Publications

We report the fabrication and characterization of a highly sensitive pressure sensor that has been successfully tested using 3D-bioprinted skeletal muscle tissue. The proposed pressure sensor consists of two assembled 3D printed specimens, which were obtained using 60/40 v/v poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) / poly(ethylene glycol) diacrylate (PEGDA) mixture, placed between two indium tin oxidecoated polyethylene terephthalate (PET-ITO) films. The printed specimens were shaped with a serrated structure, improving the sensitivity of the contact when pressed against PET-ITO film. Initially, the performance of the fabricated pressure sensor was tested using light cylindrical weights, which corresponded to pressures ranging from 0.99 to 14.71 kPa, and as prove of concept, carefully pressing with the finger (from 2.91 to 6.81 kPa). As the sensitivity and fast response of sensor were compatible with detection of soft muscle contractions, 3D-bioprinted skeletal muscle bioactuators were manufactured using myoblast cells. The contractions of the bioactuators, which were induced using electrical stimulation, exerted a pressure of 1.5 kPa only that was clearly and precisely detected by the sensor. Overall, the potential application of proposed pressure sensor for wearable and biomedical devices is evidenced by demonstrating its fast response time (< 50 ms) and sensitivity.

JTD Keywords: 4-ethylenedioxythiophene), Bioactuator, Healt, Hydrogels, Poly(3, Poly(ethylene glycol) diacrylate, Raman-spectroscopy, Soft electronics, Wearable electronic

Many studies have focused on novel noninvasive techniques to monitor respiratory rate such as bioimpedance. We propose an algorithm to detect respiratory phases using wearable bioimpedance to compute time parameters like respiratory rate, inspiratory and expiratory times, and duty cycle. The proposed algorithm was compared with two other algorithms from literature designed to estimate the respiratory rate using physiological signals like bioimpedance. We acquired bioimpedance and airflow from 50 chronic obstructive pulmonary disease (COPD) patients during an inspiratory loading protocol. We compared performance of the algorithms by computing accuracy and mean average percentage error (MAPE) between the bioimpedance parameters and the reference parameters from airflow. We found similar performance for the three algorithms in terms of accuracy (>0.96) and respiratory time and rate errors (<3.42 %). However, the proposed algorithm showed lower MAPE in duty cycle (10.18 %), inspiratory time (10.65 %) and expiratory time (8.61 %). Furthermore, only the proposed algorithm kept the statistical differences in duty cycle between COPD severity levels that were observed using airflow. Accordingly, we suggest bioimpedance to monitor breathing pattern parameters in home situations.Clinical relevance - This study exhibits the suitability of wearable thoracic bioimpedance to detect respiratory phases and to compute accurate breathing pattern parameters. © 2021 IEEE.

JTD Keywords: algorithms, copd, signals, Algorithm, Algorithms, Bioimpedance, Breathing rate, Chronic obstructive lung disease, Electronic device, Human, Humans, Lung, Pulmonary disease, chronic obstructive, Respiratory rate, Wearable electronic devices

The utilization of hydrogels derived from biopolymers as solid electrolyte (SE) of electrochemical supercapacitors (ESCs) is a topic of increasing interest because of their promising applications in biomedicine (e.g. for energy storage in autonomous implantable devices). In this work an unsaturated polyesteramide that contains phenylalanine, butenediol and fumarate as building blocks has been photo-crosslinked to obtain a hydrogel (UPEA-h). The structure of UPEA-h, which is characterized by a network of open interconnected pores surrounded by regions with compact morphology, favors ion transport, while the biodegradability and biocompatibility conferred by the α-amino acid unit and the ester group are appropriated for its usage in the biomedical field. Voltammetric and galvanostatic assays have been conducted to evaluate the behavior of UPEA-h when used as SE in ESCs with poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes. Hence, PEDOT/UPEA-h devices displayed supercapacitor response of up 179 F/g and capacitance retention higher than 90%. Moreover, the long-term stability, leakage-current, and self-discharging response of PEDOT/UPEA-h ESCs reflect the great potential of UPEA-h as ion-conductive electrolyte. Indeed, the performance of PEDOT/UPEA-h is higher than found in analogous devices constructed using other biohydrogels as SE (e.g. κ-carrageenan, poly-γ-glutamic acid and cellulose hydrogels).

JTD Keywords: Energy storage, Hydrogel electronics, Ion conductivity, Photo-crosslinking, Wearable electronics

Cellulose-based supercapacitors display important advantages in comparison with devices fabricated with other materials, regarding environmental friendliness, flexibility, cost and versatility. Recent progress in the field has been mainly focused on the utilization of cellulose fibres as: structural mechanical reinforcement of electrodes; precursors of electrically active carbon-based materials; or primary electrolytes that act as reservoirs of secondary electrolytes. In this work, a flexible, lightweight, robust, portable and manageable all-carboxymethyl cellulose symmetric supercapacitor has been obtained by assembling two electrodes based on carboxymethyl cellulose hydrogels to a solid electrolytic medium formulated with the same material. Hydrogels, which were made by cross-linking carboxymethyl cellulose paste with citric acid in water, rendered not only effective solid electrolytic media by simply loading NaCl but also electroactive electrodes. For the latter, conducting polymer microparticles, which were loaded into the hydrogel network during the physical cross-linking step, were appropriately connected through the in situ anodic polymerization of a similar conducting polymer in aqueous medium, thus creating conduction paths. The performance of the assembled supercapacitors has been proved by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. This design opens a new window for the green and mass production of flexible cellulose-based supercapacitors.

JTD Keywords: Conducting polymer, Energy storage, Flexible electrodes, In situ polymerization, Wearable electronics