. 516-520
Author(s):  
F.J. Sjostrand
Keyword(s):  
Electron Microscope ◽  
Molecular Level ◽  
Microscopic Analysis ◽  
Resolving Power ◽  
Cellular Structures ◽  
Electron Microscopic ◽  
Systematic Analysis ◽  
Technical Developments ◽  
Thin Sectioning ◽  
Obvious Reason

In the 1940's and 1950's electron microscopy conferences were attended with everybody interested in learning about the latest technical developments for one very obvious reason. There was the electron microscope with its outstanding performance but nobody could make very much use of it because we were lacking proper techniques to prepare biological specimens. The development of the thin sectioning technique with its perfectioning in 1952 changed the situation and systematic analysis of the structure of cells could now be pursued. Since then electron microscopists have in general become satisfied with the level of resolution at which cellular structures can be analyzed when applying this technique. There has been little interest in trying to push the limit of resolution closer to that determined by the resolving power of the electron microscope.

Lead aspartate: a new en bloc stain for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 34-35
Author(s):  
J.R. Walton
Keyword(s):  
Electron Microscopy ◽  
Calcium Ion ◽  
Enzyme Reaction ◽  
Lead Citrate ◽  
Reaction Products ◽  
En Bloc ◽  
Thin Sections ◽  
Lead Salts ◽  
Thin Sectioning ◽  
High Alkalinity

In electron microscopy, lead is the metal most widely used for enhancing specimen contrast. Lead citrate requires a pH of 12 to stain thin sections of epoxy-embedded material rapidly and intensively. However, this high alkalinity tends to leach out enzyme reaction products, making lead citrate unsuitable for many cytochemical studies. Substitution of the chelator aspartate for citrate allows staining to be carried out at pH 6 or 7 without apparent effect on cytochemical products. Moreover, due to the low, controlled level of free lead ions, contamination-free staining can be carried out en bloc, prior to dehydration and embedding. En bloc use of lead aspartate permits the grid-staining step to be bypassed, allowing samples to be examined immediately after thin-sectioning.Procedures. To prevent precipitation of lead salts, double- or glass-distilled H20 used in the stain and rinses should be boiled to drive off carbon dioxide and glassware should be carefully rinsed to remove any persisting traces of calcium ion.

Albumins as Embedding Media for Electron Microscopy

1969 ◽  
Vol 27 ◽  
pp. 422-423 ◽  
Author(s):  
J. L. Farrant ◽  
J. D. McLean
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Temperature ◽  
Biological Material ◽  
Globular Proteins ◽  
The Past ◽  
Antibody Staining ◽  
Thin Sectioning ◽  
Embedding Medium

For electron microscope techniques such as ferritin-labeled antibody staining it would be advantageous to have available a simple means of thin sectioning biological material without subjecting it to lipid solvents, impregnation with plastic monomers and their subsequent polymerization. With this aim in view we have re-examined the use of protein as an embedding medium. Gelatin which has been used in the past is not very satisfactory both because of its fibrous nature and the high temperature necessary to keep its solutions fluid. We have found that globular proteins such as the serum and egg albumins can be cross-linked so as to yield blocks which are suitable for ultrathin sectioning.

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