Mid Sweden University

The rising demand for wireless electronics and sustainable energy solutions drives the search for alternatives to conventional batteries. Triboelectric nanogenerators (TENGs) offer a promising route by converting mechanical energy into electricity via frictional events between two different material surfaces. Here, a simple and scalable surface modification method using conventional laser printing was applied to investigate the effect on triboelectric performance of cellulose-based materials against polytetrafluoroethylene (PTFE). Regenerated cellulose (RC) and cellulose acetate (CA) films were print patterned with black toner in a conventional laser printer at different surface coverages from 0% to 100%. The measured power output for RC films against PTFE showed minimal response from the patterning over the whole range and could be considered as constant with an average of 52 ± 2 W m−2. On the other hand, the CA sample films showed a significant and gradual increase in power output from 45 to 65 W m−2 as the toner print coverage increased from 0% to 100%. These results demonstrate that synergistic interactions between the printed toner and the substrate can strongly influence TENG performance and are highly dependent on the physical and chemical properties of the underlying material. In CA, toner–substrate intermixing enabled by laser printing temperatures exceeding the glass transition temperature provides a proof-of-concept for enhancing triboelectric performance through controlled surface–bulk interactions. 

Four new compositionally complex perovskites with multiple (four or more) cations on the B site of the perovskites have been studied. The materials have the general formula La0.5Sr2.5(M)2O7−δ (M = Ti, Mn, Fe, Co, and Ni) and have been synthesized via conventional solid-state synthesis. The compounds are the first reported examples of compositionally complex n = 2 Ruddlesden-Popper perovskites. The structure and properties of the materials have been determined using powder X-ray diffraction, neutron diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and magnetometry. The materials are isostructural and adopt the archetypal I4/mmm space group with the following unit cell parameters: a ∼ 3.84 Å, and c ∼ 20.1 Å. The measured compositions from energy dispersive X-ray spectroscopy were La0.51(2)Sr2.57(7)Ti0.41(2)Mn0.41(2)Fe0.39(2)Co0.38(1)Ni0.34(1)O7−δ, La0.59(4)Sr2.29(23)Mn0.58(5)Fe0.56(6)Co0.55(6)Ni0.42(4)O7−δ, La0.54(2)Sr2.49(13)Mn0.41(2)Fe0.81(5)Co0.39(3)Ni0.36(3)O7−δ, and La0.53(4)Sr2.55(19)Mn0.67(6)Fe0.64(5)Co0.31(2)Ni0.30(3)O7−δ. No magnetic contribution is observed in the neutron diffraction data, and magnetometry indicates a spin glass transition at low temperatures. 

Temperature-dependent dc-magnetization and ac-susceptibility curves have been recorded for series of single and double layered Ruddlesden-Popper multicomponent perovskites with chemical formula A2BO4 and A3B2O7, respectively, with (La, Sr) on A-sites and up to 7 different cations on the B-sites (Ti, Cr, Mn, Fe, Co, Ni, Cu). The phase purity and chemical homogeneity of the compounds were investigated by X-ray diffraction and energy dispersive X-ray spectroscopy. Independently of the composition, spin glassiness is observed in both systems. Scaling analyses suggest the materials undergo spin glass phase transitions at low temperatures. Yet, qualitative differences are observed between the single-layered and double-layered systems, which are discussed in the light of the spatial dimensionality and magnetic interaction in layered oxide perovskites.

Triboelectric nanogenerators (TENGs) are ideal to meet the increasing need for green and efficient energy solutions, e.g., in small wireless and/or wearable applications. Regenerated cellulose is an exemplary material regarding both power output and mechanical performance, and it is environmentally friendly and economically favourable. To further improve the triboelectric performance of the cellulose, colour printing was done on the surface with conventional laser printing. Printer toners commonly contain substances with different triboelectric properties. [1] In this work, cellulose fibres were dissolved using a LiOH/urea solvent and regenerated in an ethanol bath and eventually dried under controlled conditions. Thereafter the resulting transparent cellulose films were run through a conventional laser paper printer to apply toners of different colour and patterns on the surface. Cyan, magenta, yellow and black was printed in one layer. In addition, black was printed in certain patterns from low to high coverage and in several layers to evaluate the effect of applied amount. The samples were analysed using SEM, AFM, XRD, FTIR and a TENG was assembled in the contact-separation mode to investigate the triboelectric performance. The printed cellulose films were found to give enhanced triboelectric output. The results show an interesting and simple processing route to enhance the performance of cellulose- based TENG materials that can be useful in the development of cheap and sustainable small wireless electrical generators or sensors.

[1] Zhang, R.; Hummelgård, M.; Örtegren, J.; Andersson, H.; Olsen, M.; Chen, W.; Wang, P.; Eivazi, A.; Dahlström, C.; Norgren, M., Adv. Engin. Mater., 2023, in press, https://doi.org/10.1002/adem.202300107