Research

Transparent wood is a sustainable and innovative material with promising applications in energy-efficient construction, optical devices and design. The preparation process involves two key steps. First, lignin (the main light-absorbing component in wood) is removed while preserving the cellular structure. Second, the structure is infiltrated with materials whose refractive index closely matches that of cellulose to reduce light scattering. We are investigating both biopolymer solutions and in situ polymerizing monomers. However, the in situ polymerization approach offers better performance due to their lower viscosity and greater ability to uniformly fill the wood’s internal structure, resulting in improved transparency.

It is critical to monitor the structural evolution of complex fluids for optimal manufacturing performance, including textile spinning. However, in situ measurements in a textile-spinning process suffer from the paucity of non-destructive instruments and interpretations of the measured data. This system enables to capture key geometrical and structural information of the fiber under spinning, including the flow kinematics extracted from feature tracking, and the flow-induced morphology and birefringent responses. The birefringent responses of fibers under coagulation are compared with an orientation factor incorporated in the constitutive rheological model, from which a superposed structure-optic relationship under varying spinning conditions is identified.

Aiming to increase the scarce information available on the kinetics of cellulose dissolution, we have applied an image-assisted technique based on the luminance evolution as cellulose dissolves to study this process under different experimental conditions. This protocol was validated via direct determination of the cellulose dissolved. In all cases datapoints were linearly fitted assuming a pseudo-zero order reaction which facilitates the comparison between datasets.

Silk-based films with pH sensors can be obtained by covalently grafting a neutral red dye onto silk fibroin through a Mannich reaction. These halochromic films, manufactured from regenerated fibroin, respond with high sensitivity, reversibility, and reusability to pH variations over a wide range. Color changes are monitored by spectrophotometry and image analysis with smartphones, enabling accessible and accurate detection. These sensors can also detect volatile ammonia, making them suitable for monitoring the freshness of seafood products. The objective of this initiative is to develop sensors that are both sustainable and biodegradable, with applications in real-time environmental, biomedical, and food safety monitoring.

Conventional synthetic packaging materials, predominantly non-biodegradable polymers, fail to effectively address food spoilage while contributing to environmental pollution. To overcome these limitations, active packaging materials have emerged as a promising strategy for extending shelf life and maintaining the quality of consumables. Electrospinning, a cost-effective and versatile technique for producing nonwoven polymer fibers, in the micro-to-nanometric range, enables the incorporation of functional agents such as lignin nanoparticles, known for their antioxidant, antimicrobial, and UV-blocking properties. By utilizing a self-developed three-dimensional electrospinning system, highly uniform polyvinyl alcohol mats with homogeneously dispersed lignin nanoparticles were fabricated, enhancing the potential of electrospun bio-based materials to reduce food spoilage, offering a viable alternative to conventional packaging.

Aiming to increase the scarce information available on the kinetics of cellulose dissolution, we have applied an image-assisted technique based on the luminance evolution as cellulose dissolves to study this process under different experimental conditions. This protocol was validated via direct determination of the cellulose dissolved. In all cases datapoints were linearly fitted assuming a pseudo-zero order reaction which facilitates the comparison between datasets.

Lignin is a natural biopolymer found in the cell walls of plants. Kraft lignin, in particular, is a widely available by-product of the paper industry, to which we aim to add value due to its potential as a renewable resource. In this research line, we produce Kraft lignin nanoparticles using the antisolvent method and incorporate them into biodegradable polyvinyl alcohol (PVA) films. The goal is to enhance antioxidant activity, UV absorption, and hydrophobicity, creating functional materials for active packaging and industrial applications.

Separation technologies are key for the chemical processing of the massive amount of polycotton waste generated worldwide. The distinct chemical nature of cellulose and polyethylene terephthalate (PET) guides the design of fractionation strategies to obtain two valuable monomaterial streams. The optimal fractionation process is, in our view, highly context dependent what conveys to seek a variety of alternatives seeking for chemical processes driven by the ulterior up-cycling of the monomaterial streams. On the PET side, alkaline depolymerization yields monomers for the synthesis of recycled polyester, while cellulose remains as fiber-grade feedstock. Alternatively, we investigate pathways that chemically transform the cellulose fraction into spinnable mixtures or fermentable sugars for further valorisation. This research supports the development of chemical routes for the recycling of mixed textile waste.

A successful initial setup was built using a syringe pump, positioned above a water bath, which served as the propulsion system for the cellulose solution. While the extrusion capacity of the pump covers a broad range of linear forces, these values were proved insufficient for processing high concentrations of cellulose. To address this limitation, a new propulsion system was designed and fabricated. This updated setup features a stepper motor driving a piston within a stainless-steel body, generating a constant material flow through the nozzle. It also supports the use of commercial single-hole nozzles with various diameters. With this enhancement, the system is now capable of extruding highly concentrated polymeric solutions under mild conditions.