Special Issue "Implantable Microsystems"

A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (30 June 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Kenichi Takahata

Department of Electrical & Computer Engineering, Faculty of Applied Science, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada
E-Mail
Interests: MEMS; micro sesnors and actuators; biomedical microdevices; intelligent implants; wireless microsystems; micro/nanofabrication

Special Issue Information

Dear Colleagues,

Rapid advances in medical technologies are revolutionizing the way we fight disease. Microsystems with embedded sensors and actuators have an enormous potential to play a key role in this trend. This is especially true for implant applications, in which miniaturization is the compelling need. Implantable microsystems, or “smart” micro implants, are emerging to offer a variety of innovative functions to monitor and treat localized lesions inside the body directly and more effectively via their minimally invasive forms. These devices could be implanted with minor surgeries or non-surgical procedures, such as catheterizations and even injections, and wirelessly linked to an external network (e.g., body area network) to enable pinpoint, continuous diagnosis and therapy. Their significant potential also extends to animal applications. For example, such micro implants could uniquely allow probing and/or stimulation of small animal models with virtually no impact on their physiology or mobility, thereby realizing novel ways of in vivo studies using the models.

This Special Issue is aimed to focus onto these exciting and promising technology areas. We invite original research papers, short communications, and review articles in all areas concerning implantable microsystems/MEMS and related enabling technologies, targeted at in vivo applications for human, as well as for animals.

 

Prof. Dr. Kenichi Takahata
Guest Editor


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 1200 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

  • implantable microsystems/MEMS
  • biosensors
  • visual and auditory prostheses
  • in vivo microactuators
  • implantable microfluidics
  • local drug delivery
  • biofluid manipulation
  • neural stimulation and recording
  • bioenergy harvesting
  • wireless power transfer
  • in vivo antennae and RF communication
  • biodegradable implants
  • implantable designs and micro/nanofabrication
  • biocompatible packaging

Published Papers (8 papers)

View options order results:
result details:
Displaying articles 1-8
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Continuously Operating Biosensor and Its Integration into a Hermetically Sealed Medical Implant
Micromachines 2016, 7(10), 183; https://doi.org/10.3390/mi7100183
Received: 28 June 2016 / Revised: 23 September 2016 / Accepted: 28 September 2016 / Published: 9 October 2016
Cited by 1 | PDF Full-text (2057 KB) | HTML Full-text | XML Full-text
Abstract
An integration concept for an implantable biosensor for the continuous monitoring of blood sugar levels is presented. The system architecture is based on technical modules used in cardiovascular implants in order to minimize legal certification efforts for its perspective usage in medical applications.
[...] Read more.
An integration concept for an implantable biosensor for the continuous monitoring of blood sugar levels is presented. The system architecture is based on technical modules used in cardiovascular implants in order to minimize legal certification efforts for its perspective usage in medical applications. The sensor chip operates via the principle of affinity viscometry, which is realized by a fully embedded biomedical microelectromechanical systems (BioMEMS) prepared in 0.25-µm complementary metal–oxide–semiconductor (CMOS)/BiCMOS technology. Communication with a base station is established in the 402–405 MHz band used for medical implant communication services (MICS). The implant shall operate within the interstitial tissue, and the hermetical sealing of the electronic system against interaction with the body fluid is established using titanium housing. Only the sensor chip and the antenna are encapsulated in an epoxy header closely connected to the metallic housing. The study demonstrates that biosensor implants for the sensing of low-molecular-weight metabolites in the interstitial may successfully rely on components already established in cardiovascular implantology. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Figure 1

Open AccessArticle Direct Growth of Carbon Nanotubes on New High-Density 3D Pyramid-Shaped Microelectrode Arrays for Brain-Machine Interfaces
Micromachines 2016, 7(9), 163; https://doi.org/10.3390/mi7090163
Received: 7 June 2016 / Revised: 26 August 2016 / Accepted: 30 August 2016 / Published: 8 September 2016
Cited by 2 | PDF Full-text (6284 KB) | HTML Full-text | XML Full-text
Abstract
Silicon micromachined, high-density, pyramid-shaped neural microelectrode arrays (MEAs) have been designed and fabricated for intracortical 3D recording and stimulation. The novel architecture of this MEA has made it unique among the currently available micromachined electrode arrays, as it has provided higher density contacts
[...] Read more.
Silicon micromachined, high-density, pyramid-shaped neural microelectrode arrays (MEAs) have been designed and fabricated for intracortical 3D recording and stimulation. The novel architecture of this MEA has made it unique among the currently available micromachined electrode arrays, as it has provided higher density contacts between the electrodes and targeted neural tissue facilitating recording from different depths of the brain. Our novel masking technique enhances uniform tip-exposure for variable-height electrodes and improves process time and cost significantly. The tips of the electrodes have been coated with platinum (Pt). We have reported for the first time a selective direct growth of carbon nanotubes (CNTs) on the tips of 3D MEAs using the Pt coating as a catalyzer. The average impedance of the CNT-coated electrodes at 1 kHz is 14 kΩ. The CNT coating led to a 5-fold decrease of the impedance and a 600-fold increase in charge transfer compared with the Pt electrode. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Graphical abstract

Open AccessArticle Fabrication and Microassembly of a mm-Sized Floating Probe for a Distributed Wireless Neural Interface
Micromachines 2016, 7(9), 154; https://doi.org/10.3390/mi7090154
Received: 2 July 2016 / Revised: 15 August 2016 / Accepted: 22 August 2016 / Published: 1 September 2016
Cited by 9 | PDF Full-text (4618 KB) | HTML Full-text | XML Full-text
Abstract
A new class of wireless neural interfaces is under development in the form of tens to hundreds of mm-sized untethered implants, distributed across the target brain region(s). Unlike traditional interfaces that are tethered to a centralized control unit and suffer from micromotions that
[...] Read more.
A new class of wireless neural interfaces is under development in the form of tens to hundreds of mm-sized untethered implants, distributed across the target brain region(s). Unlike traditional interfaces that are tethered to a centralized control unit and suffer from micromotions that may damage the surrounding neural tissue, the new free-floating wireless implantable neural recording (FF-WINeR) probes will be stand-alone, directly communicating with an external interrogator. Towards development of the FF-WINeR, in this paper we describe the micromachining, microassembly, and hermetic packaging of 1-mm3 passive probes, each of which consists of a thinned micromachined silicon die with a centered Ø(diameter) 130 μm through-hole, an Ø81 μm sharpened tungsten electrode, a 7-turn gold wire-wound coil wrapped around the die, two 0201 surface mount capacitors on the die, and parylene-C/Polydimethylsiloxane (PDMS) coating. The fabricated passive probe is tested under a 3-coil inductive link to evaluate power transfer efficiency (PTE) and power delivered to a load (PDL) for feasibility assessment. The minimum PTE/PDL at 137 MHz were 0.76%/240 μW and 0.6%/191 μW in the air and lamb head medium, respectively, with coil separation of 2.8 cm and 9 kΩ receiver (Rx) loading. Six hermetically sealed probes went through wireless hermeticity testing, using a 2-coil inductive link under accelerated lifetime testing condition of 85 °C, 1 atm, and 100%RH. The mean-time-to-failure (MTTF) of the probes at 37 °C is extrapolated to be 28.7 years, which is over their lifetime. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Graphical abstract

Open AccessArticle An Implantable Intravascular Pressure Sensor for a Ventricular Assist Device
Micromachines 2016, 7(8), 135; https://doi.org/10.3390/mi7080135
Received: 16 June 2016 / Revised: 4 July 2016 / Accepted: 29 July 2016 / Published: 8 August 2016
Cited by 9 | PDF Full-text (7744 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study is to investigate the intravascular application of a micro-electro-mechanical system (MEMS) pressure sensor to directly measure the hemodynamic characteristics of a ventricular assist device (VAD). A bio- and hemo-compatible packaging strategy is implemented, based on a ceramic thick
[...] Read more.
The aim of this study is to investigate the intravascular application of a micro-electro-mechanical system (MEMS) pressure sensor to directly measure the hemodynamic characteristics of a ventricular assist device (VAD). A bio- and hemo-compatible packaging strategy is implemented, based on a ceramic thick film process. A commercial sub-millimeter piezoresistive sensor is attached to an alumina substrate, and a double coating of polydimethylsiloxane (PDMS) and parylene-C is applied. The final size of the packaged device is 2.6 mm by 3.6 mm by 1.8 mm. A prototype electronic circuit for conditioning and read-out of the pressure signal is developed, satisfying the VAD-specific requirements of low power consumption (less than 14.5 mW in continuous mode) and small form factor. The packaged sensor has been submitted to extensive in vitro tests. The device displayed a temperature-independent sensitivity (12 μ V/V/mmHg) and good in vitro stability when exposed to the continuous flow of saline solution (less than 0.05 mmHg/day drift after 50 h). During in vivo validation, the transducer has been successfully used to record the arterial pressure waveform of a female sheep. A small, intravascular sensor to continuously register the blood pressure at the inflow and the outflow of a VAD is developed and successfully validated in vivo. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Graphical abstract

Open AccessArticle Towards an Implantable, Low Flow Micropump That Uses No Power in the Blocked-Flow State
Micromachines 2016, 7(6), 99; https://doi.org/10.3390/mi7060099
Received: 29 February 2016 / Revised: 26 April 2016 / Accepted: 20 May 2016 / Published: 1 June 2016
Cited by 5 | PDF Full-text (9032 KB) | HTML Full-text | XML Full-text
Abstract
Low flow rate micropumps play an increasingly important role in drug therapy research. Infusions to small biological structures and lab-on-a-chip applications require ultra-low flow rates and will benefit from the ability to expend no power in the blocked-flow state. Here we present a
[...] Read more.
Low flow rate micropumps play an increasingly important role in drug therapy research. Infusions to small biological structures and lab-on-a-chip applications require ultra-low flow rates and will benefit from the ability to expend no power in the blocked-flow state. Here we present a planar micropump based on gallium phase-change actuation that leverages expansion during solidification to occlude the flow channel in the off-power state. The presented four chamber peristaltic micropump was fabricated with a combination of Micro Electro Mechanical System (MEMS) techniques and additive manufacturing direct write technologies. The device is 7 mm × 13 mm × 1 mm (<100 mm3) with the flow channel and exterior coated with biocompatible Parylene-C, critical for implantable applications. Controllable pump rates from 18 to 104 nL/min were demonstrated, with 11.1 ± 0.35 nL pumped per actuation at an efficiency of 11 mJ/nL. The normally-closed state of the gallium actuator prevents flow and diffusion between the pump and the biological system or lab-on-a-chip, without consuming power. This is especially important for implanted applications with periodic drug delivery regimens. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Figure 1

Open AccessArticle Three-Dimensional Force Measurements During Rapid Palatal Expansion in Sus scrofa
Micromachines 2016, 7(4), 64; https://doi.org/10.3390/mi7040064
Received: 15 January 2016 / Revised: 16 March 2016 / Accepted: 6 April 2016 / Published: 12 April 2016
Cited by 1 | PDF Full-text (1943 KB) | HTML Full-text | XML Full-text
Abstract
Rapid palatal expansion is an orthodontic procedure widely used to correct the maxillary arch. However, its outcome is significantly influenced by factors that show a high degree of variability amongst patients. The traditional treatment methodology is based on an intuitive and heuristic treatment
[...] Read more.
Rapid palatal expansion is an orthodontic procedure widely used to correct the maxillary arch. However, its outcome is significantly influenced by factors that show a high degree of variability amongst patients. The traditional treatment methodology is based on an intuitive and heuristic treatment approach because the forces applied in the three dimensions are indeterminate. To enable optimal and individualized treatment, it is essential to measure the three-dimensional (3D) forces and displacements created by the expander. This paper proposes a method for performing these 3D measurements using a single embedded strain sensor, combining experimental measurements of strain in the palatal expander with 3D finite element analysis (FEA). The method is demonstrated using the maxillary jaw from a freshly euthanized pig (Sus scrofa) and a hyrax-design rapid palatal expander (RPE) appliance with integrated strain gage. The strain gage measurements are recorded using a computer interface, following which the expansion forces and extent of expansion are estimated by FEA. A total activation of 2.0 mm results in peak total force of about 100 N—almost entirely along the direction of expansion. The results also indicate that more than 85% of the input activation is immediately transferred to the palate and/or teeth. These studies demonstrate a method for assessing and individualizing expansion magnitudes and forces during orthopedic expansion of the maxilla. This provides the basis for further development of smart orthodontic appliances that provide real-time readouts of forces and movements, which will allow personalized, optimal treatment. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Figure 1

Review

Jump to: Research

Open AccessReview Flexible, Penetrating Brain Probes Enabled by Advances in Polymer Microfabrication
Micromachines 2016, 7(10), 180; https://doi.org/10.3390/mi7100180
Received: 23 July 2016 / Accepted: 19 September 2016 / Published: 4 October 2016
Cited by 11 | PDF Full-text (2816 KB) | HTML Full-text | XML Full-text
Abstract
The acquisition of high-fidelity, long-term neural recordings in vivo is critically important to advance neuroscience and brain–machine interfaces. For decades, rigid materials such as metal microwires and micromachined silicon shanks were used as invasive electrophysiological interfaces to neurons, providing either single or multiple
[...] Read more.
The acquisition of high-fidelity, long-term neural recordings in vivo is critically important to advance neuroscience and brain–machine interfaces. For decades, rigid materials such as metal microwires and micromachined silicon shanks were used as invasive electrophysiological interfaces to neurons, providing either single or multiple electrode recording sites. Extensive research has revealed that such rigid interfaces suffer from gradual recording quality degradation, in part stemming from tissue damage and the ensuing immune response arising from mechanical mismatch between the probe and brain. The development of “soft” neural probes constructed from polymer shanks has been enabled by advancements in microfabrication; this alternative has the potential to mitigate mismatch-related side effects and thus improve the quality of recordings. This review examines soft neural probe materials and their associated microfabrication techniques, the resulting soft neural probes, and their implementation including custom implantation and electrical packaging strategies. The use of soft materials necessitates careful consideration of surgical placement, often requiring the use of additional surgical shuttles or biodegradable coatings that impart temporary stiffness. Investigation of surgical implantation mechanics and histological evidence to support the use of soft probes will be presented. The review concludes with a critical discussion of the remaining technical challenges and future outlook. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Figure 1

Open AccessReview Neural Probes for Chronic Applications
Micromachines 2016, 7(10), 179; https://doi.org/10.3390/mi7100179
Received: 9 July 2016 / Revised: 12 September 2016 / Accepted: 26 September 2016 / Published: 2 October 2016
Cited by 7 | PDF Full-text (8068 KB) | HTML Full-text | XML Full-text
Abstract
Developed over approximately half a century, neural probe technology is now a mature technology in terms of its fabrication technology and serves as a practical alternative to the traditional microwires for extracellular recording. Through extensive exploration of fabrication methods, structural shapes, materials, and
[...] Read more.
Developed over approximately half a century, neural probe technology is now a mature technology in terms of its fabrication technology and serves as a practical alternative to the traditional microwires for extracellular recording. Through extensive exploration of fabrication methods, structural shapes, materials, and stimulation functionalities, neural probes are now denser, more functional and reliable. Thus, applications of neural probes are not limited to extracellular recording, brain-machine interface, and deep brain stimulation, but also include a wide range of new applications such as brain mapping, restoration of neuronal functions, and investigation of brain disorders. However, the biggest limitation of the current neural probe technology is chronic reliability; neural probes that record with high fidelity in acute settings often fail to function reliably in chronic settings. While chronic viability is imperative for both clinical uses and animal experiments, achieving one is a major technological challenge due to the chronic foreign body response to the implant. Thus, this review aims to outline the factors that potentially affect chronic recording in chronological order of implantation, summarize the methods proposed to minimize each factor, and provide a performance comparison of the neural probes developed for chronic applications. Full article
(This article belongs to the Special Issue Implantable Microsystems)
Figures

Figure 1

Back to Top