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Implantable Sensors 2018
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Implantable Sensors 2018

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (30 September 2018) | Viewed by 58150

Special Issue Editors

Prof. Dr. Keat Ghee Ghee Ong

E-Mail Website
Guest Editor
Michigan Technological University, Department of Biomedical Engineering, Houghton, USA
Interests: implantable sensors; wireless sensors; regenerative medicine; biomedical instrumentation; magnetoelastic materials
Special Issues, Collections and Topics in MDPI journals
Dr. David Budgett

E-Mail Website
Guest Editor
University of Auckland, Auckland Bioengineering Institute, Auckland, New Zealand
Interests: implantable devices; pressure sensors; optogenetics; wireless power; encapsulation systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Sensors is inviting researchers to showcase the importance of implantable sensors in the medical field by reporting on their latest implementations in the study, treatment and prevention of various diseases and injuries. This issue is looking for the latest technological advancements, including, but not limited to, developments in sensor design, electronics, data processing, materials, longevity and power systems which will play important roles in the adoption of these sensors. In addition, methods of wireless transmission from within the human body, and solutions to the challenges faced by the implantable sensors are also of great interest. Below is a list of the focus areas for this issue.

  • Sensor design and fabrication
    • Innovative sensing technologies for in vivo monitoring
    • New fabrication techniques for implantable sensors
    • New technologies for enhancing the performance of implantable sensors
  • Wireless implantable sensors
    • New designs or developments of passive and active implantable sensors
    • Power management including energy harvesting, energy storage, wireless power and energy conservation within these sensors
  • Applications
    • Implementations of implantable sensors for treating, monitoring, or preventing of diseases and/or injuries
    • Reports and solutions for challenges such as biocompatibility issue, sensor fouling and drift, and other technical limitations of current implantable sensors
    • Applications of implantable sensors as research tools

In addition to the priority areas listed above, Sensors will also consider other findings and advancements related to implantable sensors. However, it is advisable to communicate with the Guest Editors to determine their alignment to this issue. Sensors will also accept critical reviews in the field or sub-field of implantable sensors, but prior coordination with the Guest Editors is recommended.

Dr. Keat Ghee Ong
Dr. David Budgett
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 submissions that pass pre-check are 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. Sensors is an international peer-reviewed open access semimonthly 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 2600 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.

Published Papers (10 papers)

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Research

10 pages, 3663 KiB  
Article
An Implantable Sensorized Lead for Continuous Monitoring of Cardiac Apex Rotation
by Emanuela Marcelli and Laura Cercenelli
Sensors 2018, 18(12), 4195; https://doi.org/10.3390/s18124195 - 30 Nov 2018
Cited by 2 | Viewed by 3156
Abstract
Changes in the pattern or amplitude of cardiac rotation have been associated with important cardiovascular diseases, including Heart Failure (HF) which is one of the major health problems worldwide. Recent advances in echocardiographic techniques have allowed for non-invasive quantification of cardiac rotation; however, [...] Read more.
Changes in the pattern or amplitude of cardiac rotation have been associated with important cardiovascular diseases, including Heart Failure (HF) which is one of the major health problems worldwide. Recent advances in echocardiographic techniques have allowed for non-invasive quantification of cardiac rotation; however, these examinations do not address the continuous monitoring of patient status. We have presented a newly developed implantable, transvenous lead with a tri-axis (3D) MEMS gyroscope incorporated near its tip to measure cardiac apex rotation in the three-dimensional space. We have named it CardioMon for its intended use for cardiac monitoring. If compared with currently proposed implantable systems for HF monitoring based on the use of pressure sensors that can have reliability issues, an implantable motion sensor like a gyroscope holds the premise for more reliable long term monitoring. The first prototypal assembly of the CardioMon lead has been tested to assess the reliability of the 3D gyroscope readings. In vitro results showed that the novel sensorized CardioMon lead was accurate and reliable in detecting angular velocities within the range of cardiac twisting velocities. Animal experiments will be planned to further evaluate the CardioMon lead in in vivo environments and to investigate possible endocardial implantation sites. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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11 pages, 5261 KiB  
Article
A Novel Sensorized Heart Valve Prosthesis: Preliminary In Vitro Evaluation
by Emanuela Marcelli, Barbara Bortolani, Ivan Corazza and Laura Cercenelli
Sensors 2018, 18(11), 3905; https://doi.org/10.3390/s18113905 - 13 Nov 2018
Cited by 11 | Viewed by 3227
Abstract
Background: Recent studies have shown that subclinical valve thrombosis in heart valve prosthesis (HVP) can be responsible for reduced leaflet motion detectable only by advanced imaging diagnostics. We conceived a novel sensorized HVP able to detect earlier any thrombus formation that may alter [...] Read more.
Background: Recent studies have shown that subclinical valve thrombosis in heart valve prosthesis (HVP) can be responsible for reduced leaflet motion detectable only by advanced imaging diagnostics. We conceived a novel sensorized HVP able to detect earlier any thrombus formation that may alter the leaflets motion using an electric impedance measurement, IntraValvular Impedance (IVI). Methods: For IVI measurement, dedicated electrodes are embedded in the structure of the HVP to generate a local electric field that is altered by the moving valve leaflets during their cyclic opening/closing. We present preliminary in vitro results using a first prototype of sensorized mechanical heart valve connected to an external impedance measurement system. The prototype was tested on a circulatory mock loop system and the IVI signals were recorded during both normal dynamics and experimentally induced altered working of the leaflets. Results: Recordings showed a very repetitive and stable IVI signal during the normal cyclic opening/closing of the HVP. The induced alterations in leaflet motion were reflected in the IVI signal. Conclusions: The novel sensorized HVP has great potential to give early warning of possible subclinical valve thrombosis altering the valve leaflet motion, and to help in tailoring the anticoagulation therapy. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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16 pages, 8769 KiB  
Article
Design, Modeling, and Evaluation of the Eddy Current Sensor Deeply Implanted in the Human Body
by Rajas Prakash Khokle, Karu P. Esselle and Desmond J. Bokor
Sensors 2018, 18(11), 3888; https://doi.org/10.3390/s18113888 - 11 Nov 2018
Cited by 4 | Viewed by 3012
Abstract
Joint replacement surgeries have enabled motion for millions of people suffering from arthritis or grave injuries. However, over 10% of these surgeries are revision surgeries. We have first analyzed the data from the worldwide orthopedic registers and concluded that the micromotion of orthopedic [...] Read more.
Joint replacement surgeries have enabled motion for millions of people suffering from arthritis or grave injuries. However, over 10% of these surgeries are revision surgeries. We have first analyzed the data from the worldwide orthopedic registers and concluded that the micromotion of orthopedic implants is the major reason for revisions. Then, we propose the use of inductive eddy current sensors for in vivo micromotion detection of the order of tens of μ m. To design and evaluate its characteristics, we have developed efficient strategies for the accurate numerical simulation of eddy current sensors implanted in the human body. We present the response of the eddy current sensor as a function of its frequency and position based on the robust curve fit analysis. Sensitivity and Sensitivity Range parameters are defined for the present context and are evaluated. The proposed sensors are fabricated and tested in the bovine leg. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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12 pages, 1798 KiB  
Article
Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments
by Flurin Pfiffner, Lukas Prochazka, Ivo Dobrev, Karina Klein, Patrizia Sulser, Dominik Péus, Jae Hoon Sim, Adrian Dalbert, Christof Röösli, Dominik Obrist and Alexander Huber
Sensors 2018, 18(10), 3565; https://doi.org/10.3390/s18103565 - 21 Oct 2018
Cited by 5 | Viewed by 4120
Abstract
(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute [...] Read more.
(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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12 pages, 3396 KiB  
Article
Measurement of Urinary Bladder Pressure: A Comparison of Methods
by Ingelin Clausen, Lars Geir W. Tvedt and Thomas Glott
Sensors 2018, 18(7), 2128; https://doi.org/10.3390/s18072128 - 03 Jul 2018
Cited by 11 | Viewed by 9966
Abstract
Pressure is an essential parameter for the normal function of almost all organs in the human body. Measurement of pressure is therefore highly important in clinical practice and medical research. In clinical practice, pressures are often measured indirectly through a fluid line where [...] Read more.
Pressure is an essential parameter for the normal function of almost all organs in the human body. Measurement of pressure is therefore highly important in clinical practice and medical research. In clinical practice, pressures are often measured indirectly through a fluid line where the pressure is transmitted from the organ of interest to a remote, externally localized transducer. This method has several limitations and is prone to artefacts from movements. Results from an in vitro bench study comparing the characteristics of two different sensor systems for bladder assessment are presented; a new cystometry system using a MEMS-based in-target organ sensor was compared with a conventional system using water-filled lines connected to external transducers. Robustness to measurement errors due to patient movement was investigated through response to forced vibrations. While the new cystometry system detected real changes in applied pressure for excitation frequencies ranging from 5 Hz to 25 Hz, such small and high-frequency stimuli were not transmitted through the water-filled line connected to the external transducer. The new sensor system worked well after a resilient test at frequencies up to 70 Hz. The in-target organ sensor system will offer new possibilities for long-term monitoring of in vivo pressure in general. This opens up the possibility for future personalized medical treatment and renders possible new health services and, thereby, an increased patient empowerment and quality of life. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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13 pages, 4257 KiB  
Article
Miniaturized Sensors Registering the Long-Term Course of Suture Tension In Vivo under Varying Intra-Abdominal Pressure
by Jörg Höer and Oliver Wetter
Sensors 2018, 18(6), 1729; https://doi.org/10.3390/s18061729 - 28 May 2018
Cited by 6 | Viewed by 3317
Abstract
Background: Failure of laparotomy closure develops after up to 20% of abdominal operations. Suture tension has an influence on the quality of tissue regeneration. No sensors are available to register suture tension dynamics in vivo. Methods: In a series of animal experiments, the [...] Read more.
Background: Failure of laparotomy closure develops after up to 20% of abdominal operations. Suture tension has an influence on the quality of tissue regeneration. No sensors are available to register suture tension dynamics in vivo. Methods: In a series of animal experiments, the effect of suture tension on the ultrastructure of the healing incision was examined. Surgeons’ ability to suture with target tension was tested. An implantable sensor and data logger were developed and tested experimentally in sutures closing midline laparotomies in pigs both under normal and elevated intra-abdominal pressure. Results: High suture tension has a negative influence on the regeneration of laparotomy incisions. Running sutures for laparotomy closure lose 45% of their initial tension over periods of 23 h. Intermittent elevation of intra-abdominal pressure to 30 mm Hg leads to a near total loss of suture tension after 23 h. Conclusion: Surgeons are not able to control and reproduce suture tension. Suture tension dynamics can be measured in vivo by the sensor developed. Further research is needed to define a tissue-specific suture tension optimum to reduce the incidence of complications after laparotomy. Techniques for laparotomy closure need to be modified. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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21 pages, 10398 KiB  
Article
Minimally-Invasive Neural Interface for Distributed Wireless Electrocorticogram Recording Systems
by Sun-Il Chang, Sung-Yun Park and Euisik Yoon
Sensors 2018, 18(1), 263; https://doi.org/10.3390/s18010263 - 17 Jan 2018
Cited by 11 | Viewed by 7745
Abstract
This paper presents a minimally-invasive neural interface for distributed wireless electrocorticogram (ECoG) recording systems. The proposed interface equips all necessary components for ECoG recording, such as the high performance front-end integrated circuits, a fabricated flexible microelectrode array, and wireless communication inside a miniaturized [...] Read more.
This paper presents a minimally-invasive neural interface for distributed wireless electrocorticogram (ECoG) recording systems. The proposed interface equips all necessary components for ECoG recording, such as the high performance front-end integrated circuits, a fabricated flexible microelectrode array, and wireless communication inside a miniaturized custom-made platform. The multiple units of the interface systems can be deployed to cover a broad range of the target brain region and transmit signals via a built-in intra-skin communication (ISCOM) module. The core integrated circuit (IC) consists of 16-channel, low-power push-pull double-gated preamplifiers, in-channel successive approximation register analog-to-digital converters (SAR ADC) with a single-clocked bootstrapping switch and a time-delayed control unit, an ISCOM module for wireless data transfer through the skin instead of a power-hungry RF wireless transmitter, and a monolithic voltage/current reference generator to support the aforementioned analog and mixed-signal circuit blocks. The IC was fabricated using 250 nm CMOS processes in an area of 3.2 × 0.9 mm2 and achieved the low-power operation of 2.5 µW per channel. Input-referred noise was measured as 5.62 µVrms for 10 Hz to 10 kHz and ENOB of 7.21 at 31.25 kS/s. The implemented system successfully recorded multi-channel neural activities in vivo from a primate and demonstrated modular expandability using the ISCOM with power consumption of 160 µW. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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6237 KiB  
Article
An Implantable Wireless Neural Interface System for Simultaneous Recording and Stimulation of Peripheral Nerve with a Single Cuff Electrode
by Ahnsei Shon, Jun-Uk Chu, Jiuk Jung, Hyungmin Kim and Inchan Youn
Sensors 2018, 18(1), 1; https://doi.org/10.3390/s18010001 - 21 Dec 2017
Cited by 41 | Viewed by 11968
Abstract
Recently, implantable devices have become widely used in neural prostheses because they eliminate endemic drawbacks of conventional percutaneous neural interface systems. However, there are still several issues to be considered: low-efficiency wireless power transmission; wireless data communication over restricted operating distance with high [...] Read more.
Recently, implantable devices have become widely used in neural prostheses because they eliminate endemic drawbacks of conventional percutaneous neural interface systems. However, there are still several issues to be considered: low-efficiency wireless power transmission; wireless data communication over restricted operating distance with high power consumption; and limited functionality, working either as a neural signal recorder or as a stimulator. To overcome these issues, we suggest a novel implantable wireless neural interface system for simultaneous neural signal recording and stimulation using a single cuff electrode. By using widely available commercial off-the-shelf (COTS) components, an easily reconfigurable implantable wireless neural interface system was implemented into one compact module. The implantable device includes a wireless power consortium (WPC)-compliant power transmission circuit, a medical implant communication service (MICS)-band-based radio link and a cuff-electrode path controller for simultaneous neural signal recording and stimulation. During in vivo experiments with rabbit models, the implantable device successfully recorded and stimulated the tibial and peroneal nerves while communicating with the external device. The proposed system can be modified for various implantable medical devices, especially such as closed-loop control based implantable neural prostheses requiring neural signal recording and stimulation at the same time. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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3378 KiB  
Article
Induction of Inflammation In Vivo by Electrocardiogram Sensor Operation Using Wireless Power Transmission
by Jin-Chul Heo, Beomjoon Kim, Yoon-Nyun Kim, Dae-Kwang Kim and Jong-Ha Lee
Sensors 2017, 17(12), 2905; https://doi.org/10.3390/s17122905 - 14 Dec 2017
Cited by 6 | Viewed by 4072
Abstract
Prolonged monitoring by cardiac electrocardiogram (ECG) sensors is useful for patients with emergency heart conditions. However, implant monitoring systems are limited by lack of tissue biocompatibility. Here, we developed an implantable ECG sensor for real-time monitoring of ventricular fibrillation and evaluated its biocompatibility [...] Read more.
Prolonged monitoring by cardiac electrocardiogram (ECG) sensors is useful for patients with emergency heart conditions. However, implant monitoring systems are limited by lack of tissue biocompatibility. Here, we developed an implantable ECG sensor for real-time monitoring of ventricular fibrillation and evaluated its biocompatibility using an animal model. The implantable sensor comprised transplant sensors with two electrodes, a wireless power transmission system, and a monitoring system. The sensor was inserted into the subcutaneous tissue of the abdominal area and operated for 1 h/day for 5 days using a wireless power system. Importantly, the sensor was encapsulated by subcutaneous tissue and induced angiogenesis, inflammation, and phagocytosis. In addition, we observed that the levels of inflammation-related markers increased with wireless-powered transmission via the ECG sensor; in particular, levels of the Th-1 cytokine interleukin-12 were significantly increased. The results showed that induced tissue damage was associated with the use of wireless-powered sensors. We also investigated research strategies for the prevention of adverse effects caused by lack of tissue biocompatibility of a wireless-powered ECG monitoring system and provided information on the clinical applications of inflammatory reactions in implant treatment using the wireless-powered transmission system. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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12234 KiB  
Article
Concept and Evaluation of a New Piezoelectric Transducer for an Implantable Middle Ear Hearing Device
by Houguang Liu, Jinlei Cheng, Jianhua Yang, Zhushi Rao, Gang Cheng, Shanguo Yang, Xinsheng Huang and Mengli Wang
Sensors 2017, 17(11), 2515; https://doi.org/10.3390/s17112515 - 02 Nov 2017
Cited by 18 | Viewed by 6179
Abstract
Implantable middle ear hearing devices (IMEHDs) have been developed as a new technology to overcome the limitations of conventional hearing aids. The piezoelectric cantilever transducers currently used in the IMEHDs have the advantages of low power consumption and ease of fabrication, but generate [...] Read more.
Implantable middle ear hearing devices (IMEHDs) have been developed as a new technology to overcome the limitations of conventional hearing aids. The piezoelectric cantilever transducers currently used in the IMEHDs have the advantages of low power consumption and ease of fabrication, but generate less high-frequency output. To address this problem, we proposed and designed a new piezoelectric transducer based on a piezoelectric stack for the IMEHD. This new transducer, attached to the incus body with a coupling rod, stimulates the ossicular chain in response to the expansion-and-contraction of its piezoelectric stack. To test its feasibility for hearing loss compensation, a bench testing of the transducer prototype and a temporal bone experiment were conducted, respectively. Bench testing results showed that the new transducer did have a broad frequency bandwidth. Besides, the transducer was found to have a low total harmonic distortion (<0.75%) in all frequencies, and small release time (1 ms). The temporal bone experiment further proved that the transducer has the capability to produce sufficient vibrations to compensate for severe sensorineural hearing loss, especially at high frequencies. This property benefits the treatment of the most common sloping high-frequency sensorineural hearing loss. To produce a 100 dB SPL equivalent sound pressure at 1 kHz, its power consumption is 0.49 mW, which is low enough for the transducer to be utilized in the IMEHD. Full article
(This article belongs to the Special Issue Implantable Sensors 2018)
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