Some NASA contributions to human factors engineering: A survey

This survey presents the NASA contributions to the state of the art of human factors engineering, and indicates that these contributions have a variety of applications to nonaerospace activities. Emphasis is placed on contributions relative to man's sensory, motor, decisionmaking, and cognitive behavior and on applications that advance human factors technology

Analysis of Consistency of Transthoracic Bioimpedance Measurements Acquired with Dry Carbon Black PDMS Electrodes, Adhesive Electrodes, and Wet Textile Electrodes

The detection of intrathoracic volume retention could be crucial to the early detection of decompensated heart failure (HF). Transthoracic Bioimpedance (TBI) measurement is an indirect, promising approach to assessing intrathoracic fluid volume. Gel-based adhesive electrodes can produce skin irritation, as the patient needs to place them daily in the same spots. Textile electrodes can reduce skin irritation; however, they inconveniently require wetting before each use and provide poor adherence to the skin. Previously, we developed waterproof reusable dry carbon black polydimethylsiloxane (CB/PDMS) electrodes that exhibited a good response to motion artifacts. We examined whether these CB/PDMS electrodes were suitable sensing components to be embedded into a monitoring vest for measuring TBI and the electrocardiogram (ECG). We recruited N = 20 subjects to collect TBI and ECG data. The TBI parameters were different between the various types of electrodes. Inter-subject variability for copper-mesh CB/PDMS electrodes and Ag/AgCl electrodes was lower compared to textile electrodes, and the intra-subject variability was similar between the copper-mesh CB/PDMS and Ag/AgCl. We concluded that the copper mesh CB/PDMS (CM/CB/PDMS) electrodes are a suitable alternative for textile electrodes for TBI measurements, but with the benefit of better skin adherence and without the requirement of wetting the electrodes, which can often be forgotten by the stressed HF subjects

Comparison of silver-plated nylon (Ag/PA66) e-textile and Ag/AgCl electrodes for bioelectrical impedance analysis (BIA)

Recently, researchers have adapted Bioelectrical Impedance Analysis (BIA) as a new approach to objectively monitor wounds. They have indicated various BIA parameters associated to specific wound types can be linked to wound healing through trend analysis relative to time. However, these studies are conducted using wet electrodes which have been identified as possessing several shortcomings, such as unstable measurements. Thus, the adaption of e-textile electrodes has become an area of interest in measuring biosignals. E-textile electrodes are known to possess a significantly large polarization impedance (Zp) that potentially influences these biosignal measurements. In this study we aim to identify the suitability of e-textile electrodes to monitor wounds using BIA methodologies. By adapting suggested methodologies conducted in-vivo from previous studies, we used an ex-vivo model to observe the behaviour of e-textile electrodes relative to time. This was compared to common clinical wet electrodes, specifically Ag/AgCl. The objective of this study was to identify the BIA parameters that can be used to monitor wounds with e-textile electrodes. By analysing the BIA parameters relative to time, we observed the influence of Zp on these parameters.Peer ReviewedPostprint (author's final draft

Using the redundant convolutional encoder–decoder to denoise QRS complexes in ECG signals recorded with an armband wearable device

Long-term electrocardiogram (ECG) recordings while performing normal daily routines are often corrupted with motion artifacts, which in turn, can result in the incorrect calculation of heart rates. Heart rates are important clinical information, as they can be used for analysis of heart-rate variability and detection of cardiac arrhythmias. In this study, we present an algorithm for denoising ECG signals acquired with a wearable armband device. The armband was worn on the upper left arm by one male participant, and we simultaneously recorded three ECG channels for 24 h. We extracted 10-s sequences from armband recordings corrupted with added noise and motion artifacts. Denoising was performed using the redundant convolutional encoder–decoder (R-CED), a fully convolutional network. We measured the performance by detecting R-peaks in clean, noisy, and denoised sequences and by calculating signal quality indices: signal-to-noise ratio (SNR), ratio of power, and cross-correlation with respect to the clean sequences. The percent of correctly detected R-peaks in denoised sequences was higher than in sequences corrupted with either added noise (70–100% vs. 34–97%) or motion artifacts (91.86% vs. 61.16%). There was notable improvement in SNR values after denoising for signals with noise added (7–19 dB), and when sequences were corrupted with motion artifacts (0.39 dB). The ratio of power for noisy sequences was significantly lower when compared to both clean and denoised sequences. Similarly, cross-correlation between noisy and clean sequences was significantly lower than between denoised and clean sequences. Moreover, we tested our denoising algorithm on 60-s sequences extracted from recordings from the Massachusetts Institute of Technology-Beth Israel Hospital (MIT-BIH) arrhythmia database and obtained improvement in SNR values of 7.08 ± 0.25 dB (mean ± standard deviation (sd)). These results from a diverse set of data suggest that the proposed denoising algorithm improves the quality of the signal and can potentially be applied to most ECG measurement devices

NANOCOMPOSITE BIOELECTRONICS FOR BIOPOTENTIAL ENABLED PROSTHESIS

Soft material-enabled electronics can demonstrate extreme mechanical flexibility and stretchability. Such compliant, comfortable electronics allow continuous, long-term measurement of biopotentials on the skin. Manufacturing of the stretchable electronic devices is enabled by the recent development combining materials transfer printing and microfabrication. However, the existing method using inorganic materials and multi-layered polymers requires long material preparation time and expensive processing cost due to the requirement of microfabrication tools and complicated transfer printing steps. Here, this study develops a new fabrication method of soft electronics via a micro-replica-molding technique, which allows fast production, multiple use, and low cost by avoiding microfabrication and multiple transfer printing. The core materials, carbon nanomaterials integrated with soft elastomers, further reduces the entire production cost, compared to costly metals such as gold and silver, while offering mechanical compliance. Collectively, skin-wearable electrodes, designed by optimized materials and fabrication method enable a high-fidelity measurement of non-invasive electromyograms on the skin for advanced human-machine interface, targeting prosthesis

신축성 있고 착용 가능한 탄소 나노튜브 기반 전자 기술

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 협동과정 바이오엔지니어링전공, 2020. 8. 김대형.Networks of carbon nanotubes (CNTs) are a promising candidate for use as a basic building block for next-generation soft electronics, owing to their superior mechanical and electrical properties, chemical stability, and low production cost. In particular, the CNTs, which are produced as a mixture of metallic and semiconducting CNTs via chemical vapor deposition, can be sorted according to their electronic types, which makes them useful for specific purposes: semiconducting CNTs can be employed as channel materials in transistor-based applications and metallic CNTs as electrodes. However, the development of CNT-based electronics for soft applications is still at its infant stage, mainly limited by the lack of solid technologies for developing high-performance deformable devices whose electrical performances are comparable to those fabricated using conventional inorganic materials. In this regard, soft CNT electronics with high mechanical stability and electrical performances have been pursued. First, wearable nonvolatile memory modules and logic gates were fabricated by employing networks of semiconducting CNTs as the channel materials, with strain-tolerant device designs for high mechanical stability. The fabricated devices exhibited low operation voltages, high device-to-device uniformity, on/off ratios, and on-current density, while maintaining its performance during ~30% stretching after being mounted on the human skin. In addition, various functional logic gates verified the fidelity of the reported technology, and successful fabrication of non-volatile memory modules with wearable features has been reported for the first time at the time of publication. Second, the networks of semiconducting CNTs were used to fabricate signal amplifiers with a high gain of ~80, which were then used to amplify electrocardiogram (ECG) signals measured using a wearable sensor. At the same time, color-tunable organic light-emitting diodes (CTOLEDs) were developed based on ultra-thin charge blocking layer that controlled the flow of excitons during different voltage regimes. Together, they were integrated to construct a health monitoring platform whereby real-time ECG signals could be detected while simultaneously notifying its user of the ECG status via color changes of the wearable CTOLEDs. Third, intrinsically stretchable CNT transistors were developed, which was enabled by the developments of thickness controllable, vacuum-deposited stretchable dielectric layer and vacuum-deposited metal thin films. Previous works employed strain-tolerant device designs which are based on the use of filamentary serpentine-shaped interconnections, which severely sacrifice the device density. The developed stretchable dielectric, compatible with the current vacuum-based microfabrication technology, exhibited excellent insulating properties even for nanometer-range thicknesses, thereby enabling significant electrical performance improvements such as low operation voltage and high device uniformity/reproducibility, which has not been realized in the most advanced intrinsically stretchable transistors of today.탄소 나노튜브는 뛰어난 전기적, 화학적, 그리고 기계적 특성을 갖고 있어 차세대 유연 전자소자의 핵심 소재 중 하나로 각광을 받고 있으나, 아직까지 이를 이용한 실용적인 유연 전자소자의 개발은 실현되지 않고 있다. 이는 탄소 나노튜브의 전기적 특성대로 완벽히 분류해 낼 수 있는 기술, 탄소 나노튜브를 소자의 원하는 위치에 정확히 원하는 양만큼 네트워크 형태 혹은 정렬된 형태로 증착하는 기술, 그리고 유연 전자소자를 구성하는 다른 물질들의 개발 기술의 부재 때문이다. 지난 10여년간 해당 기술들은 광범위하게 연구되어지고 있으나, 탄소 나노튜브를 활용한 우수한 유연 전자소자 개발을 위한 핵심 기술들의 발전은 아직 초기 단계에 있다. 따라서 이 논문을 통해 탄소 나노튜브를 유연 전자소자에 적용시킬 수 있는 새로운 기술을 소개하고자 한다. 첫번째로 탄소 나노튜브와 유연 전자소자의 소자 디자인을 이용하여 피부위에 증착 가능한 비휘발성 메모리 소자를 제작하였고, 해당 기술을 이용하여 피부위에서 안전하게 동작할 수 있는 다양한 기초 회로들을 구현하였다. 탄소 나노튜브 기반 메모리 전자 소자 및 회로는 다양한 외부 응력이 가해져도 안정적으로 동작을 하였고, 개발된 기술을 통해 보다 실용적인 탄소 나노튜브 기반 유연 전자 소자의 제작 조건을 확립할 수 있었다. 두번째로 위에 개발된 기술을 바탕으로, 보다 복잡한 탄소 나노튜브 기반 유연 회로 및 구동전압에 따라 발광색이 변환하는 색변환 소자를 제작하여 해당 소자들이 피부위에 부착되어 잘 작동되도록 구현하였다. 그리고 이 두 가지 웨어러블 전자소자를 통합하여 실시간으로 심전도를 측정하여 탄소 나노튜브 기반 전자소자를 통해 해당 신호를 증폭시키고, 신호의 상태를 색변환 소자로 나타낼 수 있는 심전도 모니터 시스템을 구현하였다. 세번째로 진공 증착이 가능한 유연 절연체를 개발하여, 기존의 유연 전자소자들이 가지고 있던 극명한 한계를 극복하였다 (높은 구동 전압, 낮은 집적도, 대면적 소자 선능 균일도 등). 기존의 액상 기반 증착을 위주로 한 유연 전자 소자들은 무기물질 기반 전자소자 대비 극심한 성능 저하를 보여주었는데, 이를 해결하기 위해 새로운 절연물질을 개발하고 탄소 나노튜브 기반 유연 전자소자에 적용하여 그 가능성을 보여주었다.Chapter 1. Introduction 1 1.1 Discovery of CNTs and their benefits for soft electronic applications 1 1.2 Electrical sorting of CNTs 5 1.3 Deposition methods of solution-processed semiconducting CNTs 7 1.4 Conclusion 23 1.5 References 24 Chapter 2. Stretchable Carbon Nanotube Charge-Trap Floating-Gate Memory and Logic Devices for Wearable Electronics 32 2.1 Introduction 32 2.2 Experimental section 34 2.3 Results and discussion 36 2.4 Conclusion 62 2.5 References 63 Chapter 3. Wearable Electrocardiogram Monitor Using Carbon Nanotube Electronics and Color-Tunable Organic Light-Emitting Diodes 67 3.1 Introduction 67 3.2 Experimental section 70 3.3 Results and discussion 73 3.4 Conclusion 97 3.5 References 98 Chapter 4. Medium-Scale Electronic Skin Based on Carbon Nanotube Transistors with Vacuum-Deposited Stretchable Dielectric Film 102 4.1 Introduction 102 4.2 Experimental section 106 4.3 Result and discussion 111 4.4 Conclusion 135 4.5 References 136Docto

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

Opercular beat rate sensor for remote fish monitoring

O consumo de bens alimentares, nomeadamente de peixes e de outros organismos aquáticos, tem crescido ao longo dos anos devido à crescente densidade populacional, que por consequência, a produção em cativeiro e/ou em ambiente controlado tem sofrido um aumento exponencial especialmente nos últimos anos, não só devido à elevada procura derivada do crescimento populacional como também para proteção das espécies selvagens. Em ambientes de aquacultura, como todos os tipos de produção que afunilam para a otimização da produção, leia-se, produzir mais, mais rápido e em menos espaço, têm como objetivo aumentar a eficiência e consequentemente diminuir o custo de produção. Contudo, os peixes são muito sensíveis ao stress, que por sua vez está fortemente relacionado com a saúde dos mesmos. Conseguir obter informações sobre o estado de stress dos peixes é uma boa prática que permite prever ou até impedir a propagação de doenças na população. Este tipo de informações pode ser expressa pelo peixe por um conjunto de alterações fisiológicas, tais como batimento cardíaco que está relacionado com o ritmo de respiração, libertação de hormonas que podem ser medidas com uma amostra da água onde a cultura se encontra, mudanças de cor do próprio peixe, ou até mesmo mudanças comportamentais tais como alimentação e atitude (ativa ou passiva). Estas mudanças na biologia do peixe resumem-se num crescimento demorado e/ou com doenças. O objetivo deste projeto é desenvolver um dispositivo eletrónico com um sensor capacitivo para ser colocado no opérculo de um peixe de tamanho médio das conhecidas espécies Robalo e/ou Dourada, de modo a conseguir obter o ritmo de batimento do opérculo, que está diretamente relacionado com o ritmo de respiração. O dispositivo é constituído pelo sensor dois elétrodos) e por toda a eletrónica, software e firmware necessários ao funcionamento, medição e transmissão do sinal adquirido pelo sensor. O sensor deverá enviar os dados para o sistema de receção “eZ430-TMS37157” da Texas InstrumentsTM. Este sistema (eZ430-TMS37157) é composto por um recetor, uma antena e uma tag (transponder) que comunica com o sistema recetor por Rádio-Frequência (RF). O sistema recetor utilizado neste projeto já foi anteriormente estudado e modificado (de modo a permitir a utilização de antenas maiores e também mais potência de emissão) por Tiago João Barbosa de Almeida, no desenvolvimento da Tese de mestrado “Radio frequency system for remote fish monitoring in aquaculture”. O consórcio responsável pelo projeto (AquaExcell 2020) definiu que o sistema teria de comunicar com o sistema recetor por rádio frequência (RFID) à frequência de 134.2 kHz, frequência normalmente usada em sistemas de identificação eletrónica interna e/ou externa para animais. Neste projeto, foram desenvolvidos o sensor, o circuito de transmissão, firmware e software necessários para o comunicação e processamento do sinal obtido pelo sensor. Todo este conjunto compõe uma tag, que tem como objetivo substituir a tag que compõe do kit original (eZ430-TMS37157), pela tag desenvolvida em laboratório. As experiências foram implementadas em laboratório, em aquário, com um peixe impresso em uma folha de acrílico e um motor para simular o movimento do opérculo através de ímanes, estando o sensor submerso em água salgada e colocado sobre o opérculo do peixe. O aquário utilizado tem 39 cm de comprimento, 30 cm de altura e 29 cm de largura e foi utilizado com água salgada natural proveniente da praia de Faro. Os resultados das experiências são o Opercular beat-rate (OBR) em batimentos por minuto (bpm) e o sinal ADC (utilizado para calcular a OBR).Fish health and welfare are highly correlated with the stress factor. When exposed to stress, the fish exhibits changes in behavior, growth rate, among other factors. These symptoms can be accessed using different techniques, visually (with cameras or naked eyes), or measured in laboratory (hormones quantity through water sampling), among others. This project aims to develop a capacitive sensor and an electronic device with a capacitive sensor to be placed on the fish operculum, with the ability to measure the breath-rate through the opercular movements and communicate the sensed data over RF-field at the frequency of 134 kHz, a common frequency used on animal identification. The development and analysis of the capacitive sensor and the associated electronics and software and/or firmware are the main objective of this work. The reception system used to receive the data is the “eZ430-TMS37157” from Texas InstrumentsTM. The receptor system was already modified to allow the connection of bigger antennas. The experiments were carried out with a printed fish on acrylic sheet, using a standard model from seabass or golden-bream specimens, with the aid of a motor using magnets to induce the opercular movement. The aquarium used has the dimensions of 39 cm length, 30 cm height and 29 cm width, being filled with saltwater from the local region. The experiments outputs are the opercular beat-rate (OBR) in beats per minute (bpm) and the ADC signal (used for OBR calculations).O presente trabalho foi financiado pelas seguintes projetos e instituições: - Projecto AQUAEXCEL 2020 (Grant agreement ID: 652831) - Instituto de Telecomunicações (IT), UID/EEA/50008/202

Functional Polymer Gels based on Oligomer Fluids

Polymergele, wie beispielsweise Hydrogele, die aus vernetzten Polymerketten und niedermolekularen Lösungsmitteln bestehen, wurden aufgrund der Ähnlichkeit ihrer mechanischen Eigenschaften mit denen von weichen biologischen Geweben weit verbreitet in biomedizinischen Anwendungen, flexibler Elektronik und weichen Maschinen verwendet. Das Design von Polymernetzwerken und sein Beitrag zu den Eigenschaften solcher Materialien wurden ausgiebig untersucht. Die infundierten Lösungsmittel, die die innere Struktur von Gelen stark beeinflussen würden, werden jedoch selten untersucht. Ziel dieser Dissertation ist es, eine Reihe von Lösungsmittelstrategien zur Herstellung funktioneller Polymergele bereitzustellen. In Kapitel 1 wird eine allgemeine Einführung in funktionelle Polymergele basierend auf verschiedenen Lösungsmitteln gegeben, die die verschiedenen Wahlmöglichkeiten von Lösungsmitteln für Polymergele und von den Lösungsmittelstrategien abgeleitete Funktionen abdeckt. Für die Auswahl der Lösungsmittel wurden die Herstellungsmethoden und die neuesten Entwicklungen der Polymergele auf Basis verschiedener Lösungsmittel zusammengefasst, darunter organische Lösungsmittel, ionische Flüssigkeiten, tiefeutektische Lösungsmittel und Polymerflüssigkeiten. Dann wurden die aus den Lösungsmittelstrategien abgeleiteten Funktionen diskutiert, darunter rutschige Oberflächen, Gefrierbeständigkeit oder thermische Stabilität, überlegene mechanische Eigenschaften und elektrische Leistung. In Kapitel 3.1 wurde ein Polymergelsystem auf Basis von Poly(ethylenglykol) (PEG) als Flüssigphase demonstriert. Der kritische Einfluss der Lösungsmittelnatur auf die mechanischen Eigenschaften und die Leistung von weichen Polymergelen wurde untersucht. Als elastisches Polymernetzwerk wurde ein physikalisch vernetztes Copolymer aus 2-Hydroxyethylmethacrylat und Acrylsäure gewählt. Verglichen mit dem entsprechenden Gel auf Hydrogel- oder Ethylenglykolbasis weist das PEGgel außergewöhnliche physikalische Eigenschaften auf, wie z. B. hohe Dehnbarkeit und Zähigkeit, schnelle Selbstheilung und Langzeitstabilität unter Umgebungsbedingungen. Je nach Molekulargewicht und PEG-Anteil variierte die Zugfestigkeit von PEGgelen von 0,22 MPa bis 41,3 MPa, die Bruchdehnung von 12 % bis 4336 %, der Elastizitätsmodul von 0,08 MPa bis 352 MPa und die Zähigkeit von 2,89 MJ m-3 bis 56,23 MJ m-3. Die erhaltenen Polymergele können zur Herstellung eines selbstheilenden pneumatischen Aktuators durch 3D-Druck verwendet werden. Die verbesserten mechanischen Eigenschaften des PEGgel-Systems könnten auf andere Polymernetzwerke (sowohl chemisch als auch physikalisch vernetzt) ausgedehnt werden. In Kapitel 3.2 wurden Ionen in das Lösungsmittelsystem eingeführt, um ionisches PEGgel herzustellen. Der Einbau von Ionen in PEG erhöht gleichzeitig die Festigkeit und Zähigkeit der Polymergele. Das typische ionische PEGgel besteht aus in situ gebildeten, physikalisch vernetzten Poly(2-hydroxyethylmethacrylat)-Netzwerken und PEG und weist eine hohe Leitfähigkeit (0,04 S m-1), eine ausgezeichnete elektrochemische Stabilität (> 60.000 Zyklen), eine extreme Dehnbarkeit ( bis zu 1400 %), hohe Zähigkeit (7,16 MJ m-3), schnelle Selbstheilungseigenschaft, die eine Wiederherstellung der Ionenleitfähigkeit innerhalb von Sekunden ermöglicht, sowie keine Lösungsmittelleckage auf. Mehrere Anwendungen von ionischem PEGgel wurden als (a) flexible Sensoren zur Dehnungs- oder Temperaturmessung, (b) Hautelektroden zur Aufzeichnung von Elektrokardiogrammen und (c) als robustes und sensorisches Material für pneumatische künstliche Muskeln demonstriert. In Kapitel 3.3 wurde eine In-situ-Phasentrennung im PEGgel-System unter Verwendung der Mischung aus PEG und Polypropylenglykol (PPG) als Lösungsmittel gebildet. Die phasengetrennten Polymergele wurden durch direktes Polymerisieren von 2-Hydroxyethylmethacrylat in einer Mischung aus PEG und PPG hergestellt. Die polymerisierten elastischen Netzwerke weisen eine unterschiedliche Löslichkeit in PEG (hochlöslich) und PPG (schwach löslich aufgrund des vorhandenen Methyls in der Hauptkette) auf, was zu einem makroskopisch homogenen kovalenten Netzwerk mit in-situ-Phasentrennung führt. Das resultierende phasengetrennte gel zeigt eine hohe Festigkeit (8,0 MPa), eine günstige Bruchdehnung (430 %) und eine große Zähigkeit (17,0 J m-3). Die getrennten Phasen verleihen dem Polymergel eine Formgedächtniseigenschaft, die für verschiedene weiche Maschinen in Kombination mit 3D-Druckfähigkeit verwendet werden kann. Dann wurden Ionen in das PEG/PPG-Lösungsmittel eingebaut, um eine hierarchische Verbesserung in Polymergelen zu erreichen, die von den ionischen Wechselwirkungen (Nanoebene) bis zur Phasentrennung (Mikroebene) reicht. Eine solche hierarchische Struktur verbesserte die Festigkeit und Zähigkeit von Polymergelen weiter und zeigte eine hohe Bruchfestigkeit (12,2 MPa) und Bruchenergie (54 kJ m-2). Abschließend wurde ein Ausblick auf die Herausforderungen gegeben, denen man sich bei der Entwicklung funktioneller Polymergele stellen muss. Um die Entwicklung von Polymergelen in verschiedenen Bereichen zu beschleunigen, müssen wir sowohl das Netzwerkdesign als auch die Lösungsmittelstrategien optimieren. Fortschritte auf nur einer Seite reichen nicht aus, um alle Herausforderungen zu lösen

Aerospace medicine and biology: A cumulative index to the continuing bibliography of the 1973 issues

A cumulative index to the abstracts contained in Supplements 112 through 123 of Aerospace Medicine and Biology A Continuing Bibliography is presented. It includes three indexes: subject, personal author, and corporate source