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

Deadline for manuscript submissions: closed (15 March 2020) | Viewed by 41609

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Prof. Dr. Dong-Weon Lee

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Guest Editor

MEMS and Nanotechnology Laboratory, School of Mechanical Engineering, Chonnam National University, Gwangju 61186, Korea
Interests: energy harvester; biomedical MEMS; micro- and nano-fabrication; cantilevers

Prof. Dr. Jeong-Bong Lee

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Guest Editor

Electrical and Computer Engineering, Baylor University, Waco, TX 76798-7356, USA
Interests: MEMS; liquid metals; nanophotonic; bio devices; sensors
Special Issues, Collections and Topics in MDPI journals

Prof. Hongsoo Choi

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Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea
Interests: piezoelectric MEMS; microrobot; biomedical MEMS; micromachined ultrasonic transducer

Prof. Dr. Sang-Jae Kim

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Guest Editor

Department of Mechatronics Engineering, Jeju National University, Jeju, Jeju-si 63243, Republic of Korea
Interests: self-charging power cell; hybrid fuel cell; energy harvesting; nanogenerator; nanobiosensor
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue will publish selected papers from the 5th International Conference on Advanced Electromaterials (ICAE 2019, http://www.icae.kr/), 5-8 November 2019, in Jeju, Korea.

The ICAE is a bi-annual conference series hosted by The Korean Institute of Electrical and Electronic Material Engineers focusing on all aspects of "electromaterials". We welcome manuscripts on the following topics:

ferroelectric and piezoelectric materials and devices;
green energy materials and devices;
solar cells and fuel cells;
functional thin films and devices;
energy storage materials and devices;
transparent electronics;
printable electronics;
smart nano-materials and devices;
emerging optoelectronic materials and devices based on LEDs and OLEDs;
biomedical materials and devices.

Papers attracting most interest at the conference, or that provide novel contributions, have been selected for publication in Micromachines. These papers will be peer-reviewed for validation of research results, developments and applications.

Prof. Dr. Dong-Weon Lee
Prof. Jeong-Bong Lee
Prof. Hongsoo Choi
Prof. Sang-Jae Kim
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. 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 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 (11 papers)

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Editorial

Jump to: Research

3 pages, 148 KiB

Open AccessEditorial

Editorial for the Special Issue on the ICAE 2019

by Hongsoo Choi, Dong-Weon Lee, Jeong-Bong Lee and Sang-Jae Kim

Micromachines 2020, 11(9), 874; https://doi.org/10.3390/mi11090874 - 20 Sep 2020

Viewed by 1473

Abstract

This special issue is a collection of 10 selected papers after presenting at the Fifth International Conference on Advanced Electromaterials (ICAE 2019), held in Jeju, South Korea on 5–8 November 2019 [...] Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

Research

Jump to: Editorial

11 pages, 3853 KiB

Open AccessArticle

Development of a High-Density Piezoelectric Micromachined Ultrasonic Transducer Array Based on Patterned Aluminum Nitride Thin Film

by Eunjung Shin, Hong Goo Yeo, Ara Yeon, Changzhu Jin, Wonki Park, Sung-Chul Lee and Hongsoo Choi

Micromachines 2020, 11(6), 623; https://doi.org/10.3390/mi11060623 - 26 Jun 2020

Cited by 26 | Viewed by 4675

Abstract

This study presents the fabrication and characterization of a piezoelectric micromachined ultrasonic transducer (pMUT; radius: 40 µm) using a patterned aluminum nitride (AlN) thin film as the active piezoelectric material. A 20 × 20 array of pMUTs using a 1 µm thick AlN thin film was designed and fabricated on a 2 × 2 mm² footprint for a high fill factor. Based on the electrical impedance and phase of the pMUT array, the electromechanical coefficient was ~1.7% at the average resonant frequency of 2.82 MHz in air. Dynamic displacement of the pMUT surface was characterized by scanning laser Doppler vibrometry. The pressure output while immersed in water was 19.79 kPa when calculated based on the peak displacement at the resonant frequency. The proposed AlN pMUT array has potential applications in biomedical sensing for healthcare, medical imaging, and biometrics. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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14 pages, 3933 KiB

Open AccessArticle

Polymer-Based Functional Cantilevers Integrated with Interdigitated Electrode Arrays—A Novel Platform for Cardiac Sensing

by Pooja P. Kanade, Nomin-Erdene Oyunbaatar and Dong-Weon Lee

Micromachines 2020, 11(4), 450; https://doi.org/10.3390/mi11040450 - 24 Apr 2020

Cited by 12 | Viewed by 3547

Abstract

Heart related ailments are some of the most common causes for death in the world, and some of the causes are cardiac toxicity due to drugs. Several platforms have been developed in this regard over the years that can measure electrical or mechanical behavior of cardiomyocytes. In this study, we have demonstrated a biomedical device that can simultaneously measure electrophysiology and contraction force of cardiomyocytes. This dual-function device is composed of a photosensitive polymer-based cantilever, with a pair of metal-based interdigitated electrodes on its surface, such that the cantilever can measure the contraction force of cardiomyocytes and the electrodes can measure the impedance between cells and substrate. The cantilever is patterned with microgrooves so that the cardiomyocytes can align to the cantilever in order to make a higher cantilever deflection in response to contraction force. Preliminary experimental results have identified the potential for use in the drug-induced cardiac toxicity tests, and further optimization is desirable to extend the technique to various bio-sensor areas. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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10 pages, 2667 KiB

Open AccessArticle

An Implanted Magnetic Microfluidic Pump for In Vivo Bone Remodeling Applications

by Ziyu Chen, Sunggi Noh, Rhonda D. Prisby and Jeong-Bong Lee

Micromachines 2020, 11(3), 300; https://doi.org/10.3390/mi11030300 - 13 Mar 2020

Cited by 18 | Viewed by 4004

Abstract

Modulations of fluid flow inside the bone intramedullary cavity has been found to stimulate bone cellular activities and augment bone growth. However, study on the efficacy of the fluid modulation has been limited to external syringe pumps connected to the bone intramedullary cavity through the skin tubing. We report an implantable magnetic microfluidic pump which is suitable for in vivo studies in rodents. A compact microfluidic pump (22 mm diameter, 5 mm in thickness) with NdFeB magnets was fabricated in polydimethylsiloxane (PDMS) using a set of stainless-steel molds. An external actuator with a larger magnet was used to wirelessly actuate the magnetic microfluidic pump. The characterization of the static pressure of the microfluidic pump as a function of size of magnets was assessed. The dynamic pressure of the pump was also characterized to estimate the output of the pump. The magnetic microfluidic pump was implanted into the back of a Fischer-344 rat and connected to the intramedullary cavity of the femur using a tube. On-demand wireless magnetic operation using an actuator outside of the body was found to induce pressure modulation of up to 38 mmHg inside the femoral intramedullary cavity of the rat. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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13 pages, 3316 KiB

Open AccessArticle

Free-Standing PVDF/Reduced Graphene Oxide Film for All-Solid-State Flexible Supercapacitors towards Self-Powered Systems

by Parthiban Pazhamalai, Vimal Kumar Mariappan, Surjit Sahoo, Woo Young Kim, Young Sun Mok and Sang-Jae Kim

Micromachines 2020, 11(2), 198; https://doi.org/10.3390/mi11020198 - 14 Feb 2020

Cited by 21 | Viewed by 3922

Abstract

The development of polymer-based devices has attracted much attention due to their miniaturization, flexibility, lightweight and sustainable power sources with high efficiency in the field of wearable/portable electronics, and energy system. In this work, we proposed a polyvinylidene fluoride (PVDF)-based composite matrix for both energy harvesting and energy storage applications. The physicochemical characterizations, such as X-ray diffraction, laser Raman, and field-emission scanning electron microscopy (FE-SEM) analyses, were performed for the electrospun PVDF/sodium niobate and PVDF/reduced graphene oxide composite film. The electrospun PVDF/sodium niobate nanofibrous mat has been utilized for the energy harvester which shows an open circuit voltage of 40 V (peak to peak) at an applied compressive force of 40 N. The PVDF/reduced graphene oxide composite film acts as the electrode for the symmetric supercapacitor (SSC) device fabrication and investigated for their supercapacitive properties. Finally, the self-charging system has been assembled using PVDF/sodium niobate (energy harvester), and PVDF/reduced graphene oxide SSC (energy storage) and the self-charging capability is investigated. The proposed self-charging system can create a pathway for the all-polymer based composite high-performance self-charging system. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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11 pages, 5847 KiB

Open AccessArticle

Effect of Contact Plug Deposition Conditions on Junction Leakage and Contact Resistance in Multilevel CMOS Logic Interconnection Device

by Yinhua Cui, Jeong Yeul Jeong, Yuan Gao and Sung Gyu Pyo

Micromachines 2020, 11(2), 170; https://doi.org/10.3390/mi11020170 - 06 Feb 2020

Cited by 2 | Viewed by 3147

Abstract

Here, we developed the optimal conditions in terms of physical and electrical characteristics of the barrier and tungsten (W) deposition process of a contact module, which is the segment connecting the device and the multi-layer metallization (MLM) metal line in the development of 100 nm-class logic devices. To confirm its applicability to the logic contact of barrier and W films, a contact hole was formed, first to check the bottom coverage and the filling status of each film, then to check the electrical resistance and leakage characteristics to analyze the optimal conditions. At an aspect ratio of 3.89:1, ionized metal plasma (IMP) Ti had a bottom coverage of 40.9% and chemical vapor deposition (CVD) titanium nitride (TiN) of 76.2%, confirming that it was possible to apply the process to 100 nm logic contacts. W filling was confirmed, and a salicide etching rate (using Radio Frequency (RF) etch) of 13–18 Å/s at a 3.53:1 aspect ratio was applied. The etching rate on the thermal oxide plate was 9 Å/s. As the RF etch amount increased from 50–100 Å, the P active resistance increased by 0.5–1 Ω. The resistance also increased as the amount of IMP Ti deposition increased to 300 Å. A measurement of the borderless contact junction leakage current indicated that the current in the P + N well increased by more than an order of magnitude when IMP Ti 250 Å or more was deposited. The contact resistance value was 0.5 Ω. An AC bias improved the IMP Ti deposition rate by 10% in bottom coverage, but there was no significant difference in contact resistance. In the case of applying IMP TiN, the overall contact resistance decreased to 2 Ω compared to CVD TiN, but the distribution characteristics were poor. The best results were obtained under the conditions of RF etch 50 Å, IMP Ti 200 Å, and CVD TiN 2 × 50 Å. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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12 pages, 4914 KiB

Open AccessArticle

3D Microlithography Using an Integrated System of 5-mm UV-LEDs with a Tilt-Rotational Sample Holder

by Sabera Fahmida Shiba, Hyeongmin Jeon, Jong-Soo Kim, Jong-Eun Kim and Jungkwun Kim

Micromachines 2020, 11(2), 157; https://doi.org/10.3390/mi11020157 - 31 Jan 2020

Cited by 6 | Viewed by 3318

Abstract

This paper demonstrates a 3D microlithography system where an array of 5 mm Ultra Violet-Light Emitting Diode (UV-LED) acts as a light source. The unit of the light source is a UV-LED, which comes with a length of about 8.9 mm and a diameter of 5 mm. The whole light source comprises 20 × 20 matrix of such 5 mm UV-LEDs giving a total number of 400 LEDs which makes it a very favorable source with a large area for having a batch production of the desired microstructures. This light source is able to give a level of precision in microfabrication which cannot be obtained using commercial 3D printers. The whole light source performs continuous rotational movement once it is turned on. This can also move up and down in a vertical direction. This multidirectional light source also comprises a multidirectional sample holder. The light source teaming up with the multidirectional sample holder highly facilitates the process of fabrication of a huge range of 3D structures. This article also describes the different levels of characterization of the system and demonstrates several fabricated 3D microstructures including high aspect ratio vertical micro towers, twisted turbine structures, triangles, inclined pillar ‘V’ structures, and hollow horn structures as well. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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10 pages, 3333 KiB

Open AccessArticle

Performance Improvement of Ring-Type PZT Ceramics for Ultrasonic Dispersion System

by Young Min Choi, Yang Lae Lee, Eui Su Lim, Mojiz Abbas Trimzi, Seon Ae Hwangbo and Young Bog Ham

Micromachines 2020, 11(2), 144; https://doi.org/10.3390/mi11020144 - 28 Jan 2020

Cited by 9 | Viewed by 3358

Abstract

This study has been based on the examination of the characterization of ring-type lead zirconate titanate (PZT) ceramics for high-intensity focused ultrasonic dispersion system. The ring-type PZT ceramics were fabricated by the powder molding method. The mechanical properties, dielectric constant, and microstructure of the ceramics were investigated. Consequently, the density of the ceramics was increased with increasing forming pressure while the density of ceramics that were sintered at 1350 °C was decreased due to over-sintering. Furthermore, the mechanical properties were excellent at the higher forming pressure. The dielectric property of the ring-type PZT ceramics was not clearly influenced by the manufacturing and sintering conditions. The abnormal grain growth of the ceramics, however, could be prevented by a lower heating rate in addition to reducing the porosity. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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18 pages, 6204 KiB

Open AccessArticle

Development of a Piezo-Driven Liquid Jet Dispenser with Hinge-Lever Amplification Mechanism

by Mojiz Abbas Trimzi, Young Bog Ham, Byeung Cheol An, Young Min Choi, Jung Ho Park and So Nam Yun

Micromachines 2020, 11(2), 117; https://doi.org/10.3390/mi11020117 - 21 Jan 2020

Cited by 12 | Viewed by 6263

Abstract

Owing to the quick response, compact structure, high precision, huge blocking force generation, and ease of operation, piezoelectric actuators are urgently being adopted in the field of advanced dispensing for jetting performance improvement and fulfillment of precision requirements in microelectronics packaging, adhesive bonding, and miniaturization industry. This research focuses on the fundamental design and development of a piezo-electrically driven compact fluid dispenser using the principle of a class-one lever for amplification of needle displacement, and enhancement of application areas of the developed jet dispenser. Using fundamental lever principle, geometry-based modelling is carried out to fabricate a working prototype of a normally closed hinge-lever type dispenser. Preliminary experiments are carried out to witness the workability of the fabricated dispenser to deliver 100 dots of working fluid per second that will provide a novel device for dispensing of various fluids, and the proposed amplification mechanism suits various other piezoelectric applications as well. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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11 pages, 1359 KiB

Open AccessArticle

Role of a 193 nm ArF Excimer Laser in Laser-Assisted Plasma-Enhanced Chemical Vapor Deposition of SiN_x for Low Temperature Thin Film Encapsulation

by Kunsik An, Ho-Nyun Lee, Kwan Hyun Cho, Seung-Woo Lee, David J. Hwang and Kyung-Tae Kang

Micromachines 2020, 11(1), 88; https://doi.org/10.3390/mi11010088 - 13 Jan 2020

Cited by 7 | Viewed by 3727

Abstract

In this study, silicon nitride thin films are deposited on organic polyethylene-naphthalate (PEN) substrates by laser assisted plasma enhanced chemical vapor deposition (LAPECVD) at a low temperature (150 °C) for the purpose of evaluating the encapsulation performance. A plasma generator is placed above the sample stage as conventional plasma enhanced chemical vapor deposition (PECVD) configuration, and the excimer laser beam of 193 nm wavelength illuminated in parallel to the sample surface is coupled to the reaction zone between the sample and plasma source. Major roles of the laser illumination in LAPECVD process are to compete with or complement the plasma decomposition of reactant gases. While a laser mainly decomposes ammonia molecules in the plasma, it also contributes to the photolysis of silane in the plasma state, possibly through the resulting hydrogen radicals and the excitation of intermediate disilane products. It will also be shown that the LAPECVD with coupled laser illumination of 193 nm wavelength improves the deposition rate of silicon nitride thin film, and the encapsulation performance evaluated via the measurement of water vapor transmission rate (WVTR). Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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12 pages, 2711 KiB

Open AccessArticle

Process Optimization of Via Plug Multilevel Interconnections in CMOS Logic Devices

by Yinhua Cui, Jeong Yeul Jeong, Yuan Gao and Sung Gyu Pyo

Micromachines 2020, 11(1), 32; https://doi.org/10.3390/mi11010032 - 25 Dec 2019

Cited by 4 | Viewed by 3017

Abstract

This paper reports on the optimization of the device and wiring in a via structure applied to multilevel metallization (MLM) used in CMOS logic devices. A MLM via can be applied to the Tungsten (W) plug process of the logic device by following the most optimized barrier deposition scheme of RF etching 200 Å IMP Ti (ion metal plasma titanium) 200 Å CVD TiN (titanium nitride deposited by chemical vapor deposition) 2 × 50 Å. The resistivities of the glue layer and barrier, i.e., IMP Ti and CVD TiN, were 73 and 280 μΩ·cm, respectively, and the bottom coverages were 57% and 80%, respectively, at a 3.2:1 aspect ratio (A/R). The specific resistance of the tungsten film was approximately 11.5 μΩ·cm, and it was confirmed that the via filling could be performed smoothly. RF etching and IMP Ti should be at least 200 Å each, and CVD TiN can be performed satisfactorily with the existing 2 × 50 Å process. Tungsten deposition showed no difference in the via resistance with deposition temperature and SiH₄ reduction time. When the barrier scheme of RF etching 200 Å IMP Ti 200 ÅCVD TiN 2 × 50 Å was applied, the via resistance was less than 20 Ω, even with a side misalignment of 0.05 μm and line-end misalignment of ~0.1 μm. Full article

(This article belongs to the Special Issue Selected Papers from the ICAE 2019)

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