Special Issue "Flexible Electronics for Wearable and Implantable Health Care Applications"

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "B:Biology and Biomedicine".

Deadline for manuscript submissions: 30 June 2021.

Special Issue Editors

Dr. Hoang-Phuong Phan
E-Mail Website
Guest Editor
Queensland Micro and Nanotechnology Centre, Griffith University, Brisbane, Australia
Interests: MEMS/NEMS; piezoresistive and piezoelectric materials; sensors for harsh environments; strain engineering
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Flexible electronics have attracted great attention of interest owing to their unprecedented properties over conventional bulk-semiconductor base devices. In the last decade, the development of flexible electronics has been continuously advanced from materials, design concepts to innovative fabrication technologies. Their applications can be found in a broad range of industries including energy, medicine, and robotics. In health care and medical applications, flexible electronics offers new functionalities such as smart wears and epidermal sensors that can be directly mounted onto skin to track different biophysiological parameters from users. The capability to form conformal contacts with soft bio-tissue also opens new paradigm for implantable electronics in neurological signalling and simulating, thereby leveraging advances in disease diagnosis and treatment.

This issue seeks for review papers and technical reports on flexible electronics for health care applications. It aims to provide the readers a comprehensive and broad view on the state-of-the-art and future perspective of soft electronics for biological sensing. In particular, this issue includes but is not limit to the following topics:

  • Wearable and stretchable mechanical sensors
  • Wearable bio-chemical sensors
  • Implantable electronics
  • Biodegradable materials
  • Functional electronic materials and smart designs for stretchable electronics
  • Energy storage and harvesting technologies for soft electronics

Dr. Hoang-Phuong Phan
Prof. Nam-Trung Nguyen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Wearable and stretchable mechanical sensors
  • Wearable bio-chemical sensors
  • Implantable electronics
  • Biodegradable materials
  • Functional electronic materials and smart designs for stretchable electronics
  • Energy storage and harvesting technologies for soft electronics

Published Papers (4 papers)

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Research

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Article
Recent Developments on Modeling for a 3-DOF Micro-Hand Based on AI Methods
Micromachines 2020, 11(9), 792; https://doi.org/10.3390/mi11090792 - 21 Aug 2020
Cited by 1 | Viewed by 565
Abstract
Recently, soft actuators have been expected to have many applications in various fields. Most of the actuators are composed of flexible materials and driven by air pressure. The 3-DOF micro-hand, which is a kind of soft actuator, can realize a three degrees of [...] Read more.
Recently, soft actuators have been expected to have many applications in various fields. Most of the actuators are composed of flexible materials and driven by air pressure. The 3-DOF micro-hand, which is a kind of soft actuator, can realize a three degrees of freedom motion by changing the applied air pressure pattern. However, the input–output relation is nonlinear and complicated. In previous research, a model of the micro-hand was proposed, but an error between the model and the experimental results was large. In this paper, modeling for the micro-hand is proposed by using multi-output support vector regression (MSVR) and ant colony optimization (ACO), which is one of the artificial intelligence (AI) methods. MSVR estimates the input–output relation of the micro-hand. ACO optimizes the parameters of the MSVR model. Full article
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Article
Design and Implementation of a Multifunction Wearable Device to Monitor Sleep Physiological Signals
Micromachines 2020, 11(7), 672; https://doi.org/10.3390/mi11070672 - 10 Jul 2020
Cited by 4 | Viewed by 1055
Abstract
We present a wearable device built on an Adafruit Circuit Playground Express (CPE) board and integrated with a photoplethysmographic (PPG) optical sensor for heart rate monitoring and multiple embedded sensors for medical applications—in particular, sleep physiological signal monitoring. Our device is portable and [...] Read more.
We present a wearable device built on an Adafruit Circuit Playground Express (CPE) board and integrated with a photoplethysmographic (PPG) optical sensor for heart rate monitoring and multiple embedded sensors for medical applications—in particular, sleep physiological signal monitoring. Our device is portable and lightweight. Due to the microcontroller unit (MCU)-based architecture of the proposed device, it is scalable and flexible. Thus, with the addition of different plug-and-play sensors, it can be used in many applications in different fields. The innovation introduced in this study is that with additional sensors, we can determine whether there are intermediary variables that can be modified to improve our sleep monitoring algorithm. Additionally, although the proposed device has a relatively low cost, it achieves substantially improved performance compared to the commercially available Philips ActiWatch2 wearable device, which has been approved by the Food and Drug Administration (FDA). To assess the reliability of our device, we compared physiological sleep signals recorded simultaneously from volunteers using both our device and ActiWatch2. Motion and light detection data from our device were shown to be correlated to data simultaneously collected using the ActiWatch2, with correlation coefficients of 0.78 and 0.89, respectively. For 7 days of continuous data collection, there was only one instance of a false positive, in which our device detected a sleep interval, while the ActiWatch2 did not. The most important aspect of our research is the use of an open architecture. At the hardware level, general purpose input/output (GPIO), serial peripheral interface (SPI), integrated circuit (I2C), and universal asynchronous receiver-transmitter (UART) standards were used. At the software level, an object-oriented programming methodology was used to develop the system. Because the use of plug-and-play sensors is associated with the risk of adverse outcomes, such as system instability, this study heavily relied on object-oriented programming. Object-oriented programming improves system stability when hardware components are replaced or upgraded, allowing us to change the original system components at a low cost. Therefore, our device is easily scalable and has low commercialization costs. The proposed wearable device can facilitate the long-term tracking of physiological signals in sleep monitoring and related research. The open architecture of our device facilitates collaboration and allows other researchers to adapt our device for use in their own research, which is the main characteristic and contribution of this study. Full article
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Article
Preparing Polypyrrole-Coated Stretchable Textile via Low-Temperature Interfacial Polymerization for Highly Sensitive Strain Sensor
Micromachines 2019, 10(11), 788; https://doi.org/10.3390/mi10110788 - 17 Nov 2019
Cited by 7 | Viewed by 1270
Abstract
The stretchable sensor has been considered as the most important component in a wearable device. However, it is still a great challenge to develop a highly sensitive textile-based strain sensor with good flexibility, excellent skin affinity, and large dynamic range. Herein, polypyrrole (PPy) [...] Read more.
The stretchable sensor has been considered as the most important component in a wearable device. However, it is still a great challenge to develop a highly sensitive textile-based strain sensor with good flexibility, excellent skin affinity, and large dynamic range. Herein, polypyrrole (PPy) was immobilized on a stretchable textile knitted by polyester and spandex via low-temperature interfacial polymerization to prepare a conductive strain sensor for human motion and respiration measurements. Scanning electron microscopy, Fourier transform infrared spectrometry, and thermal gravimetric data verify that a thin layer of PPy has been successfully coated on the textile with a high density and very uniform distribution. The resistance of the as-prepared textile is 21.25 Ω/cm2 and the PPy-coated textile could be used as an electric conductor to light up a LED lamp. Moreover, the textile could tolerate folding at an angle of 180° and 500 times of bending-twisting cycles without significant changes on its resistance. A negative correlation between the resistance change and the applied strain is observed for the textile-based sensor in the strain ranging from 0 to 71% with the gauge factor of −0.46. After more than 200 cycles of stretching-releasing under the strain of 26%, there is no obvious alteration on the sensing responses. The sensors were attached on volunteers’ body or clothes for the real-time measurement of human motions and respiration, demonstrating that the textile-based sensor could sensitively detect finger, elbow, and knee bending and differentiate deep, normal, and fast breath. This work may provide an approach to uniform and dense coating conductive polymers on textiles for highly sensitive and stretchable sensors, which possess great potentials in practical applications for real-time monitoring human motions and physiological signs. Full article
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Perspective
Implanted Flexible Electronics: Set Device Lifetime with Smart Nanomaterials
Micromachines 2021, 12(2), 157; https://doi.org/10.3390/mi12020157 - 05 Feb 2021
Viewed by 644
Abstract
Flexible electronics is one of the most attractive and anticipated markets in the internet-of-things era, covering a broad range of practical and industrial applications from displays and energy harvesting to health care devices. The mechanical flexibility, combined with high performance electronics, and integrated [...] Read more.
Flexible electronics is one of the most attractive and anticipated markets in the internet-of-things era, covering a broad range of practical and industrial applications from displays and energy harvesting to health care devices. The mechanical flexibility, combined with high performance electronics, and integrated on a soft substrate offer unprecedented functionality for biomedical applications. This paper presents a brief snapshot on the materials of choice for niche flexible bio-implanted devices that address the requirements for both biodegradable and long-term operational streams. The paper also discusses potential future research directions in this rapidly growing field. Full article
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