Browsing by Author "Abitbol, Tiffany"

Filter results by typing the first few letters
Now showing 1 - 4 of 4
  • Design of experiments to investigate multi-additive cellulose nanocrystal films
    (2022-11-04) Nilsson, Patrik; Engström, Åsa; Kaschuk, Joice Jaqueline; Vapaavuori, Jaana; Larsson, Arvid; Abitbol, Tiffany
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose nanocrystal (CNC) suspensions can self-assemble into chiral nematic films upon the slow evaporation of water. These films are brittle, as indicated by their fracturing instead of plastically deforming once they are fully elastically deformed. This aspect can be mediated to some extent by plasticizing additives, such as glucose and glycerol, however, few reports consider more than one additive at a time or address the influence of additive content on the homogeneity of the self-assembled structure. In this work, design of experiments (DoE) was used to empirically model complex film compositions, attempting to relate additive concentrations in dilute suspension to film properties, and to understand whether outcome specific predictions are possible using this approach. We demonstrate that DoE can be used to predict film properties in multi-additive systems, without consideration given to the different phenomena that occur along the drying process or to the nature of the additives. Additionally, a homogeneity metric is introduced in relation to chiral nematic organization in CNC films, with most of the additive-containing compositions in this work found to reduce the homogeneity of the self-assembly relative to pure CNC films.
  • A facile spinning approach towards the continuous production of aligned nanocellulose films
    (2024-11-20) Daghigh Shirazi, Hamidreza; Håkansson, Karl M.O.; Abitbol, Tiffany; Vapaavuori, Jaana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this work, we present an alternative approach to cellulose nanofibril film (CNF) production, taking inspiration from the wet spinning of fibers to wet spin films. During the spinning process, a CNF suspension is injected into a coagulation bath, where the partially aligned CNF network is locked. The CNF alignment of the dry films is then detected by wide angle X-ray scattering (WAXS). The comparison between the ultimate strengths and strengths at breaks of the films produced with different process parameters, including the suspension injection rate, bath pH, and bath flow rate, indicated no significant change in mechanical properties, suggesting a reliable and constant outcome for large-scale film fabrication. Furthermore, the produced films demonstrated high total light transmittance of 93 % at the wavelength of 550 nm, making them suitable for optoelectronic applications. Polarized optical microscopy revealed that even a low degree of CNF alignment can lead to anisotropic optical properties. Moreover, an anisotropic response to humidity was observed, in which the films preferentially bend in the perpendicular direction of the CNF orientation, thus opening a way for humidity-driven actuators.
  • Plant-Based Structures as an Opportunity to Engineer Optical Functions in Next-Generation Light Management
    (2022-02-10) Kaschuk, Joice Jaqueline; Al Haj, Yazan; Rojas, Orlando J.; Miettunen, Kati; Abitbol, Tiffany; Vapaavuori, Jaana
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    This review addresses the reconstruction of structural plant components (cellulose, lignin, and hemicelluloses) into materials displaying advanced optical properties. The strategies to isolate the main building blocks are discussed, and the effects of fibrillation, fibril alignment, densification, self-assembly, surface-patterning, and compositing are presented considering their role in engineering optical performance. Then, key elements that enable lignocellulosic to be translated into materials that present optical functionality, such as transparency, haze, reflectance, UV-blocking, luminescence, and structural colors, are described. Mapping the optical landscape that is accessible from lignocellulosics is shown as an essential step toward their utilization in smart devices. Advanced materials built from sustainable resources, including those obtained from industrial or agricultural side streams, demonstrate enormous promise in optoelectronics due to their potentially lower cost, while meeting or even exceeding current demands in performance. The requirements are summarized for the production and application of plant-based optically functional materials in different smart material applications and the review is concluded with a perspective about this active field of knowledge.
  • Processing factors affecting roughness, optical and mechanical properties of nanocellulose films for optoelectronics
    (2024-05-15) Kaschuk, Joice Jaqueline; Al Haj, Yazan; Valdez Garcia, Joaquin; Kamppinen, Aleksi; Rojas, Orlando J.; Abitbol, Tiffany; Miettunen, Kati; Vapaavuori, Jaana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This work aims to understand how nanocellulose (NC) processing can modify the key characteristics of NC films to align with the main requirements for high-performance optoelectronics. The performance of these devices relies heavily on the light transmittance of the substrate, which serves as a mechanical support and optimizes light interactions with the photoactive component. Critical variables that determine the optical and mechanical properties of the films include the morphology of cellulose nanofibrils (CNF), as well as the concentration and turbidity of the respective aqueous suspensions. This study demonstrates that achieving high transparency was possible by reducing the grammage and adjusting the drying temperature through hot pressing. Furthermore, the use of modified CNF, specifically carboxylated CNF, resulted in more transparent films due to a higher nanosized fraction and lower turbidity. The mechanical properties of the films depended on their structure, homogeneity (spatial uniformity of local grammage), and electrokinetic factors, such as the presence of electrostatic charges on CNF. Additionally, we investigated the angle-dependent transmittance of the CNF films, since solar devices usually operate under indirect light. This work demonstrates the importance of a systematic approach to the optimization of cellulose films, providing valuable insight into the optoelectronic field.