High User Comfort Research Articles

Materials, Structure, and Interface of Stretchable Interconnects for Wearable Bioelectronics.

Since wearable technologies for telemedicine have emerged to tackle global health concerns, the demand for well-attested wearable healthcare devices with high user comfort also arises. Skin-wearables for health monitoring require mechanical flexibility and stretchability for not only high compatibility with the skin's dynamic nature but also a robust collection of fine health signals from within. Stretchable electrical interconnects, which determine the device's overall integrity, are one of the fundamental units being understated in wearable bioelectronics. In this review, a broad class of materials and engineering methodologies recently researched and developed are presented, and their respective attributes, limitations, and opportunities in designing stretchable interconnects for wearable bioelectronics are offered. Specifically, the electrical and mechanical characteristics of various materials (metals, polymers, carbons, and their composites) are highlighted, along with their compatibility with diverse geometric configurations. Detailed insights into fabrication techniques that are compatible with soft substrates are also provided. Importantly, successful examples of establishing reliable interfacial connections between soft and rigid elements using novel interconnects are reviewed. Lastly, some perspectives and prospects of remaining research challenges and potential pathways for practical utilization of interconnects in wearables are laid out.

Research on Energy Management of a Virtual Power Plant Based on the Improved Cooperative Particle Swarm Optimization Algorithm

Energy management of virtual power plants (VPPs) directly affects operators’ operating profits and is also related to users’ comfort and economy. In order to provide a reasonable scheme for scheduling each unit of the VPP and to improve the operating profits of the VPP, this study focuses on the optimization of VPP energy management under the premise of ensuring the comfort of flexible load users. First, flexible loads are divided into time-shiftable load (TL), power-variable load (PL), and interruptible load (IL), and their accurate power consumption models are established, respectively. Then, aiming at maximizing the operation profits of a VPP operator, an optimization model of VPP energy management considering user comfort is proposed. Finally, the improved cooperative particle swarm optimization (ICPSO) algorithm is applied to solve the proposed VPP energy management optimization model, and the optimal scheduling scheme of VPP energy management is obtained. Taking a VPP in the coastal area of China as an example, results show that the optimization model proposed in this article has the advantages of good economy and higher user comfort. Meanwhile, the ICPSO algorithm has the characteristics of faster optimization speed and higher accuracy when solving the problem with multiple variables.

Machine Learning Methods in Smart Lighting Toward Achieving User Comfort: A Survey

Smart lighting has become a universal smart product solution, with global revenues of up to US <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 5.9 billion by 2021. Six main factors drive the technology: light-emitting diode (LED) lighting, sensors, control, analytics, and intelligence. The Internet of things (IoT) concept with the end device, platform, and application layer plays an essential role in optimizing the advantages of LED lighting in the emergence of smart lighting. The ultimate aim of smart lighting research is to introduce low energy efficiency and high user comfort, where the latter is still in the infancy stage. This paper presents a systematic literature review (SLR) from a bird’s eye view covering full-length research topics on smart lighting, including issues, implementation targets, technological solutions, and prospects. In addition to that, this paper also provides a detailed and extensive overview of emerging machine learning techniques as a key solution to overcome complex problems in smart lighting. A comprehensive review of improving user comfort is also presented, such as the methodology and taxonomy of activity recognition as a promising solution and user comfort metrics, including light utilization ratio, unmet comfort ratio, light to comfort ratio, power reduction rate, flickering perception, Kruithof’s comfort curve, correlated color temperature, and relative mean square error. Finally, we discuss in-depth open issues and future challenges in increasing user comfort in smart lighting using activity recognition.

Wearable Multiple Modality Bio-Signal Recording and Processing on Chip: A Review

Remote home monitoring via wearables is rapidly gaining popularity, thanks to ever more complex vital signs recording and data analytics that are embedded into single devices. True system-on-chips (SoCs) push the envelope of power and form factor, while wearables are becoming more common-place, novel health sensing paradigms appear. Non-contact sensing technologies enable vital signs sensing without requiring any physical contact with the human body. This article reviews existing multiple-modality bio-signal recording and processing SoCs, circuit techniques for individual bio-signal readout channels including electrocardiography (ECG), Electroencephalography (EEG), Bio-impedance (BioZ), photoplethysmography (PPG), and non-contact sensing with high user comfort. The state-of-the-art wearable sensor interfaces and systems together with future development trends are provided.

Wearable radio-frequency sensing of respiratory rate, respiratory volume, and heart rate

Many health diagnostic systems demand noninvasive sensing of respiratory rate, respiratory volume, and heart rate with high user comfort. Previous methods often require multiple sensors, including skin-touch electrodes, tension belts, or nearby off-the-body readers, and hence are uncomfortable or inconvenient. This paper presents an over-clothing wearable radio-frequency sensor study, conducted on 20 healthy participants (14 females) performing voluntary breathing exercises in various postures. Two prototype sensors were placed on the participants, one close to the heart and the other below the xiphoid process to couple to the motion from heart, lungs and diaphragm, by the near-field coherent sensing principle. We can achieve a satisfactory correlation of our sensor with the reference devices for the three vital signs: heart rate (r = 0.95), respiratory rate (r = 0.93) and respiratory volume (r = 0.84). We also detected voluntary breath-hold periods with an accuracy of 96%. Further, the participants performed a breathing exercise by contracting abdomen inwards while holding breath, leading to paradoxical outward thorax motion under the isovolumetric condition, which was detected with an accuracy of 83%.

Motion Artifact Reduction for Wrist-Worn Photoplethysmograph Sensors Based on Different Wavelengths

Long-term heart rate (HR) monitoring by wrist-worn photoplethysmograph (PPG) sensors enables the assessment of health conditions during daily life with high user comfort. However, PPG signals are vulnerable to motion artifacts (MAs), which significantly affect the accuracy of estimated physiological parameters such as HR. This paper proposes a novel modular algorithm framework for MA removal based on different wavelengths for wrist-worn PPG sensors. The framework uses a green PPG signal for HR monitoring and an infrared PPG signal as the motion reference. The proposed framework includes four main steps: motion detection, motion removal using continuous wavelet transform, approximate HR estimation and signal reconstruction. The proposed algorithm is evaluated against an electrocardiogram (ECG) in terms of HR error for a dataset of 6 healthy subjects performing 21 types of motion. The proposed MA removal method reduced the average error in HR estimation from 4.3, 3.0 and 3.8 bpm to 0.6, 1.0 and 2.1 bpm in periodic, random, and continuous non-periodic motion situations, respectively.

Noise Model of Capacitive and Textile Capacitive Noncontact Electrodes for Bioelectric Applications.

In this paper, a comprehensive model for the electronic noise properties and frequency-dependent responses of printed circuit board (PCB)-based as well as textile noncontact capacitive electrodes is presented. For bioelectric diagnostics, noncontact capacitive electrodes provide an interesting alternative to classical galvanically coupled electrodes, since such a low-cost diagnostic system can be applied without preparation time and in mobile wireless environments. For even higher user comfort, textile capacitive electrodes are preferable. This paper provides a thorough study of the influence of the electrical components of capacitive electrodes and textile capacitive electrodes, as well as their surface area and circumferences on the resulting noise properties of the electrode by independently measuring the corresponding noise spectra. Consequently, the equivalent noise model is developed. The most important noise source is the high input bias resistance, which, in combination with the involved capacitance, results in an apparent $1/f^2$-power noise spectrum. By comparing the noise measurements with the noise model of the electrode, we conclude that the surface of the electrode contributes to an additional $1/f$ -power noise in the noise spectrum. We also found that the highest possible coupling capacitance is most favorable for low-noise behavior. Therefore, electrodes with electrically conducting fabric surfaces are investigated. Due to this, it is possible to enlarge the surface of the electrode and maintain a small distance between the body and the surface of the electrode. We show that with the use of textile capacitive electrodes, it is possible to reduce the noise characteristics considerably. Our findings in this paper provide a necessary source for further optimization of capacitive electrodes for bioelectric measurement applications.

Stimuli design for SSVEP-based brain computer-interface

Abstract The paper presents a process of stimuli design for SSVEP-based brain computer-interface. A brain computer-interface can be used in direct communication between a brain and a computer, without using muscles. This device is useful for paralyzed people to communicate with the surrounding environment. Design process should provide high accuracy recognition of presented stimuli and high user comfort. It is widely known how to make stimuli for BCI which are using high-grade EEG. Over recent years cheaper EEGs are becoming more and more popular, for example OpenBCI, which uses ADS1299 amplifier. In this article we review past works of other authors and compare it with our results, obtained using EEG mentioned before. We try to confirm that it is possible to use successfully OpenBCI in BCI projects.

Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording.

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only ∼10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes.

Impact of sustainable office buildings on occupant's comfort and productivity

PurposeThe purpose of this paper is to research the impact of sustainable office buildings on occupant's comfort and self‐assessed performance and work engagement.Design/methodology/approachThe research consists in an empirical study of 18 office buildings and is based on survey data from almost 1,500 employees.FindingsThe study shows that the building itself has a clear impact on the comfort level of the building user. Also, the positive impact of certain features, such as operable windows and the absence of air conditioning, can be clearly identified. While productivity is not directly correlated to comfort levels, work engagement is. Generally, the analysis shows that specific building aspects seem to have an influence on user comfort and with that, also an impact on productivity; however, this impact appears to be limited.Originality/valueThis is a very important insight since this shows the connection between employee and company and thus demonstrates that a high user comfort can reduce the turnover rate of employees. Therefore, additional planning towards user comfort and social sustainability can be shown to yield real returns.