In this context, dielectric polymeric materials are being investigated due to their scientific and technological interest since they combine dielectric properties with appropriate mechanical flexibility and simple processability. [2,3] Such composite materials show huge opportunities to be integrated in devices such as electronics, [4][5][6] sensors and actuators. [7] Within this context, additive manufacturing emerges as a set of advanced fabrication techniques that enable the production of fully functional electronic devices in one step printing. [1,[8][9][10] However, for photopolymerization-based 3D printing techniques the number of UV curable materials suitable for the fabrication of sensors and actuators is still scarce. [1] Research in this field pursues 3D printing materials with new features but also environmentally more friendly and sustainable, as demanded by today's society. [11][12][13] Techniques as stereolithography (SLA) and digital light processing (DLP) are based on the layer-by-layer solidification of a liquid photosensitive resin via UV-light exposure. [14] This is a tailorable process where multicomponent resins provide the photo-rheological and mechanical properties necessary to ensure a successful print. [15] 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 is developed based on a photopolymeric formulation of polyaniline (PANI)/Lignin/acrylate. The amount of photoinitiator and the presence of lignin within the filler are investigated to obtain the best printability and capacitive response. Low PANI contents drastically increase the dielectric constant and 4 wt% photoinitiator improves the signal and sensitivity. A sensitivity of 0.012 kPa -1 is achieved in a linear range (0-10 kPa) with only 3.5 wt% PANI. Lignin improves 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 is selected for the fabrication of a piezocapacitive prototype transducer. The pressure transducer demonstrate 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 electronics.

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.

Several natural matrices were investigated as potential sources of antioxidants to be used as plastic additives. Extracts of four matrices obtained under the same experimental conditions were initially considered: green tea, black tea, Lippia citriodora and Hypericum androsaemum. Both, the antioxidant activity of the extracts and their content in flavanols and quercetin, were compared. The antioxidant activity was determined by DPPH analysis and the phenolic composition by high performance liquid chromatography (HPLC) using ultraviolet (UV) diode array and fluorescence (FL) detectors. Concentration of the flavanols reduced in the same way as their antioxidant activity starting with green tea, through black tea, Hypericum androsaemum, and Lippia citriodora. The performance of polypropylene samples [3553][3554][3555][3556][3557][3558][3559] 2011