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12 pages, 3659 KiB

Open AccessArticle

Degradation Study of Thin-Film Silicon Structures in a Cell Culture Medium

by Huachun Wang, Jingjing Tian, Bingwei Lu, Yang Xie, Pengcheng Sun, Lan Yin, Yuguang Wang and Xing Sheng

Sensors 2022, 22(3), 802; https://0-doi-org.brum.beds.ac.uk/10.3390/s22030802 - 21 Jan 2022

Cited by 2 | Viewed by 1792

Abstract

Thin-film silicon (Si)-based transient electronics represents an emerging technology that enables spontaneous dissolution, absorption and, finally, physical disappearance in a controlled manner under physiological conditions, and has attracted increasing attention in pertinent clinical applications such as biomedical implants for on-body sensing, disease diagnostics, [...] Read more.

Thin-film silicon (Si)-based transient electronics represents an emerging technology that enables spontaneous dissolution, absorption and, finally, physical disappearance in a controlled manner under physiological conditions, and has attracted increasing attention in pertinent clinical applications such as biomedical implants for on-body sensing, disease diagnostics, and therapeutics. The degradation behavior of thin-film Si materials and devices is critically dependent on the device structure as well as the environment. In this work, we experimentally investigated the dissolution of planar Si thin films and micropatterned Si pillar arrays in a cell culture medium, and systematically analyzed the evolution of their topographical, physical, and chemical properties during the hydrolysis. We discovered that the cell culture medium significantly accelerates the degradation process, and Si pillar arrays present more prominent degradation effects by creating rougher surfaces, complicating surface states, and decreasing the electrochemical impedance. Additionally, the dissolution process leads to greatly reduced mechanical strength. Finally, in vitro cell culture studies demonstrate desirable biocompatibility of corroded Si pillars. The results provide a guideline for the use of thin-film Si materials and devices as transient implants in biomedicine. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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12 pages, 3553 KiB

Open AccessArticle

Printed Transformable Liquid-Metal Metamaterials and Their Application in Biomedical Sensing

by Yi Ren, Minghui Duan, Rui Guo and Jing Liu

Sensors 2021, 21(19), 6329; https://0-doi-org.brum.beds.ac.uk/10.3390/s21196329 - 22 Sep 2021

Cited by 3 | Viewed by 2291

Abstract

Metamaterial is becoming increasingly important owing to its unique physical properties and breakthrough applications. So far, most metamaterials that have been developed are made of rigid materials and structures, which may restrict their practical adaptation performances. Recently, with the further development of liquid [...] Read more.

Metamaterial is becoming increasingly important owing to its unique physical properties and breakthrough applications. So far, most metamaterials that have been developed are made of rigid materials and structures, which may restrict their practical adaptation performances. Recently, with the further development of liquid metal, some efforts have explored metamaterials based on such tunable electronic inks. Liquid metal has high flexibility and good electrical conductivity, which provides more possibilities for transformable metamaterials. Here, we developed a new flexible liquid-metal metamaterial that is highly reconfigurable and could significantly extend the working limit facing current devices. The printed electronics method was adopted to fabricate artificial units and then construct various potential transformable metamaterials. Based on metamaterial theory and printing technology, typical structured flexible liquid-metal electromagnetic metamaterials were designed and fabricated. The electronic and magnetic characteristics of the liquid-metal-based electromagnetic metamaterials were evaluated through simulated analysis and experimental measurement. Particularly, the potential of liquid-metal metamaterials in biomedical sensing was investigated. Further, the future outlook of liquid-metal metamaterials and their application in diverse categories were prospected. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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17 pages, 8073 KiB

Open AccessArticle

A Soft Haptic Glove Actuated with Shape Memory Alloy and Flexible Stretch Sensors

by Silvia Terrile, Jesus Miguelañez and Antonio Barrientos

Sensors 2021, 21(16), 5278; https://0-doi-org.brum.beds.ac.uk/10.3390/s21165278 - 04 Aug 2021

Cited by 11 | Viewed by 3231

Abstract

Haptic technology allows us to experience tactile and force sensations without the need to expose ourselves to specific environments. It also allows a more immersive experience with virtual reality devices. This paper presents the development of a soft haptic glove for kinesthetic perception. [...] Read more.

Haptic technology allows us to experience tactile and force sensations without the need to expose ourselves to specific environments. It also allows a more immersive experience with virtual reality devices. This paper presents the development of a soft haptic glove for kinesthetic perception. It is lightweight and soft to allow for a more natural hand movement. This prototype actuates two fingers with two shape memory alloy (SMA) springs. Finite element (FE) simulations of the spring have been carried out to set the dimensions of the actuators. Flexible stretch sensors provide feedback to the system to calculate the tension of the cables attached to the fingers. The control can generate several recognizable levels of force for any hand position since the objects to be picked up can vary in weight and dimension. The glove can generate three levels of force (100, 200 and 300 g) to evaluate more easily the proper functioning. We realized tests on 15 volunteers simulating forces in various order after a quick training. We also asked volunteers about the experience for comfort, global experience and simplicity). Results were satisfactory in both aspects: the glove fulfilled its function, and the users were comfortable with it. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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18 pages, 4960 KiB

Open AccessArticle

Flexible Multiscale Pore Hybrid Self-Powered Sensor for Heart Sound Detection

by Boyan Liu, Liuyang Han, Lyuming Pan, Hongzheng Li, Jingjing Zhao, Ying Dong and Xiaohao Wang

Sensors 2021, 21(13), 4508; https://doi.org/10.3390/s21134508 - 30 Jun 2021

Cited by 14 | Viewed by 3318

Abstract

This research introduces an idea of producing both nanoscale and microscale pores in piezoelectric material, and combining the properties of the molecular β-phase dipoles in ferroelectric material and the space charge dipoles in order to increase the sensitivity of the sensor and modulate [...] Read more.

This research introduces an idea of producing both nanoscale and microscale pores in piezoelectric material, and combining the properties of the molecular β-phase dipoles in ferroelectric material and the space charge dipoles in order to increase the sensitivity of the sensor and modulate the response frequency bandwidth of the material. Based on this idea, a bi-nano-micro porous dual ferro-electret hybrid self-powered flexible heart sound detection sensor is proposed. Acid etching and electrospinning were the fabrication processes used to produce a piezoelectric film with nanoscale and microscale pores, and corona poling was used for air ionization to produce an electret effect. In this paper, the manufacturing process of the sensor is introduced, and the effect of the porous structure and corona poling on improving the performance of the sensor is discussed. The proposed flexible sensor has an equivalent piezoelectric coefficient d₃₃ of 3312 pC/N, which is much larger than the piezoelectric coefficient of the common piezoelectric materials. Experiments were carried out to verify the function of the flexible sensor together with the SS17L heart sound sensor (BIOPAC, Goleta, CA, USA) as a reference. The test results demonstrated its practical application for wearable heart sound detection and the potential for heart disease detection. The proposed flexible sensor in this paper could realize batch production, and has the advantages of flexibility, low production cost and a short processing time compared with the existing heart sound detection sensors. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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12 pages, 2503 KiB

Open AccessArticle

A Polymeric Bilayer Multi-Legged Soft Millirobot with Dual Actuation and Humidity Sensing

by Shidai Tian, Shijie Li, Yijie Hu, Wei Wang, Aifang Yu, Lingyu Wan and Junyi Zhai

Sensors 2021, 21(6), 1972; https://0-doi-org.brum.beds.ac.uk/10.3390/s21061972 - 11 Mar 2021

Cited by 6 | Viewed by 2646

Abstract

There are numerous works that report wirelessly controlling the locomotion of soft robots through a single actuation method of light or magnetism. However, coupling multiple driving modes to improve the mobility of robots is still in its infancy. Here, we present a soft [...] Read more.

There are numerous works that report wirelessly controlling the locomotion of soft robots through a single actuation method of light or magnetism. However, coupling multiple driving modes to improve the mobility of robots is still in its infancy. Here, we present a soft multi-legged millirobot that can move, climb a slope, swim and detect a signal by near-infrared irradiation (NIR) light or magnetic field dual actuation. Due to the design of the feet structure, our soft millirobot incorporates the advantages of a single actuation mode of light or magnetism. Furthermore, it can execute a compulsory exercise to sense a signal and analyze the ambience fluctuation in a narrow place. This work provides a novel alternative for soft robots to achieve multimode actuation and signal sensing. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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19 pages, 6874 KiB

Open AccessEditor’s ChoiceReview

Recent Progress in Self-Powered Sensors Based on Triboelectric Nanogenerators

by Junpeng Wu, Yang Zheng and Xiaoyi Li

Sensors 2021, 21(21), 7129; https://0-doi-org.brum.beds.ac.uk/10.3390/s21217129 - 27 Oct 2021

Cited by 33 | Viewed by 4506

Abstract

The emergence of the Internet of Things (IoT) has subverted people’s lives, causing the rapid development of sensor technologies. However, traditional sensor energy sources, like batteries, suffer from the pollution problem and the limited lifetime for powering widely implemented electronics or sensors. Therefore, [...] Read more.

The emergence of the Internet of Things (IoT) has subverted people’s lives, causing the rapid development of sensor technologies. However, traditional sensor energy sources, like batteries, suffer from the pollution problem and the limited lifetime for powering widely implemented electronics or sensors. Therefore, it is essential to obtain self-powered sensors integrated with renewable energy harvesters. The triboelectric nanogenerator (TENG), which can convert the surrounding mechanical energy into electrical energy based on the surface triboelectrification effect, was born of this background. This paper systematically introduces the working principle of the TENG-based self-powered sensor, including the triboelectrification effect, Maxwell’s displacement current, and quantitative analysis method. Meanwhile, this paper also reviews the recent application of TENG in different fields and summarizes the future development and current problems of TENG. We believe that there will be a rise of TENG-based self-powered sensors in the future. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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22 pages, 3128 KiB

Open AccessReview

Progress in ZnO Nanosensors

by Miaoling Que, Chong Lin, Jiawei Sun, Lixiang Chen, Xiaohong Sun and Yunfei Sun

Sensors 2021, 21(16), 5502; https://0-doi-org.brum.beds.ac.uk/10.3390/s21165502 - 16 Aug 2021

Cited by 41 | Viewed by 5891

Abstract

Developing various nanosensors with superior performance for accurate and sensitive detection of some physical signals is essential for advances in electronic systems. Zinc oxide (ZnO) is a unique semiconductor material with wide bandgap (3.37 eV) and high exciton binding energy (60 meV) at [...] Read more.

Developing various nanosensors with superior performance for accurate and sensitive detection of some physical signals is essential for advances in electronic systems. Zinc oxide (ZnO) is a unique semiconductor material with wide bandgap (3.37 eV) and high exciton binding energy (60 meV) at room temperature. ZnO nanostructures have been investigated extensively for possible use as high-performance sensors, due to their excellent optical, piezoelectric and electrochemical properties, as well as the large surface area. In this review, we primarily introduce the morphology and major synthetic methods of ZnO nanomaterials, with a brief discussion of the advantages and weaknesses of each method. Then, we mainly focus on the recent progress in ZnO nanosensors according to the functional classification, including pressure sensor, gas sensor, photoelectric sensor, biosensor and temperature sensor. We provide a comprehensive analysis of the research status and constraints for the development of ZnO nanosensor in each category. Finally, the challenges and future research directions of nanosensors based on ZnO are prospected and summarized. It is of profound significance to research ZnO nanosensors in depth, which will promote the development of artificial intelligence, medical and health, as well as industrial, production. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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21 pages, 4235 KiB

Open AccessReview

Recent Advances in Flexible Tactile Sensors for Intelligent Systems

by Yiyao Peng, Ning Yang, Qian Xu, Yang Dai and Zhiqiang Wang

Sensors 2021, 21(16), 5392; https://0-doi-org.brum.beds.ac.uk/10.3390/s21165392 - 10 Aug 2021

Cited by 51 | Viewed by 8125

Abstract

Tactile sensors are an important medium for artificial intelligence systems to perceive their external environment. With the rapid development of smart robots, wearable devices, and human-computer interaction interfaces, flexible tactile sensing has attracted extensive attention. An overview of the recent development in high-performance [...] Read more.

Tactile sensors are an important medium for artificial intelligence systems to perceive their external environment. With the rapid development of smart robots, wearable devices, and human-computer interaction interfaces, flexible tactile sensing has attracted extensive attention. An overview of the recent development in high-performance tactile sensors used for smart systems is introduced. The main transduction mechanisms of flexible tactile sensors including piezoresistive, capacitive, piezoelectric, and triboelectric sensors are discussed in detail. The development status of flexible tactile sensors with high resolution, high sensitive, self-powered, and visual capabilities are focused on. Then, for intelligent systems, the wide application prospects of flexible tactile sensors in the fields of wearable electronics, intelligent robots, human-computer interaction interfaces, and implantable electronics are systematically discussed. Finally, the future prospects of flexible tactile sensors for intelligent systems are proposed. Full article

(This article belongs to the Special Issue Flexible and Stretchable Sensor Technology)

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