Special Issue "Deformable Bioelectronics Based on Functional Micro/nanomaterials"

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D:Materials and Processing".

Deadline for manuscript submissions: closed (1 May 2020).

Special Issue Editor

Dr. Donghee Son
E-Mail Website
Guest Editor
Sungkyunkwan University, Suwon 16419, Korea
Interests: stretchable electronics; self-healing electronics; peripheral neural interface; functional nanomaterials; bio-integrated electronic system
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Deformable bioelectronics based on functional micro/nanomaterials, the topic of this Special Issue, have attracted huge attention owing to their tremendous potential in wearable and implantable applications. Specifically, high-performance functional micro/nanomaterials are able to allow the deformable electronics to be more feasible in next-generation healthcare and medicine due to their exceptional biocompatibility, flexibility, and even bioresorbability while maintaining high electrical performances. Therefore, the multifunctional deformable electronics integrated with such superior micro/nanomaterials have been expected to be comparable to conventional material-driven devices in the near future. An approach to the realization of the wearable/implantable bioelectronics can be divided into several methods: i) Using intrinsically flexible/stretchable/biocompatible conducting and semiconducting micro/nanocomposites, ii) enabling the rigid inorganic micro/nanomembranes to be deformable using the serpentine interconnect and neutral mechanical plane, iii) integrating commercial electronic chips, non-volatile memory modules, batteries, and wireless/power communication parts into flexible or transient substrates. In this Special Issue, we will cover various methodologies related to flexible/stretchable and bioresorbable micro/nanomaterial-based wearable and implantable bioelectronics. We invite researchers who are working on deformable materials and devices, ranging from biocompatible functional material synthesis and its device fabrication to process and system integration, to submit their high-quality manuscript for publication in this Special Issue.

Dr. Donghee Son
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.

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Keywords

  • Flexible electronics
  • Stretchable electronics
  • Transient electronics
  • Functional nanomaterials
  • MEMS
  • Bio-integrated electronic systems
  • Wireless communication
  • Human–machine interface
  • Bioresorbable materials
  • Biocompatibility
  • Neural interface
  • Brain
  • Spinal cord
  • Optogenetics

Published Papers (6 papers)

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Research

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Article
Stretchable and Robust Candle-Soot Nanoparticle-Polydimethylsiloxane Composite Films for Laser-Ultrasound Transmitters
Micromachines 2020, 11(7), 631; https://doi.org/10.3390/mi11070631 - 28 Jun 2020
Cited by 2 | Viewed by 888
Abstract
Considerable attention has been devoted to the development of nanomaterial-based photoacoustic transmitters for ultrasound therapy and diagnosis applications. Here, we fabricate and characterize candle-soot nanoparticles (CSNPs) and polydimethylsiloxane (PDMS) composite-based photoacoustic transmitters, based on a solution process, not just to achieve high-frequency and [...] Read more.
Considerable attention has been devoted to the development of nanomaterial-based photoacoustic transmitters for ultrasound therapy and diagnosis applications. Here, we fabricate and characterize candle-soot nanoparticles (CSNPs) and polydimethylsiloxane (PDMS) composite-based photoacoustic transmitters, based on a solution process, not just to achieve high-frequency and high-amplitude pressure outputs, but also to develop physically stretchable ultrasound transmitters. Owing to its non-porous and non-agglomerative characteristics, the composite exhibits unique photo-thermal and mechanical properties. The output pressure amplitudes from CSNPs–PDMS composites were 20–26 dB stronger than those of Cr film, used as a reference. The proposed transmitters also offered a center frequency of 2.44–13.34 MHz and 6-dB bandwidths of 5.80–13.62 MHz. Importantly, we characterize the mechanical robustness of CSNPs–PDMS quantitatively, by measuring laser-damage thresholds, to evaluate the upper limit of laser energy that can be ultimately used as an input, i.e., proportional to the maximum-available pressure output. The transmitters could endure an input laser fluence of 54.3–108.6 mJ·cm−2. This is 1.65–3.30 times higher than the Cr film, and is significantly higher than the values of other CSNPs–PDMS transmitters reported elsewhere (22–81 mJ·cm−2). Moreover, we characterized the strain-dependent photoacoustic output of a stretchable nanocomposite film, obtained by delaminating it from the glass substrate. The transmitter could be elongated elastically up to a longitudinal strain of 0.59. Under this condition, it maintained a center frequency of 6.72–9.44 MHz, and 6-dB bandwidth ranges from 12.05 to 14.02 MHz. We believe that the stretchable CSNPs–PDMS composites would be useful in developing patch-type ultrasound devices conformally adhered on skin for diagnostic and therapeutic applications. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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Article
Highly Integrated Elastic Island-Structured Printed Circuit Board with Controlled Young’s Modulus for Stretchable Electronics
Micromachines 2020, 11(6), 617; https://doi.org/10.3390/mi11060617 - 25 Jun 2020
Viewed by 853
Abstract
A stretchable printed circuit board (PCB), which is an essential component of next-generation electronic devices, should be highly stretchable even at high levels of integration, as well as durable under repetitive stretching and patternable. Herein, an island-structured stretchable PCB composed of materials with [...] Read more.
A stretchable printed circuit board (PCB), which is an essential component of next-generation electronic devices, should be highly stretchable even at high levels of integration, as well as durable under repetitive stretching and patternable. Herein, an island-structured stretchable PCB composed of materials with controlled Young’s modulus and viscosity by adding a reinforcing agent or controlling the degree of crosslinking is reported. Each material was fabricated with the most effective structures through a 3D printer. The PCB was able to stretch 71.3% even when highly integrated and was patterned so that various components could be mounted. When fully integrated, the stress applied to the mounted components was reduced by 99.9% even when stretched by over 70%. Consequently, a 4 × 4 array of capacitance sensors in a stretchable keypad demonstration using our PCB was shown to work, even at 50% stretching of the PCB. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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Article
Investigation on Threshold Voltage Adjustment of Threshold Switching Devices with HfO2/Al2O3 Superlattice on Transparent ITO/Glass Substrate
Micromachines 2020, 11(5), 525; https://doi.org/10.3390/mi11050525 - 21 May 2020
Viewed by 966
Abstract
Threshold voltage adjustment in threshold switching (TS) devices with HfO2/Al2O3 superlattice (by means of changing the cycle ratio of HfO2 to Al2O3 in atomic layer deposition) is investigated to implement a transparent cross-point array. [...] Read more.
Threshold voltage adjustment in threshold switching (TS) devices with HfO2/Al2O3 superlattice (by means of changing the cycle ratio of HfO2 to Al2O3 in atomic layer deposition) is investigated to implement a transparent cross-point array. TS devices with different cycle ratios (i.e., 3:1, 3:2, and 3:3) were fabricated and studied. The threshold voltage of the devices was increased from 0.9 V to 3.2 V, as the relative contents of Al2O3 layer in the superlattice were increased. At the same time, it is demonstrated that the off-resistance values of the devices were enhanced from 2.6 × 109 to 6 × 1010 Ω as the atomic layer deposition (ALD) cycle ratio of HfO2 to Al2O3 layer was adjusted from 3:1 to 3:3. However, the hold voltage and the on-current values were almost identical for the three devices. These results can be understood using the larger barrier height of Al2O3 layer than that of HfO2 layer. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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Article
A Skin-Conformal, Stretchable, and Breathable Fiducial Marker Patch for Surgical Navigation Systems
Micromachines 2020, 11(2), 194; https://doi.org/10.3390/mi11020194 - 13 Feb 2020
Viewed by 1184
Abstract
Augmented reality (AR) surgical navigation systems have attracted considerable attention as they assist medical professionals in visualizing the location of ailments within the human body that are not readily seen with the naked eye. Taking medical imaging with a parallel C-shaped arm (C-arm) [...] Read more.
Augmented reality (AR) surgical navigation systems have attracted considerable attention as they assist medical professionals in visualizing the location of ailments within the human body that are not readily seen with the naked eye. Taking medical imaging with a parallel C-shaped arm (C-arm) as an example, surgical sites are typically targeted using an optical tracking device and a fiducial marker in real-time. These markers then guide operators who are using a multifunctional endoscope apparatus by signaling the direction or distance needed to reach the affected parts of the body. In this way, fiducial markers are used to accurately protect the vessels and nerves exposed during the surgical process. Although these systems have already shown potential for precision implantation, delamination of the fiducial marker, which is a critical component of the system, from human skin remains a challenge due to a mechanical mismatch between the marker and skin, causing registration problems that lead to poor position alignments and surgical degradation. To overcome this challenge, the mechanical modulus and stiffness of the marker patch should be lowered to approximately 150 kPa, which is comparable to that of the epidermis, while improving functionality. Herein, we present a skin-conformal, stretchable yet breathable fiducial marker for the application in AR-based surgical navigation systems. By adopting pore patterns, we were able to create a fiducial marker with a skin-like low modulus and breathability. When attached to the skin, the fiducial marker was easily identified using optical recognition equipment and showed skin-conformal adhesion when stretched and shrunk repeatedly. As such, we believe the marker would be a good fiducial marker candidate for patients under surgical navigation systems. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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Article
Wire Electrodes Embedded in Artificial Conduit for Long-term Monitoring of the Peripheral Nerve Signal
Micromachines 2019, 10(3), 184; https://doi.org/10.3390/mi10030184 - 13 Mar 2019
Cited by 3 | Viewed by 1865
Abstract
Massive efforts to develop neural interfaces have been made for controlling prosthetic limbs according to the will of the patient, with the ultimate goal being long-term implantation. One of the major struggles is that the electrode’s performance degrades over time due to scar [...] Read more.
Massive efforts to develop neural interfaces have been made for controlling prosthetic limbs according to the will of the patient, with the ultimate goal being long-term implantation. One of the major struggles is that the electrode’s performance degrades over time due to scar formation. Herein, we have developed peripheral nerve electrodes with a cone-shaped flexible artificial conduit capable of protecting wire electrodes from scar formation. The wire electrodes, which are composed of biocompatible alloy materials, were embedded in the conduit where the inside was filled with collagen to allow the damaged nerves to regenerate into the conduit and interface with the wire electrodes. After implanting the wire electrodes into the sciatic nerve of a rat, we successfully recorded the peripheral neural signals while providing mechanical stimulation. Remarkably, we observed the external stimuli-induced nerve signals at 19 weeks after implantation. This is possibly due to axon regeneration inside our platform. To verify the tissue response of our electrodes to the sciatic nerve, we performed immunohistochemistry (IHC) and observed axon regeneration without scar tissue forming inside the conduit. Thus, our strategy has proven that our neural interface can play a significant role in the long-term monitoring of the peripheral nerve signal. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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Review

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Review
Recent Developments in Ozone Sensor Technology for Medical Applications
Micromachines 2020, 11(6), 624; https://doi.org/10.3390/mi11060624 - 26 Jun 2020
Cited by 5 | Viewed by 1117
Abstract
There is increasing interest in the utilisation of medical gases, such as ozone, for the treatment of herniated disks, peripheral artery diseases, and chronic wounds, and for dentistry. Currently, the in situ measurement of the dissolved ozone concentration during the medical procedures in [...] Read more.
There is increasing interest in the utilisation of medical gases, such as ozone, for the treatment of herniated disks, peripheral artery diseases, and chronic wounds, and for dentistry. Currently, the in situ measurement of the dissolved ozone concentration during the medical procedures in human bodily liquids and tissues is not possible. Further research is necessary to enable the integration of ozone sensors in medical and bioanalytical devices. In the present review, we report selected recent developments in ozone sensor technology (2016–2020). The sensors are subdivided into ozone gas sensors and dissolved ozone sensors. The focus thereby lies upon amperometric and impedimetric as well as optical measurement methods. The progress made in various areas—such as measurement temperature, measurement range, response time, and recovery time—is presented. As inkjet-printing is a new promising technology for embedding sensors in medical and bioanalytical devices, the present review includes a brief overview of the current approaches of inkjet-printed ozone sensors. Full article
(This article belongs to the Special Issue Deformable Bioelectronics Based on Functional Micro/nanomaterials)
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