Nav: Home

Learning how to fine-tune nanofabrication

February 14, 2017

Daniel Packwood, Junior Associate Professor at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS), is improving methods for constructing tiny "nanomaterials" using a "bottom-up" approach called "molecular self-assembly". Using this method, molecules are chosen according to their ability to spontaneously interact and combine to form shapes with specific functions. In the future, this method may be used to produce tiny wires with diameters 1/100,000th that of a piece of hair, or tiny electrical circuits that can fit on the tip of a needle.

Molecular self-assembly is a spontaneous process that cannot be controlled directly by laboratory equipment, so it must be controlled indirectly. This is done by carefully choosing the direction of the intermolecular interactions, known as "chemical control", and carefully choosing the temperature at which these interactions happen, known as "entropic control".

Researchers know that when entropic control is very weak, for example, molecules are under chemical control and assemble in the direction of the free sites available for molecule-to-molecule interaction. On the other hand, self-assembly does not occur when entropic control is much stronger than the chemical control, and the molecules remain randomly dispersed.

Until now, it's not been possible for researchers to guess what kinds of structures will result from molecular self-assembly when entropic control is neither weak nor strong compared to chemical control.

Packwood teamed up with colleagues in Japan and the U.S. to develop a computational method that allows them to simulate molecular self-assembly on metal surfaces while separating the effects of chemical and entropic controls.

This new computational method makes use of artificial intelligence to simulate how molecules behave when placed on a metal surface. Specifically, a "machine learning" technique is used to analyse a database of intermolecular interactions. This machine learning technique builds a model that encodes the information contained in the database, and in turn this model can predict the outcome of the molecular self-assembly process with high accuracy.

The team used this method to study the self-assembly of three different hydrocarbon molecules, the structures of which vary in the strength of the direction of their intermolecular interactions. In other words, they varied the strength of chemical control by changing the molecule under study.

While stronger chemical control caused molecules to assemble into chain-shaped structures, the effects of stronger entropic controls were found to be more counterintuitive. For example, they found that strengthening entropic control could transform large, disordered structures into several small, ordered, chain-shaped structures. They also showed that the formation of disordered structures results from weak chemical control rather than strong entropic control.

These predictions, which were verified by comparisons with high-resolution microscopic images of real molecules on metal surfaces, may lead to controlled, large-scale fabrication of tiny electrical wires and other nanomaterials for future devices. Devices made from nanomaterials would be significantly smaller and cheaper than existing electronics, and would have very long battery lives due to low energy consumption.

"By continued development of our code and theory, we expect to obtain increasingly detailed rules for controlling molecular self-assembly and aiding the bottom-up nanomaterials fabrication process," the researchers conclude in their study published in the journal Nature Communications.
The paper "Chemical and Entropic Control on the Molecular Self-Assembly Process" appeared on February 14, 2017 in Nature Communications, with doi: 10.1038/ncomms14463

The Institute for Integrated Cell-Material Sciences (iCeMS) at Kyoto University in Japan aims to advance the integration of cell and material sciences, both traditionally strong fields at the university, in a uniquely innovative global research environment. ICeMS combines the biosciences, chemistry, materials science and physics to create materials for mesoscopic cell control and cell-inspired materials. Such developments hold promise for significant advances in medicine, pharmaceutical studies, the environment and industry.

Kyoto University

Related Nanomaterials Articles:

Development of low-dimensional nanomaterials could revolutionize future technologies
Javier Vela, scientist at the US Department of Energy's Ames Laboratory, believes improvements in computer processors, TV displays and solar cells will come from scientific advancements in the synthesis of low-dimensional nanomaterials.
Researchers create first significant examples of optical crystallography for nanomaterials
Researchers at the University of Illinois at Urbana-Champaign have developed a novel way to determine crystal type based on optics -- by identifying the unique ways in which these crystals absorb light.
Researchers create anticancer nanomaterials by simulating underwater volcanic conditions
Researchers at Aalto University, Finland, have developed anticancer nanomaterials by simulating the volcano-induced dynamic chemistry of the deep ocean.
Utilizing tumor suppressor proteins to shape nanomaterials
A new method combining tumor suppressor protein p53 and biomineralization peptide BMPep successfully created hexagonal silver nanoplates, suggesting an efficient strategy for controlling the nanostructure of inorganic materials.
Direct radiolabeling of nanomaterials
Positron emission tomography plays a pivotal role for monitoring the distribution and accumulation of radiolabeled nanomaterials in living subjects.
New solution for making 2-D nanomaterials
Two-dimensional (2-D) nanomaterials have been made by dissolving layered materials in liquids, according to new UCL-led research.
Nanomaterials for neurology: State-of-the-art
Despite the numerous challenges associated with the application of nanotechnology in neuroscience, it promises to have a significant impact on our understanding of how the nervous system works, how it fails in disease, and the development of earlier and less-invasive diagnostic procedures so we can intervene in the preclinical stage of neurological disease before extensive neurological damage has taken place.
Can we find more benign nanomaterials?
University of Iowa chemist Sara Mason has won a grant to access a supercomputer network funded by the US National Science Foundation.
Application-safe and environmentally friendly development and use of nanomaterials
Thus BfR researchers have found out that pure silver nanoparticles are, following simulated digestion in the stomach and intestine, absorbed in much lower quantities than particles which are digested together with food components.
Notre Dame researchers find transition point in semiconductor nanomaterials
Collaborative research at Notre Dame has demonstrated that electronic interactions play a significant role in the dimensional crossover of semiconductor nanomaterials.

Related Nanomaterials Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Failure can feel lonely and final. But can we learn from failure, even reframe it, to feel more like a temporary setback? This hour, TED speakers on changing a crushing defeat into a stepping stone. Guests include entrepreneur Leticia Gasca, psychology professor Alison Ledgerwood, astronomer Phil Plait, former professional athlete Charly Haversat, and UPS training manager Jon Bowers.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".