Printability Study of a Conductive Polyaniline/Acrylic Formulation for 3D Printing

[Abstract] There is need for developing novel conductive polymers for Digital Light Processing (DLP) 3D printing. In this work, photorheology, in combination with Jacobs working curves, efficaciously predict the printability of polyaniline (PANI)/acrylate formulations with different contents of PANI and photoinitiator. The adjustment of the layer thickness according to cure depth values (Cd) allows printing of most formulations, except those with the highest gel point times determined by photorheology. In the working conditions, the maximum amount of PANI embedded within the resin was ≃3 wt% with a conductivity of 10−5 S cm−1, three orders of magnitude higher than the pure resin. Higher PANI loadings hinder printing quality without improving electrical conductivity. The optimal photoinitiator concentration was found between 6 and 7 wt%. The mechanical properties of the acrylic matrix are maintained in the composites, confirming the viability of these simple, low-cost, conductive composites for applications in flexible electronic devices.Xunta de Galicia; ED481A-2019/001Xunta de Galicia; ED431C 2019/17Goretti Arias-Ferreiro thanks the financial funding received from the Xunta de Galicia and the European Union (Program to support the predoctoral stage at SUG 2019 (ED481A-2019/001)). The authors would like to thank the financial support from Xunta de Galicia-FEDER (Program of Consolidation and structuring competitive research units (ED431C 2019/17))

Multivariate Analysis of Tronchuda Cabbage (Brassica oleracea L. var. costata DC) Phenolics: Influence of Fertilizers

9 pages, 5 figures, 2 tables.A field experiment was carried out to investigate the effect of fertilization level on the phenolic composition of tronchuda cabbage (Brassica oleracea L. var. costata DC) external and internal leaves. Eight different plots were constituted: a control without fertilization, one with organic matter, and six experiments with conventional fertilizers (nitrogen, boron, and sulfur, two levels each). The phenolic compounds were analyzed by reversed-phase HPLC-DAD. External and internal leaves revealed distinct qualitative composition. In the internal leaves were found 15 phenolics (5 kaempferol and 10 cinnamic acid derivatives), whereas the external leaves presented 3-p-coumaroylquinic acid and 13 kaempferol derivatives. Principal component analysis (PCA) was applied to assess the relationships between phenolic compounds, agronomical practices, and harvesting time. Samples obtained with conventional practices were quite effectively separated from organic samples, for both types of leaves. In general, samples developed without any fertilization presented the highest phenolics amounts: external and internal leaves contained 1.4- and 4.6-fold more phenolic compounds than the ones that received conventional fertilizer, respectively, and the internal leaves presented 2.4 times more phenolics than the ones grown with organic amendment. Additionally, samples from organic production exhibited higher total phenolics content than those from conventional practices, collected at the same time. Samples harvested first were revealed to be distinct from the ones collected later. The results show that it is possible to grow tronchuda cabbage without excess fertilizers, with highest amounts of phenolics and reduced environment contamination.We are grateful to Fundação para a Ciência e Tecnologia (FCT) for financial support of this work (POCI/AGR/57399/2004). M.S.D.-G. is indebted to FCT for her grant (SFRH/BPD/21757/2005).Peer reviewe

Photocurable printed piezocapacitive pressure sensor based on an acrylic resin modified with polyaniline and lignin

The design of suitable materials for the manufacture of pressure sensors with high sensitivity and flexibility in wearable electronics is still a challenge. In this study, a flexible and portable pressure sensor has been developed based on a photopolymeric formulation of polyaniline (PANI) /Lignin/acrylate. The amount of photoinitiator and the presence of lignin within the filler were investigated in order to obtain the best printability and capacitive response. Low PANI contents drastically increased the dielectric constant and 4 wt.% photoinitiator improved the signal and sensitivity. A sensitivity of 0.012 kPa-1 was achieved in a linear range (0 to 10 kPa) with only 3.5 wt.% PANI. Lignin improved both the dispersion of the filler within the matrix and the printability of the resin, due to lower absorptivity at the UV wavelength of the 3D printer. Thus, the PANI-Lignin filler was selected for the fabrication of a piezocapacitive prototype transducer. The pressure transducer demonstrated its practical application by responding to a human footfall and transmitting its corresponding electrical signal. This study shows the enhanced properties of lignin modified PANI acrylate composites. Based on lignin, an abundant natural waste, a sustainable photocurable cost-effective polymer is proposed for the fabrication of printable, wearable electronicsG.A.-F. would like to thank the financial funding received from the Xunta de Galicia and the European Union (Program to support the predoctoral stage at SUG 2019 (ED481A-2019/001)) and the Iacobus program (Candidature n degrees 35, 2020/2021 edition). The authors would like to thank the financial support from Ministerio de Ciencia e Innovacion/FEDER (project ref; PID2020-116976RB-I00) and Xunta de Galicia-FEDER (Program of Consolidation and structuring competitive research units (ED431C 2019/17 and ED431B 2019/44)). Furthermore, the authors thank FCT - Portuguese Foundation for Science and Technology for funding under Strategic Funding UIDB/00319/2021 and grant SFRH/BPD/110914/2015 (P.C.). Financial support from the Basque Government Industry under the ELKARTEK program is also acknowledged. Funding for open access charge: Universidade da Coruna/CISUG

Flexible 3D printed acrylic composites based on polyaniline/multiwalled carbon nanotubes for piezoresistive pressure sensors

The development of tunable UV-curable polymeric composites for functional applications, taking into consideration environmental issues and additive manufacturing technologies, is a research topic with relevant challenges yet to be solved. Herein, acrylic composites filled with 0–3 wt.%. polyaniline/ multiwalled carbon nanotubes (PANI/MWCNT) are prepared by Digital Light Processing (DLP) in order to tailor morphology, thermal, mechanical, and electromechanical properties. Viscosity, real-time infrared spectroscopy, and cure depth tests allow optimizing resin composition for suitable DLP printing. 2 wt.% is the maximum filler content reproducibly embedded in the polymer matrix. The advantages of PANI/MWCNT (50/50 wt.%) compared with single-component composites include safety issues, enhanced printability, increased electrical conductivity and thermal stability, and lower electrical percolation threshold (0.83 wt.%). Above this threshold the composites display excellent piezoresistive response, no hysteresis, and stability for over 400 compression cycles. The pressure sensibility (PS) of 2 wt.% composites decreases with applied pressure from PS ≈ 15 to 0.8 Mpa−1 for maximum pressures of 0.02 and 0.57 MPa, respectively. A proof-of-concept of the functionality of the novel materials is developed in the form of a tactile sensor, demonstrating their potential for pressure sensing applications as cost-effective, sustainable, and flexible materials for printed electronics.Goretti Arias-Ferreiro would like to thank the financial funding received from the Xunta de Galicia and the European Union (ED481A-2019/001). The authors would like to thank the financial support from Ministerio de Ciencia e Innovacion/FEDER (reLiCom3D project ref PID2020-116976RB-I00) and Xunta de GaliciaFEDER (ED431C 2019/17). Furthermore, the authors thank FCT - Portuguese Foundation for Science and Technology for funding under Strategic Funding UIDB/00319/2021 and grant SFRH/BPD/110914/2015 (P.C.). Financial support from the Basque Government Industry under the ELKARTEK program is also acknowledged. Funding for open access charge: Universidade da Coruña/CISUG