Tag Archives: Morteza Miansari

Using acoustic waves to move fluids at the nanoscale

A Nov. 14, 2016 news item on ScienceDaily describes research that could lead to applications useful for ‘lab-on-a-chip’ operations,

A team of mechanical engineers at the University of California San Diego [UCSD] has successfully used acoustic waves to move fluids through small channels at the nanoscale. The breakthrough is a first step toward the manufacturing of small, portable devices that could be used for drug discovery and microrobotics applications. The devices could be integrated in a lab on a chip to sort cells, move liquids, manipulate particles and sense other biological components. For example, it could be used to filter a wide range of particles, such as bacteria, to conduct rapid diagnosis.

A Nov. 14, 2016 UCSD news release (also on EurrekAlert), which originated the news item, provides more information,

The researchers detail their findings in the Nov. 14 issue of Advanced Functional Materials. This is the first time that surface acoustic waves have been used at the nanoscale.

The field of nanofluidics has long struggled with moving fluids within channels that are 1000 times smaller than the width of a hair, said James Friend, a professor and materials science expert at the Jacobs School of Engineering at UC San Diego. Current methods require bulky and expensive equipment as well as high temperatures. Moving fluid out of a channel that’s just a few nanometers high requires pressures of 1 megaPascal, or the equivalent of 10 atmospheres.

Researchers led by Friend had tried to use acoustic waves to move the fluids along at the nano scale for several years. They also wanted to do this with a device that could be manufactured at room temperature.

After a year of experimenting, post-doctoral researcher Morteza Miansari, now at Stanford, was able to build a device made of lithium niobate with nanoscale channels where fluids can be moved by surface acoustic waves. This was made possible by a new method Miansari developed to bond the material to itself at room temperature.  The fabrication method can be easily scaled up, which would lower manufacturing costs. Building one device would cost $1000 but building 100,000 would drive the price down to $1 each.

The device is compatible with biological materials, cells and molecules.

Researchers used acoustic waves with a frequency of 20 megaHertz to manipulate fluids, droplets and particles in nanoslits that are 50 to 250 nanometers tall. To fill the channels, researchers applied the acoustic waves in the same direction as the fluid moving into the channels. To drain the channels, the sound waves were applied in the opposite direction.

By changing the height of the channels, the device could be used to filter a wide range of particles, down to large biomolecules such as siRNA, which would not fit in the slits. Essentially, the acoustic waves would drive fluids containing the particles into these channels. But while the fluid would go through, the particles would be left behind and form a dry mass. This could be used for rapid diagnosis in the field.

Here’s a link to and a citation for the paper,

Acoustic Nanofluidics via Room-Temperature Lithium Niobate Bonding: A Platform for Actuation and Manipulation of Nanoconfined Fluids and Particles by Morteza Miansari and James R. Friend. Advanced Functional Materials DOI: 10.1002/adfm.201602425 Version of Record online: 20 SEP 2016
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

They do have an animation sequence illustrating the work but it could be considered suggestive and is, weirdly, silent,

 

 

Graphene oxide in liquid crystal droplets could be used in medical applications

Not everyone has been seduced by all the talk of graphene and electronics, it seems researchers at Monash University in Australia have researched graphene with an eye to its potential use in medical applications. From an Aug. 6, 2014 news item on ScienceDaily,

A chance discovery about the ‘wonder material’ graphene — already exciting scientists because of its potential uses in electronics, energy storage and energy generation — takes it a step closer to being used in medicine and human health.

Researchers from Monash University have discovered that graphene oxide sheets can change structure to become liquid crystal droplets spontaneously and without any specialist equipment.

With graphene droplets now easy to produce, researchers say this opens up possibilities for its use in drug delivery and disease detection.

The findings, published in the journal ChemComm, build on existing knowledge about graphene. One of the thinnest and strongest materials known to man, graphene is a 2D sheet of carbon just one atom thick. With a ‘honeycomb’ structure the ‘wonder material’ is 100 times stronger than steel, highly conductive and flexible.

An Aug. 6, 2014 Monash University media release (also on EurekAlert but dated Aug. 5, 2014), which originated the news item, describes the findings in more detail,

Dr Mainak Majumder from the Faculty of Engineering said because graphene droplets change their structure in response to the presence of an external magnetic field, it could be used for controlled drug release applications.

“Drug delivery systems tend to use magnetic particles which are very effective but they can’t always be used because these particles can be toxic in certain physiological conditions,” Dr Majumder said.

“In contrast, graphene doesn’t contain any magnetic properties. This combined with the fact that we have proved it can be changed into liquid crystal simply and cheaply, strengthens the prospect that it may one day be used for a new kind of drug delivery system.”

Usually atomisers and mechanical equipment are needed to change graphene into a spherical form. In this case all the team did was to put the graphene sheets in a solution to process it for industrial use. Under certain pH conditions they found that graphene behaves like a polymer – changing shape by itself.

First author of the paper, Ms Rachel Tkacz from the Faculty of Engineering, said the surprise discovery happened during routine tests.

“To be able to spontaneously change the structure of graphene from single sheets to a spherical assembly is hugely significant. No one thought that was possible. We’ve proved it is,” Ms Tkacz said.

“Now we know that graphene-based assemblies can spontaneously change shape under certain conditions, we can apply this knowledge to see if it changes when exposed to toxins, potentially paving the way for new methods of disease detection as well.”

Commonly used by jewelers, the team used an advanced version of a polarised light microscope based at the Marine Biological Laboratory, USA, to detect minute changes to grapheme.

Dr Majumder said collaborating with researchers internationally and accessing some of the most sophisticated equipment in the world, was instrumental to the breakthrough discovery.

“We used microscopes similar to the ones jewelers use to see the clarity of precious gems. The only difference is the ones we used are much more precise due to a sophisticated system of hardware and software. This provides us with crucial information about the organisation of graphene sheets, enabling us to recognise these unique structures,” Dr Majumder said.

Dr Majumder and his team are working with graphite industry partner, Strategic Energy Resources Ltd and an expert in polarized light imaging, Dr. Rudolf Oldenbourg from the Marine Biological Laboratory, USA, to explore how this work can be translated and commercialised.

Here’s a link to and a citation for the paper,

pH dependent isotropic to nematic phase transitions in graphene oxide dispersions reveal droplet liquid crystalline phases by Rachel Tkacz, Rudolf Oldenbourg, Shalin B. Mehta, Morteza Miansari, Amitabh Verma, and Mainak Majumder. Chem. Commun., 2014,50, 6668-6671 DOI: 10.1039/C4CC00970C First published online 06 May 2014

This paper is behind a paywall.