December update

It’s been a busy term, so here’s the highlights:

I’ve had a “Secret Project” within CfAM for about a year now, developing a new technique for inkjet printing that grants us more fine control. It’s working, which is very exciting, but it’s working well enough that we’re considering IP protection. Which means although we’ve begun preparing a publication, it’s going back into the Secret Projects pile with the others.

I’m accelerating towards a publication in collaboration with Yinfeng He, a transitional professor in CfAM, centered on some exciting new multi-material printing. We’re one piece of data analysis and one mechanical test away from being done, with the paper already drafted around these, so we should be looking at mid January to early February.

I’m applying to a Nottingham Research Fellowship: a program intended to provide funding for 3 years on a proposed project, to act as a ‘kickstarter’ to an independent professorship. Competition is very stiff (I know many of my colleagues are applying as well, and they are quite impressive), so we’ll see how it goes. I’m excited for the opportunity, and I’m reassured that thanks to the discussions and connections that have come out of this process, even if I don’t get the role this year, I’m set up for some amazing opportunities over the next year.

I’ve taken on the role of Engineering Research Futures (ERF) rep within CfAM. ERF is a Nottingham organisation that facilitates and assists in career and personal development for our engineering researchers. This includes organising professional networking events, professional development resources, providing guidance, and taking feedback from researchers to then take to the Faculty. I’m taking over for the previous rep, Ian Maskery, who is an Nottingham Research Fellow in the process of transition into full professorship. If you’d like more details

And: I just had a visit from some family. My parents came to the UK for their first-ever trip to Europe, and stayed with us for a week. They were very endeared by the UK, and are currently in Switzerland ‘visiting’ the mountains. A very nice addition to the term.

Here’s to some new exciting publications in the coming months!

Solid Freeform Fabrication Symposium 2022

This week I’ve been in Austin Texas, attending the 2022 Solid Freeform Fabrication Symposium (SFF). It’s been a great week seeing many wonderful talks by global experts in additive manufacturing. I was there with several of my colleagues from the Centre for Additive manufacturing, all presenting their work, much of which has been recently published. I was there discussing my recent development of a highly reliable inkjet formulation of PEDOT:PSS conductive polymer, for which we currently have a paper under review (fingers crossed you’ll be hearing about it here soon!)

CfAM was represented by presentations from Daniel Padrao, Arielle Torres, Negar Gilani, Juan Francisco Reyes Luna, Jan-Hendrik Groth, Robert Plant, and myself, and we were all acommpanied and supported by Prof. Chris Tuck and Prof. Richard Hague.

Paper Roundup

Last year was fairly busy, with aftershocks from the pandemic, and preparations of publications that are currently in review, so I’m sorry to say I missed writing posts for some publications I had collaborated on.

The first is a review paper led by my PhD student, Maira Anam. It reviews the state of the art and trends regarding electrodes for bio-electrochemical cells (BESs). These BES devices are electrochemical reactors that use a population of bacteria to perform important chemical reactions, such as degrading pollutants or generating hydrogen. The bacteria live on an electrode, and the efficiency of the BES is directly tied to the health of the bacterial colony and its ability to electronically and electrochemically communicate with the electrode. This paper takes a special focus on a special sub set of BES, the bio-photovoltaic cell, which uses photosynthetic microbes to generate hydrogen ions, which then produce electricity through an integrated hydrogen fuel cell.
Maira and I are currently 3D-printing new electrodes for test-scale BPVs, as part of her thesis and my research. The review paper can be found here: https://doi.org/10.1039/D1SE00396H

The second paper was a large collaboration with Dr. Vincenzo Taresco, of the Dr. Steve Howdle Polymers & Supercritical Fluids Group, led by his PhD student Philippa L. Jacob. In this work a process for enzymatically-catalysed synthesis of poly(glycerol adipate) (PGA) variants from a variety of precursors resulted in fine control of the polymer functionality and properties. These were then evaluated for the formation of drug-delivery nanoparticles, providing a library of customisable polymers for nono-medicine. The paper can be found here: https://doi.org/10.1016/j.polymer.2021.123912

Collaborations with National Physical Laboratory

One of the perks of this job is getting analytical opportunties that are cutting edge. In the coming weeks I’ll fortunate to have some of my 3D-printed samples investigated by our colleagues at the National Physical Laboratory (NPL). For this, Dr. Gustavo F. Trindade, a Senior Research Scientist of NPL and a former co-worker of mine at CfAM, will be using ToF-OrbiSIMS to quantify what is happening at the interface of two of our sequentially-printed ink-jet electronic materials. A very exciting aspect of this study is that Dr. Trindade will be employing a new technique within the Tof-OrbiSIM, allowing him to investigate a junction between a soft and stiff material: a serious challenge. I can’t discuss the details of the method, but I’ve seen some preliminary results, and now I’m excited to see what my junctions look like and how we can better control them for higher quality electronics.

New Co-Authored Paper: Self Healing Polymers and Flexible Antennae

I'm very excited to announce that a new publication I’m proud to have been a part of has been accepted for publication by the Journal of Materials Chemistry A.  The work is "Triple non-covalent dynamic interactions enabled tough and rapid room temperature self-healing elastomer for next generation soft antenna", a clever use of multiple competing forms of molecular bonding to create a high-quality and self healing elastomer for use in the flexible electronics field. I was very happy to collaborate with the lead author, Pengxiang Si, while I was a member of the Surface Science and Bio-nanomaterials Lab Group in Waterloo, Ontario. Our article can be found through the following link:  (Click here to open the article site in a new window)

In this work, a carboxylate-containing polyurethane was synthesized and dispersed as a colloid into water doped with ammonium hydroxide. To this PEI was added; the ionic crosslinking reaction that would normally occur was prevented by the ammonium hydroxide, delaying the solidification process until the colloid was able to dry at room temperature. The resulting polymer was capable of self healing, 1000%+ elongation, and was then used to manufacture a self-healing flexible-stratchable radio antennae.

Round-Up: Two Publications

I’m excited to update that since last blog post I’ve had two publications accepted and published: one a co-authorship with members of my previous research group, and another a publication I led.

The first is “Multifunctional liquid crystal polymer network soft actuators” (Link), an impressive work led by Dr. Li Yu and Dr. Ran Peng. In this work we demonstrated the fabrication, programming, and function of actuators composed of liquid crystal polymers and liquid metals. These materials had been tuned to acheive strong mutual attraction, keeping the liquid metal confined within the liquid crystal encapsulation. The result was a thermally-driven actuator with stable electrical conductivity throughout its actuation range.

The second work published is “Cellulose Nanocrystal and Silver Nanobelt Gel: Cooperative Interactions Enabling Dispersion, Colloidal Gels, and Flexible Electronics“ (Link), led by myself and co-authored by Dr. Li Yu. In this work we investigated the formulation of a colloidal gel of silver nanobelts and cellulose nanocrystals. The carboxylic acid groups on the silver nanobelts and the hydroxyl groups on the cellulose nanocrystals formed a dynamic bonding structure that led to a shear-thinning gel, allowing proof of concept of a flexible conductor.

Thank you to Dr. Li Yu for collaborating with me for both these studies, it was a tremendous priviledge to work with him, and I look forward to our next opportunity.

Citation in Error

Please see this open letter to the Editors of International Journal of Intelligent Information and Management Science, regarding a citation in error.

I have not yet made direct contact with the editors, as I have been unable to find digital contact information (email, etc.). If you have contact information for this editorial board, I would be grateful to receive it.

2019-11-25

Editorial Board,

International Journal of Intelligent

Information and Management Science,

Dear Editors,

It has come to my attention that I have received a citation from an article published in your journal (Minyi Qian, Enterprise Strategic Adjustment based on Path Dependence Theory, International Journal of Intelligent Information and Management Science, ISSN: 2307-0692, Volume 8, Issue 3, June, 2019).  The citation is referencing my published manuscript (Rivers G., et al., “Vitrification during cure produces anomalies and path-dependence in electrical resistance of conductive composites” Composites Science and Technology. 2017, 149, 90-99).

The citation uses my publication as a reference to discuss the various forms of diversification strategy in business, relating to new and superior technology’s role in emerging markets, going into a great deal of detail of the various categories.  It is also related to Figure 2 of Minyi Qian’s article, which further discusses enterprise strategy.

It is my unfortunate duty to inform you that my manuscript is not a suitable citation for this topic.  The cited manuscript of my work is a materials science and engineering paper, discussing an interaction of polymer physics with the development of electrical conductivity during chemical cure processes.  It does not contain any definitions of categories of business strategy, or discussions of emerging market, that would support the authors published statements.  I believe the author may have cited my paper in error, intending to cite another more suitable in its place.

As regrettable as it is to lose a citation, I must request that you remove my manuscript from this citation list, publish a correction statement, and provide the author an opportunity to correct this oversight, for the integrity of their manuscript and your publication.

In the interest of transparency, I will be posting this as an open letter on my website.

Kind Regards,

Dr. Geoffrey Rivers

Research Fellow

Centre for Additive Manufacturing

University of Nottingham

New Co-Authored Research Manuscript Published

I'm very excited to announce that a new publication I’m proud to have been a part of has been released today in Nature Materials.  The work is "A hybrid material that reversibly switches between two stable solid states", a fantastic materials concept study. I was very happy to collaborate with the lead authors, Fut Kuo Yang and Aleksander Cholewinski, and to contribute my ideas and characterisation experience as they championed this new class of functional material. Our article can be found through the following link:  Read-Only PDF presented by Nature.com: https://rdcu.be/bLilY

In this work, a new class of sol-gel composite was designed from the bottom-up, employing a cross-linked polymer gel and sodium acetate: a salt with a low melting point and the ability to be super-cooled, colloquially known as “Hot Ice”. The polymer was selected and optimised to maximize the positive association between the salt and the polymer, resulting in a networked sol-gel that uses the salt as an ideal solvent. This results in a Sal-Gel: a new material that combines the phase-change properties of Hot Ice with the shape-maintaining properties of the polymer gel, achieving a material that can undergo a reversible change between two solid states that differ in stiffness by five orders of magnitude. This concept was then shown to be generalizable to other systems, applying the same design methods to arrive at another new combination: “sug-gel”. This demonstrates that this new concept is not limited to a single material combination, and in the future can be further engineered and optimised, leading to a family of functional, printable, property-shifting materials.

New Position Started, and New Manuscript Published

It’s been a busy couple of weeks, moving to the UK and starting my new post-doc at the University of Nottingham, while revising two manuscripts for submission. So busy I haven’t posted an update yet! So:

I’m pleased to announce that, as of July 1st, I began my new Post-Doc in the Centre for Additive Manufacturing (CfAM: https://www.nottingham.ac.uk/research/groups/cfam/) at the University of Nottingham. I’m having a great time getting to know my new colleagues and learn about their work. And, this week, CfAM and its spin-out company, Added Scientific (https://addedscientific.com/) are hosting a conference here, Additive International (https://www.additiveinternational.com/). So, I feel very fortunate that my orientation weeks have aligned so well the conference. It’s an exceptional opportunity to network with my new colleagues and to get a firm understanding of the current state of the art.

In other news, my latest manuscript, “Influence of moisture and thermal cycling on delamination flaws in transparent armor materials: Thermoplastic polyurethane bonded glass-polycarbonate laminates” was accepted this morning for publication by Materials & Design! It’s the culmination of a two year study performed at the University of Waterloo in my Joint Post-Doc with the Impact Mechanics and Materials Characterizations lab, headed by Dr. Duane Cronin. It’s all about the environmentally-induced failure of simulated transparent armor laminates. Best of all, it’s open-source, so it’s available online, in a pre-publication preliminary state, right here: https://www.sciencedirect.com/science/article/pii/S0264127519304642?via%3Dihub

New Position: University of Nottingham, Centre for Additive Manufacturing

I’m extremely excited to announce that I’ve accepted a job offer at the Centre for Additive Manufacturing at the University of Nottingham. Starting this summer, I’ll be investigating the interaction of surfaces and materials in additive ink jet manufacturing with Dr. Wildman, Dr. Tuck, and their team. Since ink-jetted structures, even those that are mono-material, are conceptually a form of composite if we treat each droplet as its own time-treatment segregated phase, I hope that my experience with multi-scale processes in composites will be invaluable to the Centre and I’m really looking forward to working with such an impressive group of researchers.

New Original Research Article Published

I'm pleased to announce that a new publication of mine has been published.  The work is "Programmable 3D Shape Changes in Liquid Crystal Polymer Networks of Uniaxial Orientation", a great study I co-authored with Dr. Yu Li and Dr. Hamed Shahsavan.  Our article can be found through the following link:   https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201802809 

In this work, the two paths of research in the literature of liquid crystal (LC) and shape memory polymers (SMP) are brought together, resulting in a shape changing polymer that does not need the difficult and costly domain orientation during synthesis that other LC systems require.  Instead, this material can be simple solvent cast in a standard mould, then programmed through thermal and mechanical means to obtain the desired actuation, opening new opportunities for manufacturing complex parts from these exciting materials! 
 

Successful Presentation at ECCM18

On June 26 I was excited to present my talk at the 18th European Conference on Composite Materials, where I discussed my work on "Path-Dependence in Evolution of Electrical Conductivity in Curing Hybrid Nanocomposites: Important Effects Revealed When Studying Silver Nanobelts in a DGEBA/TETA Epoxy Matrix".

I was delighted to receive some excellent questions, and great discussions with the attendees about our unique nanobelt materials and my findings.  I hope the interest in our silver nanobelts I saw in the attendees leads to some excellent work in the future by other groups.   I was also glad to be accompanied by my PhD supervisor, Dr. Pearl Lee-Sullivan, who has provided me with so much excellent guidance through my career.  After my presentation was complete, I was also fortunate to have some wonderful discussions with my colleagues in the composites field about their work.  There was some very impressive composites research on display, and I am grateful to have been a part of it.

Now I'm happy to be home, back in the lab, and putting that new knowledge and perspective to work!

Latest publication now available online

My latest manuscript, "How Interface Compatibility Affects Conductivity Evolution of Silver Nanobelts-filled Electrically Conductive Composites During Cure and Post-Treatments", has just been published by the Journal of Physical Chemistry Chemical Physics, and is now available online!

This work discusses my findings for conductive adhesives and hybrid nanocomposites, focusing on the development of conductivity throughout cure and post-cure treatments.  Our findings include the influences imparted by the particle surfaces, and the path-dependent conductivity development from vitrification during cure.  This may have major impacts on industry procedures and future research, due to the common use by industry of vitrified curing near the gel point of their ECAs.

You can view the article at PCCP's website by following this link, or by following the links in my online CV, posted on my website (geoffreyrivers.com/about).

Latest Manuscript Accepted

My latest manuscript, "How Interface Compatibility Affects Conductivity Evolution of Silver Nanobelts-filled Electrically Conductive Composites During Cure and Post-Treatments", has been accepted for publication by the Journal of Physical Chemistry Chemical Physics! 

This paper explores how the cure procedure, and the resulting polymer dynamics throughout curing, interact with the micro- and nano- scale conductive fillers to produce the final electrical properties.  The findings unveil a number of behaviors not widely reported in the literature, including major deviations in the establishing conductivity, and post-cure conductivity breakdowns that are dependent on the filler content. 

Our investigations found that the difference in surface interactions between the particle types and the polymer matrix are one of the main driving forces of these negative effects, but also provide an opportunity to overcome these disruptive mechanisms.

I will post a link to the manuscript once it is available online.

18th European Conference on Composites Scientific Program Announced

The Scientific Program for ECCM18 in Athens, Greece has been posted.  I will be presenting my work on electrically conductive nanocomposites on Tuesday, June 26, at 3:05 pm in Hall VII.

My talk is entitled "Path-Dependence in Evolution of Electrical Conductivity in Curing Hybrid Nanocomposites: Important Effects Revealed When Studying Silver Nanobelts in a DGEBA/TETA Epoxy Matrix".  I will be presenting our novel findings of the significant influences on the final conductivity of electrically conductive composites from 1) the polymer cure and glass transition behavior and, 2) the interface between the conductive fillers and the matrix.

If you are also attending, feel free to find me and chat. I'd love to answer any questions, and to hear about your research too.

Website for ECCM18: www.ECCM18.org

New opportunities for analyzing polymers and composites with a RheoSpectris

This week my host lab received in a RheoSpectris analyzer from Rheolution Inc.  It's a rheology machine that uses a laser to perform non-contact measurement by looking at resonant frequencies in specimens.  I spent two days receiving hands-on training from company CTO Cédric Schmitt, and I must say I'm quite impressed with the technology.  The software is very easy to use, and the tooling allows for a wide variety of specimen sizes and material property ranges.  We're also excited to start obtaining data all the way up to 2000 Hz, which is far outside the range of our DMA.  I can see this becoming a widely implemented technology very quickly, and I'm excited to be one of the researchers with such early access to it.

My previous experience with this type of analysis is with DMAs and oscillatory rheometers, and there's a few differences that really struck me.  First, the test is very fast for a single temperature. There's also very little calibration required.  The explanation I received is that since the machine is measuring of both the specimen and tooling during operation through the same detection system, the calculations are all done based on the difference and therefore any offset is cancelled out of the math.  Not needing to re-calibrate every time I change the tooling geometry is very exciting.

I'm quite excited to continue using the equipment for testing, and to be responsible for the future training and certification of additional users.

18th European Conference on Composites Announcement

I’m excited to announce that I will be speaking at the 18th  European Conference on Composite Materials, ECCM18, which will be in Athens, Greece, June 24th to 28th!  You can read more about the conference at http://www.eccm18.org/

I’m looking forward to presenting my work, “Path-Dependence in Evolution of Electrical Conductivity in Curing Hybrid Nanocomposites: Important Effects Revealed When Studying Silver Nanobelts in a DGEBA/TETA Epoxy Matrix” (Abstract #805), and meeting many eminent members of my field!

I’ll update here with my timeslot, as scheduling is announced.

Upcoming Changes

I'm currently working on some short videos to present brief abstracts and summaries on papers I've published, complete with links to the publication.  The goal is to provide quick 5 minute introductions to the major findings, and how it relates to the other published works. 

Along with this, I'll be adding "deep dives", where we discuss the underlying mechanisms of our developed materials, such as the synthesis and handling of the silver nanobelts, and some best-practice suggestions for the characterization methods used.