Hot article: Heterogeneous versus homogeneous crystal nucleation of hard spheres

Crystallization processes from a liquid are very present in our life, for example the freezing of water and formation of ice crystals. In such processes, building blocks suspended in a fluid arrange themselves to form a crystal. Espinosa et al. focus on the case where these building blocks are hard spherical particles.

In a real-life situation, the liquid will normally be confined within certain walls – e.g. inside a container or on top of a surface. Therefore, some of the particles will interact with the walls and might Graphical abstract.form a small crystal (or nucleus) at its surface – the so-called heterogeneous nucleation. This is more favourable than generating a crystal in the bulk of the liquid (homogeneous nucleation), as it reduces the surface area of the crystal and thus the energy required to form it. In this work, the authors study the competition between both nucleation mechanisms. They carry out molecular dynamics simulations to model heterogeneous nucleation processes and compare with existing homogeneous nucleation numerical data. This enables them to identify two regimes depending on the density of the system, and in each of them a different nucleation mechanism is prevalent. When the number of particles in the liquid is not too high (less than 53% in volume), heterogeneous nucleation prevails. But above that threshold homogeneous nucleation takes over.

This study not only provides further insights into the competition between nucleation mechanisms; the expected prevalence of heterogeneous nucleation in experimental conditions could be part of the explanation as to why experimental and modelling results in the field have often discrepancies.

Comments from the authors:
• Above a certain density, a fluid composed hard spheres arranged in a disordered fashion is less stable than a crystal where the spheres are packed as cannon balls.
• The first step of the transformation into the crystal is the emergence of crystal embryos (or nuclei) in the fluid.
• Crystal nuclei may appear in the fluid bulk (homogeneous nucleation) or on the walls of the cell containing the fluid (heterogeneous nucleation).
• Whereas walls are always present in experiments, simulations effectively eliminate them with a trick called “periodic boundary conditions” by which a sphere leaving the simulation box on one side enters from the opposite side like ghosts in the Pacman game.
• The simultaneous appearance of homogeneous and heterogeneous nuclei makes it difficult to measure homogeneous nucleation rates in experiments.
• The balance between homogeneous and heterogeneous nucleation depends on the size and the shape of the container and on the fluid density.
• Heterogeneous nucleation prevails in fluids where particles occupy less than ~ 54 per cent of the space in cells typically used in experiments.
• The dominance of heterogeneous nucleation could explain long-standing discrepancies between experimental measurements and simulation estimates of the homogeneous nucleation rate.
• A strategy based on coating the cells with spheres arranged in a fluid fashion could potentially eliminate heterogeneous nucleation in experiments.

Citation to the paper: Heterogeneous versus homogeneous crystal nucleation of hard spheres, Soft Matter, 2019, 15, 9625-9631, DOI: 10.1039/C9SM01142K
To read the full article click here!

About the web writer

Dr Ignacio Martin-Fabiani (@FabianiNacho) is a Vice-Chancellor’s Research Fellow at the Department of Materials, Loughborough University, UK.

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Award Winners at the 31st Society of Polymer Science, Japan-Research Group on Polymer Gels Symposium

Congratulations to award winners Siyuan Chen and Mousumi Akter (left and right of the photo, respectively) for their Soft Matter presentations at the “31st Society of Polymer Science, Japan-Research Group on Polymer Gels Symposium” held in Tokyo on 16th and 17th January 2020!

The Soft Matter presentation prizes were awarded by Chair of the event, Professor Akira Kakugo of Hokkaido University (middle of the photo).

Details of the winners can be seen below.

Siyuan Chen
Talk Title: “Protein-free insulin delivery microneedle patch integrated with temperature independent, glucose-responsive hydrogel”
Affiliation: Co-researcher at the Kanagawa Institute of Industrial Science and Technology and Researcher & Tokyo Medical and Dental University

Mousumi Akter
Talk Title: Photo-activated cargo transportation by molecular swarm robot
Affiliation: Hokkaido University

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May the force not be with the cancer cells

Scientists recently defined a cell-generated traction force threshold as a mechano-marker for the onset of cancer cell malignant transformation. Written by Mr Zhenwei Ma

Cancer metastasis is believed to be responsible for about 90% cancer mortality1. Despite tremendous efforts that have been devoted to identify biochemical markers for the onset of metastasis, the early diagnosis of malignant tumor remains challenging. Apart from interacting via biochemical signals with their surroundings, cancer cells are also actively generating forces and remodelling their mechanical microenvironment to survive and thrive, or even worse, to colonize new territories. In a recent paper published in Soft Matter, Zhang and others from the Pennsylvania State University established a traction force threshold that can be potentially used as a biomechanical marker for the onset of metastatic-like dispersion of cancer cells.

graphical abstract for the paper c9sm00733d

Spatiotemporal evolution of traction and intercellular tension in HCT-8 cell colonies cultured on soft and stiff hydrogel.

Upon prolonged culture of HCT-8 cells (a colon carcinoma cell line) on hydrogels with various stiffness, they found that their malignant transformation was both substrate stiffness and colony size dependent. HCT-8 colonies grown on soft hydrogels (2.6 kPa) remained cohesive throughout the two-week culture period. However, when cultured on stiffer substrates (20.7 kPa and 47.1 kPa), cells at the periphery started to disperse from their mother colony at day 7, until completely dispersed into individual cells at day 14. And size matters too. Dispersions in smaller colonies occurred earlier comparing to the larger ones.

Using traction force microscopy (TFM), researchers conducted a thorough study to correlate the cell-generated traction force with substrate stiffness and colony size. They revealed a fascinating spatiotemporal evolution of cellular forces during colony dispersion: cells on the verge generates critically higher traction forces comparing to colony interiors, ready to evade, until the onset of colony dispersion, where their forces start to decrease before completely vanished. Based on this traction force threshold, they further constructed a phase diagram to help predict colony cohesive/dispersive behaviour. When the force generated by the cells at colony boundary is big enough, they are more likely to metastasize. Interestingly, their dispersion behaviour could be efficiently suppressed by inhibiting their contractility, if treated at the right time.

The molecular mechanism behind remains to be further explored, but this study indicates the significant role of cell-generated forces in mediating cancer metastasis, which provides a new insight for the identification of early stage malignancy progression.

May the force not be with the cancer cells.

Reference:
1 Chaffer, C. L., & Weinberg, R. A. (2011). Science, 331(6024), 1559-1564.

 

Read the full article now for FREE until 31st October!

A traction force threshold signifies metastatic phenotypic change in multicellular epithelia

 

About the web writer

Zhenwei Ma is currently a Ph.D. candidate in Mechanical Engineering at McGill University. He holds a M.E. degree in Chemical Engineering at McGill University and a B.E. degree in Chemical Engineering from Sichuan University. Find out more about him here.

 

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Nominations now open for the 2020 Soft Matter Lectureship

Do you know an early-career researcher who deserves recognition for their contribution to the soft matter field?

Now is your chance to put them forward for the accolade they deserve!

Soft Matter is pleased to announce that nominations are now being accepted for the 2020 Soft Matter Lectureship award. This annual award was established in 2009 to honour an early-stage career scientist who has made a significant contribution to the soft matter field.

The recipient of the award will be asked to present a lecture at an international conference in 2020, where they will also be presented with the award. The Soft Matter Editorial Office will provide financial support to the recipient for travel and accommodation costs.

The recipient will also be asked to contribute a lead article to the journal and will have their work showcased free of charge on the front cover of the issue in which their article is published.

Tim White receiving his award from Dimitris Vlassopoulos and Laura Fisher

Prof Tim White receiving his Soft Matter Lectureship award from Professor Dimitris Vlassopoulos (left) and Laura Fisher (right)

 

Previous winners

2019 – Timothy J White, University of Colorado, USA

2018 – Susan Perkin, University of Oxford, UK

2017 – Daeyeon Lee, University of Pennsylvania, USA

2016 – Damien Baigl, Ecole Normale Supérieure, Paris, France

2015 – Lucio Isa, ETH Zürich, Switzerland

2014 – Eric Dufresne, Yale Univeristy, USA

2013 – Eric Furst, University of Delaware, USA

2012 – Patrick Doyle, MIT, USA

2011 – Michael J. Solomon, University of Michigan, USA

2010 – Bartosz Grzybowski, UNIST, Republic of Korea

2009 – Emanuela Zaccarelli, University of Rome, Italy

Eligibility

To be eligible for the lectureship, candidates should meet the following criteria:

  • Be an independent researcher, having completed PhD and postdoctoral studies
  • Be actively pursuing research within the soft matter field, and have made a significant contribution to the field
  • Be at an early stage of their independent career (this should be within 12 years of attaining their doctorate or equivalent degree, but appropriate consideration will be given to those who have taken a career break or followed an alternative study path)

Although the Soft Matter Lectureship doesn’t explicitly reward support of or contributions to the journal, candidates with no history of either publishing in or refereeing for the journal would typically not be considered.

Selection

  • Eligible nominated candidates will be notified of their nomination, and will be asked to provide 3 recent articles that they feel represent their current research.
  • All eligible nominated candidates will be assessed by a shortlisting panel, made up of members of the Soft Matter Advisory Board and a previous lectureship winner.
  • The shortlisting panel will consider the articles provided by the candidates as well as their CVs and letters of nomination.
  • Shortlisted candidates will be further assessed by the Soft Matter Editorial Board, and a winner will be selected based on an anonymous poll.
  • Selection is not based simply on quantitative measures. Consideration will be given to all information provided in the letter of recommendation and candidate CV, including research achievements and originality, contributions to the soft matter community, innovation, collaborations and teamwork, publication history, and engagement with Soft Matter.

Nominations

  • Nominations must be made via email to softmatter-rsc@rsc.org, and should include a short CV (3 page maximum length) and a brief letter of nomination (1 page maximum length)
  • Self-nomination is not permitted.
  • Nominators do not need to be senior researchers, and we encourage nominations from people at all career levels.
  • As part of the Royal Society of Chemistry, we believe we have a responsibility to promote inclusivity and accessibility in order to improve diversity. Where possible, we encourage each nominator to consider nominating candidates of all genders, races, and backgrounds.
  • Candidates outside of the stated eligibility criteria may still be considered.

Nominations should be submitted no later than 30th November 2019.

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Register now for ECIS 2019

The the 33rd Conference of the European Colloid and Interface Society (ECIS), will take place from the 8th to the 13th September 2019 at KU Leuven, Belgium.

Topics will cover fundamental and applied advances in the fields of dispersed systems, nanoparticles, self-assembly and supramolecular systems, as well as wetting and liquid interfaces. In addition, advances in theory, simulation, and instrumentation including new analytical techniques will be discussed. During the conference, plenary lectures will be given by the laureates of the Overbeek and Solvay Prizes and by other eminent speakers. Participation and advancement of young researchers and PhD students will be encouraged through the Enzo Ferroni Prize and several best poster prizes.

 

Conference banner for the ECIS

 

For more information and to register visit the conference website: https://kuleuvencongres.be/ecis2019/home

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Congratulations to Poster Prizewinners at The 2019 Graham Lecture and Symposium

Soft Matter was proud to sponsor 3 Poster Prizes at the recent Graham Lecture and Symposium, which took place in London on the 9th July and focused on the industrial and interdisciplinary applications of suspensions. Speakers presented on a wide range of applications, including ice cream, ceramics and paint, and on interdisciplinary topics, such as volcanoes. The awards were presented by Andrew Walton from Malvern Panalytical.

Ben Guy receiving his award

Ben Guy receives his award from Andrew Walton (Malvern Panalytical)

Rory O'Neill receiving his award

Rory O’Neill (University of Edinburgh) receives his award from Andrew Walton (Malvern Panalytical)

Soichiro Makino receiving his award

Soichiro Makino (University of Edinburgh) receives his award from Andrew Walton (Malvern Panalytical)

Congratulations to all three prize winners!

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Polydays 2019 – Polymer Science and Engineering in View of Digitalization

The Polydays 2019 conference, taking place in Berlin on the 11th – 13th September, will focus on the transformation of material research by digital technologies, initiated by the Berlin-Brandenburg Association of Polymer Research (BVP) and organized by the Helmholtz-Zentrum Geesthacht (HZG). The conference will be chaired by Prof. Andreas Lendlein (Institute of Biomaterial Science, HZG) and co-chaired by Prof. Hans Börner (Institute of Chemistry, Humboldt-Universität zu Berlin).

Confirmed plenary speakers:
– Amanda Barnard, CSIRO, Melbourne, Australia
– Andrew I. Cooper, University of Liverpool, UK
– Jean-François Lutz, CNRS-Institute Charles Sadron, Strasbourg, France
– E. W. (Bert) Meijer, Eindhoven University of Technology, Netherlands
– Roeland Nolte, Radboud University, The Netherlands
– H. Jerry Qi, Georgia Institute of Technology, Atlanta, USA

Key dates
12th July – abstract submission deadline
31st July – early bird registration deadline

For more information please refer to the conference webpage:  www.hzg.de/polydays2019

Polydays event flyer

 

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The 29th biennial meeting of the Institute of Physics Polymer Physics Group

The 29th biennial meeting of the Institute of Physics Polymer Physics Group will take place from 11-13 September 2019 at the University of Lincoln, UK.  The early registration deadline is 19 July 2019 and poster abstract submission will remain open until 23 August 2019.

 

The Founders’ Prize lecture will be given by Masao Doi (Beihang University, China), and the invited speakers (confirmed) are Rachel Evans (Cambridge, UK), Marie-Pierre Laborie (Freiburg, Germany), Juan de Pablo (Chicago, USA) and James Sharp (Nottingham, UK).

Please see the conference website http://paps19.iopconfs.org/home for further details.  The event is open to all with an interest.

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InterPore 2020

Mark your calendar: InterPore2020 will be held 25-28 May 2020 in Qingdao, China!

Topics covered include

  • Transport phenomena
  • Swelling and shrinking porous media
  • Multiphysics-multiphase flow
  • Reservoir engineering
  • Soil Mechanics and Engineering
  • Geothermal energy
  • CO2 sequestration
  • Constitutive modeling
  • Wave propagation
  • Energy Storage
  • Biotechnology
  • Biofilms
  • Thin and nanoscale poromechanics
  • Fuel cells and batteries
  • Food
  • Paper and textiles
  • Filters, foams, membranes
  • Fibers and composites
  • Ceramics and constructions materials
  • Other porous media applications

For more information please refer to the conference webpage.

Interpore Flyer

 

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2019 Lectureship awarded to Tim White at ISMC

Professor Tim White gave the 2019 Soft Matter Lecture and was presented with his Award at the International Soft Matter Conference in Edinburgh, which took place from the 3rd – 7th June. Professor White’s lecture was on ‘Pixelated Polymers: Programming Function into Liquid Crystalline Polymer Networks and Elastomers’.

 

Tim White receiving his award from Dimitris Vlassopoulos and Laura Fisher

Prof Tim White receiving his Soft Matter Lectureship award from Associate Editor Professor Dimitris Vlassopoulos (left) and Deputy Editor Laura Fisher (right) (©Paul Maguire)

 

Professor Tim White presenting his lecture at the ISMC

Professor Tim White presenting his lecture at the ISMC (©Paul Maguire)

 

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