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Lima, Nuno, Ana Catarina Baptista, Bruno Morais M. Faustino, Sofia Taborda, Ana Marques, and Isabel Ferreira. "Carbon threads sweat-based supercapacitors for electronic textiles." Scientific Reports 10 (2020): 7703. AbstractWebsite

Flexible and stretchable energy-storage batteries and supercapacitors suitable for wearable electronics are at the forefront of the emerging field of intelligent textiles. In this context, the work here presented reports on the development of a symmetrical wire-based supercapacitor able to use the wearer’s sweat as the electrolyte. The inner and outer electrodes consists of a carbon-based thread functionalized with a conductive polymer (polypyrrole) which improves the electrochemical performances of the supercapacitor. The inner electrode is coated with electrospun cellulose acetate fibres, as the separator, and the outer electrode is twisted around it. The electrochemical performances of carbon-based supercapacitors were analyzed using a simulated sweat solution and displayed a specific capacitance of 2.3 F.g−1, an energy of 386.5 mWh.kg−1 and a power density of 46.4 kW.kg−1. Moreover, cycle stability and bendability studies were performed. Such energy conversion device has exhibited a stable electrochemical performance under mechanical deformation, over than 1000 cycles, which make it attractive for wearable electronics. Finally, four devices were tested by combining two supercapacitors in series with two in parallel demonstrating the ability to power a LED.

Faria, Jaime, Bruno Dionísio, Iris Soares, Ana Catarina Baptista, Ana Cláudia Marques, Lídia Gonçalves, Ana Bettencourt, Carlos Baleizão, and Isabel Ferreira. "Cellulose acetate fibres loaded with daptomycin for metal implant coatings." Carbohydrate polymers (2021): 118733. AbstractWebsite

Multifunctional polymeric coatings containing drug delivery vehicles can play a key role in preventing/reducing biofilm formation on implant surfaces. Their requirements are biocompatibility, good adhesion, and controllable drug release. Although cellulose acetate (CA) films and membranes are widely studied for scaffolding, their applications as a protective coating and drug delivery vehicle for metal implants are scarce. The reason is that adhesion to stainless steel (SS) substrates is non-trivial. Grinding SS substrates enhances the adhesion of dip-coated CA films while the adhesion of electrospun CA membranes is improved by an electrosprayed chitosan intermediate layer. PMMA microcapsules containing daptomycin have been successfully incorporated into CA films and fibres. The released drug concentration of 3 x10-3 mg/mL after 120 minutes was confirmed from the peak luminescence intensity under UV radiation of simulated body fluid (SBF) after immersion of the fibres.

Ropio, Inês, Ana Catarina Baptista, Joana Nobre, J. Correia, F. Belo, S. Taborda, Morais B. M. Faustino, João Borges Borges, A. Kovalenko, and Isabel Ferreira. "Cellulose paper functionalised with polypyrrole and poly(3,4-ethylenedioxythiophene) for paper battery electrodes." Organic Electronics 62 (2018): 530-535. AbstractWebsite

A simple process of commercial paper functionalisation via in situ polymerisation of conductive polymers onto cellulose fibres was investigated and applied as electrodes in paper-based batteries. The functionalisation involved polypyrrole (PPy) and Poly (3,4-ethylenedioxythiophene) (PEDOT) as conductive polymers with the process of functionalisation optimised for each polymer individually with respect to oxidant-to-monomer ratios and polymerisation times and temperature. Paper with conductivity values of 44 mS/cm was obtained by exposing the samples to pyrrole vapour for a period of 30 min at room temperature; however, polymerisation at temperatures of 40 °C lead to higher conductivity values to up 141 mS/cm. Consequently, functionalised PPy and PEDOT papers were applied as cathodes in batteries with Al foil anodes and commercial paper soaked in an electrolyte solution of NaCl.

Baptista, Ana Catarina, Isabel Ferreira, and João Borges. "Cellulose-based bioelectronic devices." In Cellulose - Medical, Pharmaceutical and Electronic Applications, edited by Theo van de Ven and Louis Godbout. InTech, 2013.
Borges, João Paulo, Maria Helena Godinho, Assis Farinha Martins, Ana Catarina Trindade, and Mohamed Naceur Belgacem. "Cellulose-based composite films." Mechanics of composite materials 37 (2001): 257-264. AbstractWebsite

The mechanical and optical properties of cellulose-based composite films are investigated.It is shown that the use of toluene diisocyanate as a coupling agent and Avicel fibers as reinforcing elements give films with the highest mechanical characteristics. Using differential scanning calorimetry, it is also found that the glass transition temperature Tg of all the materials studied is below the room temperature and that the Tg increased with cross-linking and introduction of Avicel.

Baptista, Ana Catarina, Isabel Ferreira, and João Paulo Borges. "Cellulose-based composite systems for biomedical applications." In Biomass based Biocomposites, edited by Vijay Kumar Thakur and A. S. Singha, 47-60. U.K.: Smithers Rapra Technology, 2013.
Baptista, Ana Catarina, Inês Ropio, Beatriz Romba, Joana Nobre, Célia Henriques, Jorge Carvalho Silva, J. I. Martins, João Paulo Borges, and Isabel Ferreira. "Cellulose-based electrospun fibers functionalized with polypyrrole and polyaniline for fully organic batteries." Journal of Materials Chemistry A 6 (2018): 256-265. AbstractWebsite

A novel cellulose-based bio-battery made of electrospun fibers activated by biological fluids has been developed. This work reports a new concept for a fully organic bio-battery that takes advantage of the high surface to volume ratio achieved by an electrospun matrix composed of sub-micrometric fibers that acts simultaneously as the separator and the support of the electrodes. Polymer composites of polypyrrole (PPy) and polyaniline (PANI) with cellulose acetate (CA) electrospun matrix were produced by in situ chemical oxidation of pyrrole and aniline on the CA fibers. The structure (CA/PPy|CA|CA/PANI) generated a power density of 1.7 mW g−1 in the presence of simulated biological fluids, which is a new and significant contribution to the domain of medical batteries and fully organic devices for biomedical applications.

Borges, João Paulo, João Paulo Canejo, Susete Fernandes, Pedro Brogueira, and Maria Helena Godinho. "Cellulose-Based Liquid Crystalline Composite Systems." In Nanocellulose Polymer Nanocomposites: Fundamentals and Applications, edited by Vijay Kumar Thakur, 215-235. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014.
João, Carlos, Jorge Carvalho Silva, and João Paulo Borges. "Chitin-Based Nanocomposites: Biomedical Applications." In Eco-friendly Polymer Nanocomposites, edited by Vijay Kumar Thakur and Manju Kumari Thakur, 439-457. Springer India, 2015. Abstract

Chitin, the second most abundant polymer in nature, is a renewable, nontoxic, biodegradable, and antibacterial polysaccharide. This semicrystalline biopolymer exhibits hierarchical structure from nano to micro-scale and is responsible for interesting living tissue properties. Recently, the scientific interest in chitin nanofibrils for applications in biomedical and tissue engineering fields has increased due to their particular capabilities such as matrix reinforcements, bioactivity and morphology similar to natural tissues. This chapter is focused on composite materials reinforced with chitin nanofibrils and their biomedical applications.

João, Carlos, Ana Teresa Kullberg, Jorge Carvalho Silva, and João Paulo Borges. "Chitosan Inverted Colloidal Crystal scaffolds: Influence of molecular weight on structural stability." Materials Letters 193 (2017): 50-53. AbstractWebsite

Chitosan with three different molecular weights (538 ± 48, 229 ± 45 and 13 ± 3 kDa) was used to develop biodegradable Inverted Colloidal Crystal (ICC) scaffolds with uniform pore size and interconnected pore network. Mass loss and compression modulus were analyzed after hydrolytic degradation in order to understand the influence of molecular weight on structural and mechanical degradation of chitosan ICC structures. Results show that medium molecular weight chitosan (229 ± 45 kDa) retains ICC structure and compression modulus for an extended period (4 weeks) and is therefore the preferred one for the production of ICC for soft tissue engineering.

Soares, Paula I. P., Ana Isabel Sousa, Jorge Carvalho Silva, Isabel Ferreira, Carlos Novo, and João Paulo Borges. "Chitosan-based nanoparticles as drug delivery systems for doxorubicin: optimization and modelling." Carbohydrate polymers 147 (2016): 304-312. AbstractWebsite

In the present work, two drug delivery systems were produced by encapsulating doxorubicin into chitosan and O-HTCC (ammonium-quaternary derivative of chitosan) nanoparticles. The results show that doxorubicin release is independent of the molecular weight and is higher at acidic pH (4.5) than at physiological pH. NPs with an average hydrodynamic diameter bellow 200 nm are able to encapsulate up to 70% and 50% of doxorubicin in the case of chitosan and O-HTCC nanoparticles, respectively. O-HTCC nanoparticles led to a higher amount of doxorubicin released than chitosan nanoparticles, for the same experimental conditions, although the release mechanism was not altered. A burst effect occurs within the first hours of release, reaching a plateau after 24 h. Fitting mathematical models to the experimental data led to a concordant release mechanism between most samples, indicating an anomalous or mixed release, which is in agreement with the swelling behavior of chitosan described in the literature.

Zamora-Mora, Vanessa, Paula I. P. Soares, Coro Echeverria, Rebeca Hernández, and Carmen Mijangos. "Composite chitosan/agarose ferrogels for potential applications in magnetic hyperthermia." Gels 1 (2015): 69-80. AbstractWebsite

Composite ferrogels were obtained by encapsulation of magnetic nanoparticles at two different concentrations (2.0 and 5.0 % w/v) within mixed agarose/chitosan hydrogels having different concentrations of agarose (1.0, 1.5 and 2.0% (w/v)) and a fixed concentration of chitosan (0.5% (w/v)). The morphological characterization carried out by scanning electron microscopy showed that dried composite ferrogels present pore sizes in the micrometer range. Thermogravimetric measurements showed that ferrogels present higher degradation temperatures than blank chitosan/agarose hydrogels without magnetic nanoparticles. In addition, measurements of the elastic moduli of the composite ferrogels evidenced that the presence of magnetic nanoparticles in the starting aqueous solutions prevents to some extent the agarose gelation achieved by simply cooling chitosan/agarose aqueous solutions. Finally, it is shown that composite chitosan/agarose ferrogels are able to heat in response to the application of an alternating magnetic field so that they can be considered as potential biomaterials to be employed in magnetic hyperthermia treatments.

Perdigão, Patrícia, Bruno Faustino, Jaime Faria, João Paulo Canejo, João Borges Borges, Isabel Ferreira, and Ana Catarina Baptista. "Conductive Electrospun Polyaniline/Polyvinylpyrrolidone Nanofibers: Electrical and Morphological Characterization of New Yarns for Electronic Textiles." Fibers 8 (2020): 24. AbstractWebsite

Advanced functionalities textiles embedding electronic fibers, yarns and fabrics are a demand for innovative smart cloths. Conductive electrospun membranes and yarns based on polyaniline/polyvinylpyrrolidone (PANI/PVP) were investigated using the chemical modification of PANI instead of using conventional coating processes as in-situ polymerization. PANI was synthesized from the aniline monomer and the influence of the oxidant-to-monomer ratio on electrical conductivity was studied. The optimized conductivity of pellets made with pressed PANI powders was 21 S·cm−1. Yarns were then prepared from the t-Boc-PANI/PVP electrospun membranes followed by PANI protonation to enhance their electrical properties. Using this methodology, electrospun membranes and yarns were produced with electrical conductivities of 1.7 × 10−2 and 4.1 × 10−4 S·cm−1.

Marques, Susana, Paula I. P. Soares, Coro Echeverria, Maria Helena Godinho, and João Paulo Borges. "Confinement of thermoresponsive microgels into fibres via colloidal electrospinning: experimental and statistical analysis." RSC Advances 6 (2016): 76370-76380. AbstractWebsite

The strategy of confining stimuli-responsive microgels in electrospun fibres would allow the fabrication of polymeric networks that combine the microgels swelling ability and properties with the interest features of the electrospun fibres. Colloidal electrospinning is an emerging method in which fibres containing microgels can be produced by a single-nozzle and designed through the solution carrier materials. The incorporation of poly(N-isopropylacrylamide) (PNIPAAM) and PNIPAAM-chitosan (PNIPAAM-CS) in poly(ethyleneoxyde) (PEO) fibres via colloidal electrospinning producing composite fibres was the main purpose of the present work{,} which was confirmed by means of Scanning Electron Microscopy (SEM). Dynamic light scattering was used to analyse the microgels hydrodynamic diameter ranging up to 900 nm depending on the composition and temperature of the surrounding medium. By performing a statistical analysis the relationship of the processing variables over the fibre size was evaluated following the response surface methodology (RSM). From the set of parameters aimed to minimize the fibre diameter{,} composite fibres with an average diameter of 63 nm were produced. Only the as-prepared microgels with higher monodispersity provided {"}bead-on-a-string{"} morphologies.

Cristovão, Ana Filipa, David Sousa, Filipe Silvestre, Inês Ropio, Ana Gaspar, Célia Henriques, Alexandre Velhinho, Ana Catarina Baptista, Miguel Faustino, and Isabel Ferreira. "Customized tracheal design using 3D printing of a polymer hydrogel: influence of UV laser cross-linking on mechanical properties." 3D Printing in Medicine 5 (2019): 12. AbstractWebsite

Background
The use of 3D printing of hydrogels as a cell support in bio-printing of cartilage, organs and tissue has attracted much research interest. For cartilage applications, hydrogels as soft materials must show some degree of rigidity, which can be achieved by photo- or chemical polymerization. In this work, we combined chemical and UV laser polymeric cross-linkage to control the mechanical properties of 3D printed hydrogel blends. Since there are few studies on UV laser cross-linking combined with 3D printing of hydrogels, the work here reported offered many challenges.

Methods
Polyethylene glycol diacrylate (PEGDA), sodium alginate (SA) and calcium sulphate (CaSO4) polymer paste containing riboflavin (vitamin B2) and triethanolamine (TEOHA) as a biocompatible photoinitiator was printed in an extrusion 3D plotter using a coupled UV laser. The influence of the laser power on the mechanical properties of the printed samples was then examined in unconfined compression stress-strain tests of 1 × 1 × 1 cm3 sized samples. To evaluate the adhesion of the material between printed layers, compression measurements were performed along the parallel and perpendicular directions to the printing lines.

Results
At a laser density of 70 mW/cm2, Young’s modulus was approximately 6 MPa up to a maximum compression of 20% in the elastic regime for both the parallel and perpendicular measurements. These values were within the range of biological cartilage values. Cytotoxicity tests performed with Vero cells confirmed the cytocompatibility.

Conclusions
We printed a partial tracheal model using optimized printing conditions and proved that the materials and methods developed may be useful for printing of organ models to support surgery or even to produce customized tracheal implants, after further optimization.