Functional composites by programming entropy-driven nanosheet growth.

Nanomaterials must be systematically designed to be technologically viable1-5. Driven by optimizing intermolecular interactions, current designs are too rigid to plug in new chemical functionalities and cannot mitigate condition differences during integration6,7. Despite extensive optimization of building blocks and treatments, accessing nanostructures with the required feature sizes and chemistries is difficult. Programming their growth across the nano-to-macro hierarchy also remains challenging, if not impossible8-13. To address these limitations, we should shift to entropy-driven assemblies to gain design flexibility, as seen in high-entropy alloys, and program nanomaterial growth to kinetically match target feature sizes to the mobility of the system during processing14-17. Here, following a micro-then-nano growth sequence in ternary composite blends composed of block-copolymer-based supramolecules, small molecules and nanoparticles, we successfully fabricate high-performance barrier materials composed of more than 200 stacked nanosheets (125 nm sheet thickness) with a defect density less than 0.056 µm-2 and about 98% efficiency in controlling the defect type. Contrary to common perception, polymer-chain entanglements are advantageous to realize long-range order, accelerate the fabrication process (<30 min) and satisfy specific requirements to advance multilayered film technology3,4,18. This study showcases the feasibility, necessity and unlimited opportunities to transform laboratory nanoscience into nanotechnology through systems engineering of self-assembly.

Multidrug-resistant bacterial infections after liver transplantation: Prevalence, impact, and risk factors.

BACKGROUND & AIMS: Infections by multidrug-resistant bacteria (MDRB) are an increasing healthcare problem worldwide. This study analyzes the incidence, burden, and risk factors associated with MDRB infections after liver transplant(ation) (LT). METHODS: This retrospective, multicenter cohort study included adult patients who underwent LT between January 2017 and January 2020. Risk factors related to pre-LT disease, surgical procedure, and postoperative stay were analyzed. Multivariate logistic regression analysis was performed to identify independent predictors of MDRB infections within the first 90 days after LT. RESULTS: We included 1,045 LT procedures (960 patients) performed at nine centers across Spain. The mean age of our cohort was 56.8 ± 9.3 years; 75.4% (n = 782) were male. Alcohol-related liver disease was the most prevalent underlying etiology (43.2.%, n = 451). Bacterial infections occurred in 432 patients (41.3%) who presented with a total of 679 episodes of infection (respiratory infections, 19.3%; urinary tract infections, 18.5%; bacteremia, 13.2% and cholangitis 11%, among others). MDRB were isolated in 227 LT cases (21.7%) (348 episodes). Enterococcus faecium (22.1%), Escherichia coli (18.4%), and Pseudomonas aeruginosa (15.2%) were the most frequently isolated microorganisms. In multivariate analysis, previous intensive care unit admission (0-3 months before LT), previous MDRB infections (0-3 months before LT), and an increasing number of packed red blood cell units transfused during surgery were identified as independent predictors of MDRB infections. Mortality at 30, 90, 180, and 365 days was significantly higher in patients with MDRB isolates. CONCLUSION: MDRB infections are highly prevalent after LT and have a significant impact on prognosis. Enterococcus faecium is the most frequently isolated multi-resistant microorganism. New pharmacological and surveillance strategies aimed at preventing MDRB infections after LT should be considered for patients with risk factors. IMPACT AND IMPLICATIONS: Multidrug-resistant bacterial infections have a deep impact on morbidity and mortality after liver transplantation. Strategies aimed at improving prophylaxis, early identification, and empirical treatment are paramount. Our study unveiled the prevalence and main risk factors associated with these infections, and demonstrated that gram-positive bacteria, particularly Enterococcus faecium, are frequent in this clinical scenario. These findings provide valuable insights for the development of prophylactic and empirical antibiotic treatment protocols after liver transplantation.

Environmental prospective of valorizing corn processing effluent to produce ferulic acid grafted chitosan polymer.

The food industry requires new production models that include more environmentally friendly waste management practices, considering that the environmental loads of solid waste and wastewater associated with this sector cause damage to the receiving ecosystems. The approach considered in this study focuses on the design and environmental assessment of an enzymatic process for the valorization of ferulic acid present in the effluent of a corn tortilla plant. The ferulic acid can be immobilized on chitosan so that the ferulic acid grafted chitosan can be used as a bioactive film with enhanced antioxidant properties with potential applications in the biotechnology sector. Its real projection approach requires the evaluation of its environmental and economic performance, trying to identify its benefits and potential in the value chain, using the Techno-Economic Analysis (TEA) as a phase for the conceptual design of the process and the Life Cycle Assessment (LCA) methodology for the environmental evaluation. It should be noted that the TEA indicators are promising, since the values of the financial indicators obtained are representative of the economic profitability, which makes the ferulic acid valorization a viable process. In terms of the environmental impact of the process, the buffer dose and the chitosan production process are identified as the main critical points. This double benefit in environmental and economic terms shows that the valorization of ferulic acid for chitosan functionalization is a promising alternative to improve the sustainability performance of corn processing.

Knowledge of undergraduate and postgraduate dental students about managing traumatic dental injuries based on the 2020 International Association of Dental Traumatology guidelines: A online survey of 10 dental schools from 10 countries.

BACKGROUND/AIM: The knowledge of dental students about managing traumatic dental injuries (TDIs) may not be uniform, depending on global location and dental education. The aim of this study was to evaluate the level of knowledge of undergraduate and postgraduate students specializing in endodontics and pediatric dentistry at 10 dental schools in 10 countries about the 2020 International Association of Dental Traumatology (IADT) guidelines regarding the management of TDIs. MATERIALS & METHODS: A previously published questionnaire was used in the current survey. It was an online survey with 12 questions regarding the management of TDIs and some additional questions regarding sociodemographic and professional profiles of the participants were added. The survey was distributed to final-year undergraduate students and postgraduate students in pediatric dentistry and endodontics from 10 dental schools. Simple frequency distributions and descriptive statistics were predominantly used to describe the data. Differences in the median percentage scores among the student categories were assessed using the Kruskal-Wallis test followed by Dwass-Steel-Critchlow-Fligner pairwise comparisons. RESULTS: A total of 347 undergraduates, 126 postgraduates in endodontics, and 72 postgraduates in pediatric dentistry from 10 dental schools participated in this survey. The postgraduates had a significantly higher percentage score for correct responses compared with the undergraduates. No significant difference was observed between the endodontic and pediatric dentistry postgraduates. CONCLUSION: The knowledge possessed by undergraduate and postgraduate students concerning the IADT-recommended management of TDIs varied across the globe and some aspects were found to be deficient. This study emphasizes the critical importance of reassessing the teaching and learning activities pertaining to the management of TDIs.

Cross-Cultural Validation of the TeamSTEPPS Teamwork Perceptions Questionnaire-Spanish in Colombia.

BACKGROUND: Teamwork influences health care quality and patient safety. Yet, validated instruments for assessing teamwork in Colombia are lacking. PURPOSE: The purpose of this study was to validate the Spanish version of the TeamSTEPPS-Teamwork Perceptions Questionnaire (T-TPQ-S) for the Colombian health care context. METHODS: The T-TPQ-S underwent translation, cultural adaptation, and comprehensive psychometric testing, including reliability and confirmatory factor analyses and item difficulty and discrimination analyses. RESULTS: The T-TPQ-S demonstrated high internal consistency and excellent fit to the theoretical model. Item discrimination was within expected ranges, with response thresholds displaying an ascending order. The tool better differentiated subjects with low and high teamwork perceptions. CONCLUSIONS: The T-TPQ-S is an effective, reliable, and valid instrument for assessing teamwork perception among Colombian health care workers.

Influence of the incorporation of small-group practical seminars to a traditional lecture for the understanding of root canal morphology classification systems.

INTRODUCTION: This study aimed to assess if the incorporation of small-group practical seminars into a traditional lecture format improved the understanding and learning of the root canal classification systems in undergraduate students. MATERIALS AND METHODS: A small-group practical seminar was designed for 3rd year undergraduate students. The seminar consisted of the analysis of a guided summary of root canal morphology classifications, a participative discussion of several cases and drawing exercises of several internal anatomies based on the different classifications in templates presenting the external anatomy of different dental groups. Students were inquired about their perspectives on the different classifications and the learning strategies with an anonymous questionnaire. The knowledge acquired was assessed in an exam. The scores obtained were compared using the Mann-Whitney U-test with those obtained in the cohort of the previous year in which only the traditional lecture was delivered. RESULTS: Students' scores (mean = 7.7; SD = 2.5) were significantly higher (p = .006) than those from the previous cohort (mean = 6.9; SD = 2.3). Most students agreed that Ahmed's classification system was the most complete (98.8%) and intuitive (84%), but also the most difficult to understand (67%). All the students believed that the learning activity helped them understand the new classification system. CONCLUSION: The incorporation of small-group practical seminars into traditional lecture improved the understanding and learning of root canal configurations in undergraduate students. Students rated the classification system suggested by Ahmed et al. as the most complete and intuitive out of the three systems, but also the most difficult to learn.

Vacuum formed coils for MRI.

PURPOSE: To describe a digital fabrication method used for custom MRI receive coils with vacuum forming and electroless copper plating. METHODS: Our process produces intricate copper traces on curved surfaces. A three-dimensional scan of a desired anatomy is obtained and used to design coil elements. The layout is predistorted with a self built simulation of the vacuum forming process and the geometric overlaps are tested with electromagnetic simulation software. The desired coil geometry is patterned onto a polycarbonate sheet by sandblasting through a tape mask. The sandblasted areas are then catalyzed with a palladium-tin solution and vacuum formed. The catalyzed, three-dimensional part is placed into a custom built plating tank and copper plated. Electronic components are attached to the copper traces to form resonant receive coils. The methods described here are demonstrated and tested with an 8 channel visual cortex coil array. RESULTS: The prototype coils exhibit quality factor ratios higher than three, indicating body noise dominance. The coil array shows high signal-to-noise ratio (SNR) near the periphery of a head shaped phantom. In vivo images with up to 0 . 37 × 0 . 37 × 0 . 67 mm 3 $$ 0.37\times 0.37\times 0.67\;{\mathrm{mm}}^3 $$ spatial resolution were acquired on a human volunteer. CONCLUSION: This work presents the first example of vacuum formed coils with direct electroless copper plating. Our fabrication method results in coil arrays that are in close proximity to the body. This methods described here may enable the rapid development of a set of coils of different sizes for applications including longitudinal fMRI studies and MR-guided therapies.

Caterpillar traps: A highly flexible, distributed system of toroidal cable traps.

PURPOSE: Coil arrays are connected to the main MRI system with long, shielded coaxial cables. RF coupling of these cables to the main transmit coil can cause high shield currents, which pose risks of heating and RF burns. High-blocking resonant RF traps are placed at distinct positions along cables to mitigate these currents. Traditional traps are designed to be stiff to avoid changes in their resonant frequency, hindering the overall system flexibility. Instead of using a few high-blocking traps, we propose the use of caterpillar traps-a distributed system of small, elastic traps that cover the full length of cables. METHODS: We leverage an array of resonant toroids as traps, forming a caterpillar-like structure whereby bending only impacts individual traps minimally. Benchtop measurements are used to determine the blocking of caterpillar traps and show their robustness to bending. We also compare an anterior array system cable covered with caterpillar traps to a commercial cable with B1 + and heating measurements. RESULTS: Benchtop experiments with caterpillar traps demonstrate high robustness to bending. B1 + mapping experiments of an anterior array cable show improved blocking and flexibility compared to a commercial cable. CONCLUSION: Caterpillar traps provide sufficient attenuation to shield currents while allowing cable flexibility. Our distributed design can provide high blocking efficiency at different positions and orientations, even in cases where commercial cable traps cannot.

Transfusion-associated adverse events incidence and severity after the implementation of an active hemovigilance program with 24 h follow-up. A prospective cohort study.

BACKGROUND: Hemovigilance (HV) is usually based on voluntary reports (passive HV). Our aim is to ascertain credible incidence, severity, and mortality of transfusion-associated adverse events (TAAEs) using an active HV program. STUDY DESIGN AND METHODS: Prospective cohort study to estimate transfusion risk after 46,488 transfusions in 5830 patients, using an active HV program with follow-up within the first 24 h after transfusion. We compared these results to those with the previously established passive HV program during the same 30 months of the study. We explored factors associated with the occurrence of TAAEs using generalized estimating equations models. RESULTS: With the active HV program TAAEs incidence was 57.3 (95% CI, 50.5-64.2) and mortality 1.1 (95% CI, 0.13-2.01) per 10,000 transfusions. Incidence with the new surveillance model was 14.0 times higher than with the passive. Most events occurred when transfusions had already finished (60.2%); especially pulmonary events (80.4%). Three out of five deaths and 50.3% of severe TAAEs were pulmonary. In the multivariate analysis surgical patients had half TAAEs risk when compared to medical patients (OR, 0.53; 95% CI, 0.34-0.78) and women had nearly twice the risk of a pulmonary event compared to men (OR, 1.84; 95% CI, 1.03-3.32). Patient's age, blood component type, or blood component shelf-life were unrelated to TAAEs risk. DISCUSSION: Active hemovigilance programs provide additional data which may lead to better recognition and understanding of TAAEs and their frequency and severity.

Effectiveness of root canal instrumentation for the treatment of apical periodontitis: A systematic review and meta-analysis.

BACKGROUND: The development of endodontic instruments has rapidly advanced, but their impact on endodontic outcome parameters remains unclear. OBJECTIVES: This systematic review aimed to answer the following PICOT questions: In patients with apical periodontitis (P) what is the effectiveness of root canal instrumentation ([Q1] performed with contemporary techniques [I] in comparison with 'traditional' techniques [C]] and ([Q2] performed with contemporary engine-driven NiTi instruments [I] compared with other types of contemporary engine-driven NiTi instruments [with different design and/or technology] [C]) in terms of clinical and patient-related outcomes (O)? METHODS: After PROSPERO protocol registration, a literature search was conducted using Clarivate Analytics' Web of Science, Scopus, PubMed and Cochrane Central Register of Controlled Trials. Grey literature and major journal contents were examined. Two independent reviewers performed the study selection, data extraction and appraisal of included studies. A quantitative meta-analysis was considered, and statistical heterogeneity and overall quality of evidence were assessed. RESULTS: Nine studies were identified showing substantial methodological differences. Five studies addressed PICOT 1 and three PICOT 2, whereas one study aimed both. A random-effects meta-analysis model was considered for the outcome 'radiographic evidence of normal periodontal ligament space or reduction of apical lesion size' (PICOT 1) based on three studies with 332 evaluable participants and showed that contemporary instrumentation was associated with a more favourable outcome (p = .005) compared with root canal preparation with stainless steel instruments (odds ratio = 2.07 [95%-confidence interval = 1.25-3.44]) with no evidence of statistical heterogeneity (I2  = 0%) but low quality of evidence. DISCUSSION: Albeit a few studies fulfilled eligible criteria, no study had a low risk of bias. Compelling evidence indicating significantly different outcome rates using different endodontic instruments when treating teeth with apical periodontitis is lacking. CONCLUSIONS: In terms of healing, the results of the meta-analysis determined the higher effectiveness of root canal instrumentation performed with contemporary techniques in comparison with conventional stainless steel instruments in patients with apical periodontitis followed for a minimum of 1 year with low quality of evidence. No differences could be demonstrated between preparations with traditional stainless steel and contemporary NiTi instruments for other clinical and patient-related outcomes. REGISTRATION: PROSPERO (CRD42021274642).

PROBE 2023 guidelines for reporting observational studies in Endodontics: A consensus-based development study.

Observational studies are non-interventional studies that establish the prevalence and incidence of conditions or diseases in populations or analyse the relationship between health status and other variables. They also facilitate the development of specific research questions for future randomized trials or to answer important scientific questions when trials are not possible to carry out. This article outlines the previously documented consensus-based approach by which the Preferred Reporting items for Observational studies in Endodontics (PROBE) 2023 guidelines were developed. A steering committee of nine members was formed, including the project leaders (PD, VN). The steering committee developed an initial checklist by combining and adapting items from the STrengthening the Reporting of Observational studies in Epidemiology (STROBE) checklist and the Clinical and Laboratory Images in Publications (CLIP) principles, as well as adding several new items specifically for the specialty of Endodontics. The steering committee then established a PROBE Delphi Group (PDG) and a PROBE Online Meeting Group (POMG) to obtain expert input and feedback on the preliminary draft checklist. The PDG members participated in an online Delphi process to reach consensus on the clarity and suitability of the items present in the PROBE checklist. The POMG then held detailed discussions on the PROBE checklist generated through the online Delphi process. This online meeting was held via the Zoom platform on 7th October 2022. Following this meeting, the steering committee revised the PROBE checklist, which was piloted by several authors when preparing a manuscript describing an observational study for publication. The PROBE 2023 checklist consists of 11 sections and 58 items. Authors are now encouraged to adopt the PROBE 2023 guidelines, which will improve the overall reporting quality of observational studies in Endodontics. The PROBE 2023 checklist is freely available and can be downloaded from the PRIDE website (https://pride-endodonticguidelines.org/probe/).

Synthesis of Chalcones: An Improved High-Yield and Substituent-Independent Protocol for an Old Structure.

Chalcones are a type of molecule that can be considered as easily synthesizable through aldol condensation or that can be readily purchased from habitual commercial vendors. However, on reviewing the literature, one realizes that there are no standard procedures for such aldol condensations, that there exists a wide range of alternative methods for the aldol condensation (indicating that such a condensation is not always simple), and that, in many cases, low yields are obtained that involve purifications by recrystallization or column chromatography. To develop a robust standard protocol independent of the nature of the substituents present on the acetophenone or the benzaldehyde involved in the aldol condensation leading to the chalcone, we made a comparison between an aldol condensation in KOH/EtOH and a Wittig reaction between the corresponding ylide and benzaldehyde in water. We describe an improved procedure for the Wittig reaction and a protocol for the elimination of the Ph3P=O byproduct (and the excess of ylide used) by filtration of the crude reaction product through a silica gel plug. We thus demonstrate that such an improved procedure can be a general method for the synthesis of chalcones in high yield and excellent purity and is clearly an improvement on the classical aldol condensation.

Comparison of SARS-CoV-2 viral load in asymptomatic and symptomatic children attended in a referral public pediatric hospital in Argentina.

At present, different reports have shown that children reach similar SARS-CoV-2 viral load (VL) levels compared to adults; however, the impact of VL on children remains ambiguous when asymptomatic versus symptomatic cases are compared. Thus, the aim of this study was to assess VL at the time of diagnosis in asymptomatic and symptomatic SARS-CoV-2 infected children. VL analysis was retrospectively carried out from nasopharyngeal swabs on 82 SARS-CoV-2 infected children, from March to October 2020. Of the 82 children, 31 were asymptomatic. Symptomatic patients had significantly higher VL values compared to asymptomatic ones (median=7.41 vs 4.35log10 copies/ml, respectively). Notwithstanding, 8 out of 31 asymptomatic children had high VL levels, overlapping levels observed above the first quartile in the symptomatic group. Analysis of different age groups revealed that median VL values were higher in the symptomatic groups, although there was only a significant difference in children younger than 5 years of age. On the other hand, there was no significant difference between the VL values from the 82 SARS-CoV-2 infected children according to age, sex, underlying disease, symptoms or severity of COVID-19 related disease. This study emphasizes the importance of VL analysis in SARS-CoV-2 infected children, who could contribute to viral spread in the community. This concern could be extended to healthcare workers, who are in contact with children.

Present status and future directions: Canal shaping.

This narrative review will focus on the evolution, present and future of engine-driven root canal preparation. Root canal preparation changed drastically when Walia in 1988 introduced the use of nickel-titanium (NiTi) alloys in Endodontics. In 2013, five generations of NiTi endodontic instruments had been established based on their metallurgical, mechanical properties and design features. Since then, manufacturers have been introducing further major changes in instrument design and characteristics that have not been translated in new recognized generations of instruments. In general, those changes have demonstrated enhanced instrument properties, but it is not clear yet if all those improvements are directly translated to an improvement in clinical success. This narrative review attempts to address the present status of engine-driven instruments in terms of both evidence from laboratory-based studies and clinical data, to identify potential further generations of instruments, and last to anticipate future directions for research and development.

Printed Potentiometric Nitrate Sensors for Use in Soil.

Plant-available nitrogen, often in the form of nitrate, is an essential nutrient for plant growth. However, excessive nitrate in the environment and watershed has harmful impacts on natural ecosystems and consequently human health. A distributed network of nitrate sensors could help to quantify and monitor nitrogen in agriculture and the environment. Here, we have developed fully printed potentiometric nitrate sensors and characterized their sensitivity and selectivity to nitrate. Each sensor comprises an ion-selective electrode and a reference electrode that are functionalized with polymeric membranes. The sensitivity of the printed ion-selective electrodes was characterized by measuring their potential with respect to a commercial silver/silver chloride reference electrode in varying concentrations of nitrate solutions. The sensitivity of the printed reference electrodes to nitrate was minimized with a membrane containing polyvinyl butyral (PVB), sodium chloride, and sodium nitrate. Selectivity studies with sulphate, chloride, phosphate, nitrite, ammonium, calcium, potassium, and magnesium showed that high concentrations of calcium can influence sensor behavior. The printed ion-selective and reference electrodes were combined to form a fully printed sensor with sensitivity of -48.0 ± 3.3 mV/dec between 0.62 and 6200 ppm nitrate in solution and -47 ± 4.1 mV/dec in peat soil.

1H-Pyrazolo[3,4-b]pyridines: Synthesis and Biomedical Applications.

Pyrazolo[3,4-b]pyridines are a group of heterocyclic compounds presenting two possible tautomeric forms: the 1H- and 2H-isomers. More than 300,000 1H-pyrazolo[3,4-b]pyridines have been described which are included in more than 5500 references (2400 patents) up to date. This review will cover the analysis of the diversity of the substituents present at positions N1, C3, C4, C5, and C6, the synthetic methods used for their synthesis, starting from both a preformed pyrazole or pyridine, and the biomedical applications of such compounds.

Multibiomarker approach in fish to assess a heavily polluted Brazilian estuary, Guanabara Bay.

Brazil's Guanabara Bay (GB), located in Rio De Janeiro, is a deeply contaminated, eutrophic waterbody that challenges the understanding of the effects of pollutants on the biota. This paper presents a strategy to evaluate the impact of contamination utilizing a multibiomarker approach in two fish species: corvine (Micropogonias furnieri) and burrfish (Chilomycterus spinosus). The strategy is comprised of a general biomarker of fish' physical condition, the condition factor (CF), and specific biomarkers of pollutant exposure such as acetylcholinesterase (AChE), metallothionein (MT) activity and biliary polycyclic aromatic hydrocarbons (PAH) metabolites. Our results indicate that fish from GB are greatly affected by environmental pollution. CF values were lower in fishes from GB than in the reference site indicating that these fishes were under higher environmental stress. Lower AChE activity level in both species showed vulnerability to the presence of pesticide residues. Higher levels of MT in both species in GB reflect the consequences of heavy metal exposure in the bay, in spite of their bioavailability being restricted specially by the high organic matter content of GB. The levels of PAHs were higher in GB for both fish species, indicating exposure to these substances. However, the fish species showed different behavior regarding the origin of the PAHs. The multibiomarker approach used in this study evidently depicted effects on the health of fish in a waterbody with a complex polluted situation and further categorized the effects of anthropogenic activities in this aquatic system.

Quantitative anatomy mimicking slice phantoms.

PURPOSE: To present a reproducible methodology for building an anatomy mimicking phantom with targeted T1 and T2 contrast for use in quantitative magnetic resonance imaging. METHODS: We propose a reproducible method for creating high-resolution, quantitative slice phantoms. The phantoms are created using gels with different concentrations of NiCl2 and MnCl2 to achieve targeted T1 and T2 values. We describe a calibration method for accurately targeting anatomically realistic relaxation pairs. In addition, we developed a method of fabricating slice phantoms by extruding 3D printed walls on acrylic sheets. These procedures are combined to create a physical analog of the Brainweb digital phantom. RESULTS: With our method, we are able to target specific T1 /T2 values with less than 10% error. Additionally, our slice phantoms look realistic since their geometries are derived from anatomical data. CONCLUSION: Standardized and accurate tools for validating new techniques across sequences, platforms, and different imaging sites are important. Anatomy mimicking, multi-contrast phantoms designed with our procedures could be used for evaluating, testing, and verifying model-based methods.

A flexible organic reflectance oximeter array.

Transmission-mode pulse oximetry, the optical method for determining oxygen saturation in blood, is limited to only tissues that can be transilluminated, such as the earlobes and the fingers. The existing sensor configuration provides only single-point measurements, lacking 2D oxygenation mapping capability. Here, we demonstrate a flexible and printed sensor array composed of organic light-emitting diodes and organic photodiodes, which senses reflected light from tissue to determine the oxygen saturation. We use the reflectance oximeter array beyond the conventional sensing locations. The sensor is implemented to measure oxygen saturation on the forehead with 1.1% mean error and to create 2D oxygenation maps of adult forearms under pressure-cuff-induced ischemia. In addition, we present mathematical models to determine oxygenation in the presence and absence of a pulsatile arterial blood signal. The mechanical flexibility, 2D oxygenation mapping capability, and the ability to place the sensor in various locations make the reflectance oximeter array promising for medical sensing applications such as monitoring of real-time chronic medical conditions as well as postsurgery recovery management of tissues, organs, and wounds.

Characterization and Comparison of Biodegradable Printed Capacitive Humidity Sensors.

Flexible and biodegradable sensors are advantageous for their versatility in a range of areas from smart packaging to agriculture. In this work, we characterize and compare the performance of interdigitated electrode (IDE) humidity sensors printed on different biodegradable substrates. In these IDE capacitive devices, the substrate acts as the sensing layer. The dielectric constant of the substrate increases as the material absorbs water from the atmosphere. Consequently, the capacitance across the electrodes is a function of environmental relative humidity. Here, the performance of polylactide (PLA), glossy paper, and potato starch as a sensing layer is compared to that of nonbiodegradable polyethylene terephthalate (PET). The capacitance across inkjet-printed silver electrodes is measured in environmental conditions ranging from 15 to 90% relative humidity. The sensitivity, response time, hysteresis, and temperature dependency are compared for the sensors. The relationship between humidity and capacitance across the sensors can be modeled by exponential growth with an R2 value of 0.99, with paper and starch sensors having the highest overall sensitivity. The PET and PLA sensors have response and recovery times under 5 min and limited hysteresis. However, the paper and starch sensors have response and recovery times closer to 20 min, with significant hysteresis around 100%. The PET and starch sensors are temperature independent, while the PLA and paper sensors display thermal drift that increases with temperature.