Complete filling of batches of nanopipettes

January 08, 2020

Nanopipettes, in which a nanoscale channel is filled with a solution, are used in all kinds of nanotechnology applications, including scanning-probe microscopy. Bringing a solution into a nanopipette with a pore diameter below 10 nanometer is challenging, however, since capillary forces prevent the complete filling of a sub-10-nm nanopipette pore with a liquid. Now, Shinji Watanabe and colleagues from Kanazawa University have found a simple but efficient way for filling nanopipettes. The researchers show that the 'air bubble' that typically remains near the pipette's pore end can be removed by applying a temperature gradient along the pipette.

The scientists investigated their 'thermally-driven method' to a batch of 94 pipettes, aligned length-wise next to each other, all with a pore diameter of around 10 nm. The pipettes were put on a metal plate kept at a temperature of 80 °C, with their tips protruding from the plate, resulting in a temperature gradient.

Time-lapsed optical microscopy images of the filling process of the nanopipettes showed that after 1200 seconds, the tips are completely filled with solution, and that air bubbles are driven out of the pipettes.

In order to double-check that the pipettes were indeed bubble-free, Watanabe and colleagues performed so-called I-V measurements. Every pipette was filled with a solution of potassium chloride (KCl), which is conducting. Both pipette ends were then contacted with electrodes. If an electrical current runs between the ends -- specifically, if the pipette has an electrical conductivity below a few GΩ-- then filling with the solution is complete. The resesarchers observed electrical currents and therefore filling for the whole batch of pipettes.

The scientists also performed transmission electron microscopy (TEM) measurments of pipettes with pore diameters below 10 nm. Although the thermally-driven method leads to good electrical contacts, particle-like structures were observed inside the tips of the nanopipettes, demonstrating that (quoting the researchers) "TEM observation without inducing pipette deformation is important for accurately determining the characteristics of sub-10-nm nanopipettes."

Watanabe and colleagues concluded that their method is very practical and easy to introduce in nanopipette frabrication and that their study "will provide a significant contribution to various fields of nanoscience using nanopipettes.
This study was made available online in October 2019 ahead of publication in issue in November 2019.



Nanopipettes are pipettes, usually made from quartz or glass, with a pore opening in the nanometer range. Today, nanopipettes are used for various nanotechnology applications, including molecular sensing, delivery of chemicals, and scanning-probe microscopy. The latter is a technique for imaging a material's surface by scanning a probe over it; for the probe, a solution-filled nanopipette can be used.

The function of a nanopipette is usually to enable the transport, and their detection, of nanometer-sized objects (in solution) through the pipette pore.

Completely filling a nanopipette with a solution has been difficult: because of the capillary force, an 'air bubble' is nearly always present in the pipette's tip. Removing the air bubble has proven to be problematic for nanopipettes with a pore opening of 10 nanometer or less.

Now, Shinji Watanabe and colleagues from Kanazawa University have found a way to achieve complete filling of a batch of many nanopipettes with a pore opening of about 10 nm. The method, based on the application of a temperature gradient to the nanopipettes, is simple and efficient.

Kanazawa University

Related Temperature Articles from Brightsurf:

History of temperature changes in the Universe revealed
How hot is the Universe today? How hot was it before?

A drop in temperature
In the nearly two centuries since German physician Carl Wunderlich established 98.6°F as the standard ''normal'' body temperature, it has been used by parents and doctors alike as the measure by which fevers -- and often the severity of illness -- have been assessed.

Kitchen temperature supercurrents from stacked 2D materials
A 'stack' of 2D materials could allow for supercurrents at ground-breakingly warm temperatures, easily achievable in the household kitchen.

Get diamonds, take temperature
Measuring the temperature of objects at a nanometer-scale has been a long challenge, especially in living biological samples, because of the lack of precise and reliable nanothermometers.

Chemical thermometers take temperature to the nanometric scale
Scientists from the Coordination Chemistry Laboratory and Laboratory for Analysis and Architecture of Systems, both of the CNRS, recently developed molecular films that can measure the operating temperature of electronic components on a nanometric scale.

How reliable are the reconstructions and models for past temperature changes?
Understanding of climate changes during the past millennia is crucial for the scientific attribution of the current warming and the accurate prediction of the future climate change.

New method measures temperature within 3D objects
University of Wisconsin-Madison engineers have made it possible to remotely determine the temperature beneath the surface of certain materials using a new technique they call depth thermography.

Who takes the temperature in our cells?
The conditions in the environment are subject to large fluctuations.

Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.

Thermal siphon effect: heat flows from low temperature to high temperature
In this work, researchers study (both thermal and electric) energy transport in physical networks that rewired from 2D regular lattices.

Read More: Temperature News and Temperature Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to