During a meeting, conference, workshop, or coffee break, a brilliant idea sometimes shines in the restless mind of a PhD student. Looking into it and trying to formulate a good plan to work on it, the student realizes that some aspects are way outside of her field of knowledge… and there is not enough time to become an expert in all scientific fields. This realization will undeniably lead the student to ask for help and hopefully, a collaboration will begin. As with any experiment, a collaboration can be fruitful and lead to high-value results which add to our understanding of the world. If things are not managed well however, an attempted collaboration can mean the end of a professional relationship, or even the abandonment of a project altogether. It’s all a matter of communication! Being clear about the expectations on everyone involved is a key ingredient of a successful collaboration. This has been an important lesson for me to learn at the beginning of my career, as I have had the opportunity to bring collaborators into my own projects and also had the chance to contribute to others’ work.
There are different degrees of involvement in a collaborative project. A seemingly simple or “small” contribution for me could be performing a short series of characterizations and the corresponding analyses. Such a seemingly small experiment, which might be quite easy for the person doing it, can generate data that are pivotal to a certain publication, yet contributions like this often go unrecognised. This leads to ethical issues such as people not being given credit for their work. It is a very fulfilling experience to have your intellectual work recognised as an actual contribution to a study, and the guidelines of the International Committee of Medical Journal Editors are very helpful in defining who should be listed as an author. I am happy and honoured to have recently been included in publications deriving from three interesting projects in which I performed lignin characterization by using nuclear magnetic resonance experiments and size exclusion chromatography. These are methods I am familiar with, but they take time and expertise to both perform and interpret.
In the first collaboration, published in the journal Cellulose (Ghaffari et al., Cellulose, 2023, 30, 3685–3698,doi.org/10.1007/s10570-023-05098-8), lignin diffusion through a cellulosic membrane was explored. A diffusion cell was used as a model to study what happens during delignification of pulp. The success of this process depends on the effective diffusion of lignin through a cellulosic matrix, and this project aimed to understand the parameters that govern and can affect that process. The diffusion cell used in this study was equipped with a cellulosic membrane, and lignin solutions were provided on one side of the cell membrane. The impacts of lignin alkalinity and size were investigated by varying the pH of lignin solutions and the molecular weight of the lignin fraction used.
By performing a series of characterizations of the chemical properties of lignin in the donor and acceptor solutions, i.e. the solutions on each side of the cellulosic membrane, we could conclude that low molecular weight of lignin and high pH of the solution can increase diffusivity. This was attributed both to changes in the conformation of the polymeric structure of lignin and in the membrane itself. For example, high pH is known to reduce self-association of lignin, making it easier to diffuse through smaller pore size. We also found that alkalinity increases the porosity of the membrane, by swelling of cellulose. The results of this study can be used in the optimization of pulping to improve the yield and efficiency of the processes.
Next, two publications showcase the amazing properties of wood aerogels. The paper published in Advanced Functional Materials (Garemark et al. Advanced Functional Materials, 2023, 33 (4), 2208933, doi.org/10.1002/adfm.202208933) described the formation of a wood aerogel that can to be used as a power generator, by harvesting the hydrovoltaic energy produced during water evaporation. Wood samples were treated with sodium hydroxide at -6 °C, which led to the partial dissolution of the polymeric components of wood that diffuse to the empty lumen. Then, the dissolved polymers precipitated with the addition of water and formed a network of fibrils in the lumen. This re-distribution of the wood structure offers several advantages to this application. For example, the surface area of the material is increased, so there is an increased evaporation at the water-air interface. In a very cool demonstration of this technology, these wood power generators were connected in series and used to power a digital timer (https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202208933, see Supplemental Video 1).
The second application we demonstrated, published in ACS Nano (Garemark et al. ACS Nano, 2023, 17, 5, 4775–4789, doi.org/10.1021/acsnano.2c11220), was of a shape-memory wood aerogel. Polymeric shape-memory aerogels can be used in a variety of applications as insulators, actuators, or sensors. Currently they are mostly made of fossil-based materials and produced via complicated methodologies. As a result, this new wood-based application opens the way to sustainable development in this field. The wood aerogels are prepared by a one-pot treatment of wood samples with an ionic liquid and dimethylsulfoxide. There is a partial solubilization and redistribution of the wood components, as in the previous material. Upon the addition of water that leads to their precipitation, a fibrillar network is formed inside the lumen. Importantly, lignin is not severely modified during this process, and only a small degree of bond cleaving was observed, showing that ‘native’ or unmodified lignin has real technological applicability. The still-high lignin content in the aerogel, and the redistribution of the polymeric materials after solubilization and precipitation, is thought to be the cause of the excellent mechanical properties of the aerogel, which are in the same range as wood itself.
Participating in the above projects was an exciting experience as I was given the opportunity to discuss the relation of my own more “theoretical” lignin research in the context of specific material applications. My PhD thesis will discuss the importance of advanced knowledge of the native lignin structure, and how that can help design sustainable lignin-related processes and materials, and these works are important demonstrators of that concept. It is always nice to discuss with enthusiastic colleagues about cool projects and share your passion about your own research field. It is also a great accomplishment to use the skills that have been gained during your studies to contribute to others’ work, so I encourage all PhD students to talk to their supervisors about the potential for collaborative participation. I am looking forward to more collaborations like these.
Stockholm CAZyme Lab 