Micromachines

13 pages, 1391 KiB

Open AccessArticle

Push/Pull Inequality Based High-Speed On-Chip Mixer Enhanced by Wettability

by Toshio Takayama, Naoya Hosokawa, Chia-Hung Dylan Tsai and Makoto Kaneko

Micromachines 2020, 11(10), 950; https://doi.org/10.3390/mi11100950 - 21 Oct 2020

Cited by 1 | Viewed by 2089

In this paper, a high-speed on-chip mixer using two effects is proposed, i.e., push/pull inequality and wettability. Push/pull inequality and wettability are effective for generating a rotational fluid motion in the chamber and for enhancing the rotational speed by reducing the viscous loss [...] Read more.

In this paper, a high-speed on-chip mixer using two effects is proposed, i.e., push/pull inequality and wettability. Push/pull inequality and wettability are effective for generating a rotational fluid motion in the chamber and for enhancing the rotational speed by reducing the viscous loss between the liquid and channel wall, respectively. An on-chip mixer is composed of three components, a microfluidic channel for making the main fluid flow, a circular chamber connected to the channel for generating a rotational flow, and an actuator connected at the end of the channel allowing a push/pull motion to be applied to the liquid in the main channel. The flow patterns in the chamber under push/pull motions are nonreversible for each motion and, as a result, produce one-directional torque to the fluid in the circular chamber. This nonreversible motion is called push/pull inequality and eventually creates a swirling flow in the chamber. Using hydrophilic treatments, we executed the experiment with a straight channel and a circular chamber to clarify the mixing characteristics at different flow speeds. According to the results, it is confirmed that the swirling velocity under appropriately tuned wettability is 100 times faster than that without tuning. Full article

(This article belongs to the Special Issue Micro Process-Devices)

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11 pages, 15992 KiB

Open AccessArticle

Improved Rectification and Osmotic Power in Polyelectrolyte-Filled Mesopores

by Ding-Cheng Zheng and Li-Hsien Yeh

Micromachines 2020, 11(10), 949; https://doi.org/10.3390/mi11100949 - 21 Oct 2020

Cited by 10 | Viewed by 2510

Abstract

Ample studies have shown the use of nanofluidics in the ionic diode and osmotic power generation, but similar ionic devices performed with large-sized mesopores are still poorly understood. In this study, we model and realize the mesoscale ionic diode and osmotic power generator, [...] Read more.

Ample studies have shown the use of nanofluidics in the ionic diode and osmotic power generation, but similar ionic devices performed with large-sized mesopores are still poorly understood. In this study, we model and realize the mesoscale ionic diode and osmotic power generator, composed of an asymmetric cone-shaped mesopore with its narrow opening filled with a polyelectrolyte (PE) layer with high space charges. We show that, only when the space charge density of a PE layer is sufficiently large (>

1 \times 10^{6} {C / m}^{3}

), the considered mesopore system is able to create an asymmetric ionic distributions in the pore and then rectify ionic current. As a result, the output osmotic power performance can be improved when the filled PE carries sufficiently high space charges. For example, the considered PE-filled mesopore system can show an amplification of the osmotic power of up to 35.1-fold, compared to the bare solid-state mesopore. The findings provide necessary information for the development of large-sized ionic diode and osmotic power harvesting device. Full article

(This article belongs to the Special Issue Energy Generation from Micro/Nanofluidics)

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19 pages, 11071 KiB

Open AccessArticle

Fast Fabrication of Complex Surficial Micro-Features Using Sequential Lithography and Jet Electrochemical Machining

by Ming Wu, Krishna Kumar Saxena, Zhongning Guo, Jun Qian and Dominiek Reynaerts

Micromachines 2020, 11(10), 948; https://doi.org/10.3390/mi11100948 - 20 Oct 2020

Cited by 11 | Viewed by 2414

Abstract

This paper presents fabrication of complex surficial micro-features employing a cross-innovative hybrid process inspired from lithography and Jet-ECM. The process is referred here as mask electrolyte jet machining (MEJM). MEJM is a non-contact machining process which combines high resolution of lithography and greater [...] Read more.

This paper presents fabrication of complex surficial micro-features employing a cross-innovative hybrid process inspired from lithography and Jet-ECM. The process is referred here as mask electrolyte jet machining (MEJM). MEJM is a non-contact machining process which combines high resolution of lithography and greater flexibility of Jet-ECM. It is a non-contact process which can fabricate variety of microstructures on difficult-to-machine materials without need of expensive tooling. The presented work demonstrates the process performance of this technology by statistical analysis and multivariate kernel density estimation (KDE) based on probabilistic density function. Micro-letters are fabricated as an example of complex surficial structure comprising of multiple intersecting, straight and curved grooves. The processing response is characterized in terms of geometrical size, similarity ratio, and cumulative shape deviation. Experimental results demonstrated that micro letters with good repeatability (minimum SD of shape error ratio 0.297%) and shape accuracy (minimum shape error of 0.039%) can be fabricated with this technology. The results suggest MEJM could be a promising technology for batch manufacturing of surface microstructures with high productivity. Full article

(This article belongs to the Section E：Engineering and Technology)

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17 pages, 16524 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Future Application of Organ-on-a-Chip Technologies as Proving Grounds for MicroBioRobots

by Haley C. Fuller, Ting-Yen Wei, Michael R. Behrens and Warren C. Ruder

Micromachines 2020, 11(10), 947; https://doi.org/10.3390/mi11100947 - 20 Oct 2020

Cited by 8 | Viewed by 4507

Abstract

An evolving understanding of disease pathogenesis has compelled the development of new drug delivery approaches. Recently, bioinspired microrobots have gained traction as drug delivery systems. By leveraging the microscale phenomena found in physiological systems, these microrobots can be designed with greater maneuverability, which [...] Read more.

An evolving understanding of disease pathogenesis has compelled the development of new drug delivery approaches. Recently, bioinspired microrobots have gained traction as drug delivery systems. By leveraging the microscale phenomena found in physiological systems, these microrobots can be designed with greater maneuverability, which enables more precise, controlled drug release. Their function could be further improved by testing their efficacy in physiologically relevant model systems as part of their development. In parallel with the emergence of microscale robots, organ-on-a-chip technologies have become important in drug discovery and physiological modeling. These systems reproduce organ-level functions in microfluidic devices, and can also incorporate specific biological, chemical, and physical aspects of a disease. This review highlights recent developments in both microrobotics and organ-on-a-chip technologies and envisions their combined use for developing future drug delivery systems. Full article

(This article belongs to the Special Issue Microengineered Physiological Systems for Disease Modeling and Drug Testing)

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27 pages, 4788 KiB

Open AccessReview

Application of Stereolithography Based 3D Printing Technology in Investment Casting

by Muslim Mukhtarkhanov, Asma Perveen and Didier Talamona

Micromachines 2020, 11(10), 946; https://doi.org/10.3390/mi11100946 - 19 Oct 2020

Cited by 74 | Viewed by 8794

Abstract

Advanced methods for manufacturing high quality parts should be used to ensure the production of competitive products for the world market. Investment casting (IC) is a process where a wax pattern is used as a sacrificial pattern to manufacture high precision casting of [...] Read more.

Advanced methods for manufacturing high quality parts should be used to ensure the production of competitive products for the world market. Investment casting (IC) is a process where a wax pattern is used as a sacrificial pattern to manufacture high precision casting of solid metal parts. Rapid casting is in turn, a technique that eases the IC process by combining additive manufacturing (AM) technologies with IC. The use of AM technologies to create patterns for new industrial products is a unique opportunity to develop cost-effective methods for producing investment casting parts in a timely manner. Particularly, stereolithography (SLA) based AM is of interest due to its high dimensional accuracy and the smooth surface quality of the printed parts. From the first appearance of commercially available SLA printers in the market, it took a few decades until desktop SLA printers became available to consumers at a reasonable price. Therefore, the aim of this review paper is to analyze the state-of-the-art and applicability of SLA based 3D printing technology in IC manufacturing, as SLA based AM technologies have been gaining enormous popularity in recent times. Other AM techniques in IC are also reviewed for comparison. Moreover, the SLA process parameters, material properties, and current issues are discussed. Full article

(This article belongs to the Special Issue Micro-Manufacturing and Applications)

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15 pages, 20310 KiB

Open AccessArticle

Damping Asymmetry Trimming Based on the Resistance Heat Dissipation for Coriolis Vibratory Gyroscope in Whole-Angle Mode

by Kechen Guo, Yulie Wu, Yongmeng Zhang, Jiangkun Sun, Dingbang Xiao and Xuezhong Wu

Micromachines 2020, 11(10), 945; https://doi.org/10.3390/mi11100945 - 19 Oct 2020

Cited by 8 | Viewed by 2186

Abstract

Damping asymmetry is one of the most important factors that determines the performance of Coriolis Vibratory Gyroscope. In this paper, a novel damping tuning method for the resonator with parallel plate capacitors is presented. This damping tuning method is based on resistance heat [...] Read more.

Damping asymmetry is one of the most important factors that determines the performance of Coriolis Vibratory Gyroscope. In this paper, a novel damping tuning method for the resonator with parallel plate capacitors is presented. This damping tuning method is based on resistance heat dissipation and the tuning effect is characterized by the control force in Whole-Angle mode. As the damping tuning and stiffness tuning in the resonator with parallel plate capacitors are coupled with each other, a corresponding tuning system is designed. To verify the tuning effects, experiments are conducted on a hemispherical resonator gyroscope with Whole-Angle mode. The damping tuning theories is demonstrated by the testing results and 87% of the damping asymmetry is reduced by this tuning method with a cost of 3% decaying time. Furthermore, the angle-dependent drift in rate measurement after tuning is only 15.6% of the one without tuning and the scale factor nonlinearity decreases from 5.49 ppm to 2.66 ppm. The method can be further applied on the damping tuning in other resonators with symmetrical structure. Full article

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18 pages, 10866 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

by Douglas B. Shire, Marcus D. Gingerich, Patricia I. Wong, Michael Skvarla, Stuart F. Cogan, Jinghua Chen, Wei Wang and Joseph F. Rizzo

Micromachines 2020, 11(10), 944; https://doi.org/10.3390/mi11100944 - 19 Oct 2020

Cited by 5 | Viewed by 3602

Abstract

We present a retrospective of unique micro-fabrication problems and solutions that were encountered through over 10 years of retinal prosthesis product development, first for the Boston Retinal Implant Project initiated at the Massachusetts Institute of Technology and at Harvard Medical School’s teaching hospital, [...] Read more.

We present a retrospective of unique micro-fabrication problems and solutions that were encountered through over 10 years of retinal prosthesis product development, first for the Boston Retinal Implant Project initiated at the Massachusetts Institute of Technology and at Harvard Medical School’s teaching hospital, the Massachusetts Eye and Ear—and later at the startup company Bionic Eye Technologies, by some of the same personnel. These efforts culminated in the fabrication and assembly of 256+ channel visual prosthesis devices having flexible multi-electrode arrays that were successfully implanted sub-retinally in mini-pig animal models as part of our pre-clinical testing program. We report on the processing of the flexible multi-layered, planar and penetrating high-density electrode arrays, surgical tools for sub-retinal implantation, and other parts such as coil supports that facilitated the implantation of the peri-ocular device components. We begin with an overview of the implantable portion of our visual prosthesis system design, and describe in detail the micro-fabrication methods for creating the parts of our system that were assembled outside of our hermetically-sealed electronics package. We also note the unique surgical challenges that sub-retinal implantation of our micro-fabricated components presented, and how some of those issues were addressed through design, materials selection, and fabrication approaches. Full article

(This article belongs to the Special Issue Micro/Nanofabrication for Retinal Implants)

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10 pages, 3373 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Flexible, Microfluidic, Dispensing System for Screening Drug Combinations

by Mark Davies, Mannthalah Abubaker and Lorraine Bible

Micromachines 2020, 11(10), 943; https://doi.org/10.3390/mi11100943 - 18 Oct 2020

Cited by 4 | Viewed by 2693

Abstract

It is known that in many cases a combination of drugs is more effective than single-drug treatments both for reducing toxicity and increasing efficacy. With the advent of organoid screens, personalised medicine has become possible for many diseases. Automated pipetting to well plates [...] Read more.

It is known that in many cases a combination of drugs is more effective than single-drug treatments both for reducing toxicity and increasing efficacy. With the advent of organoid screens, personalised medicine has become possible for many diseases. Automated pipetting to well plates is the pharmaceutical industry standard for drug screening, but this is relatively expensive and slow. Here, a rotary microfluidic system is presented that can test all possible drug combinations at speed with the use of droplets. For large numbers of combinations, it is shown how the experimental scale is reduced by considering drug dilutions and machine learning. As an example, two cases are considered; the first is a three-ring and three radii configuration and the second is a four ring and forty-eight radii configuration. Between these two, all other cases are shown to be possible. The proposed commercial instrument is shown to be flexible, the user choosing which wells to fill and which driver-computational sub-routine to select. The major issues addressed here are the programming theory of the instrument and the reduction of droplets to be generated by drug dilutions and machine learning. Full article

(This article belongs to the Special Issue Droplet Microfluidics)

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30 pages, 5835 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Electro-Hydrodynamics of Emulsion Droplets: Physical Insights to Applications

by Muhammad Salman Abbasi, Ryungeun Song, Seongsu Cho and Jinkee Lee

Micromachines 2020, 11(10), 942; https://doi.org/10.3390/mi11100942 - 18 Oct 2020

Cited by 20 | Viewed by 5209

Abstract

The field of droplet electrohydrodynamics (EHD) emerged with a seminal work of G.I. Taylor in 1966, who presented the so-called leaky dielectric model (LDM) to predict the droplet shapes undergoing distortions under an electric field. Since then, the droplet EHD has evolved in [...] Read more.

The field of droplet electrohydrodynamics (EHD) emerged with a seminal work of G.I. Taylor in 1966, who presented the so-called leaky dielectric model (LDM) to predict the droplet shapes undergoing distortions under an electric field. Since then, the droplet EHD has evolved in many ways over the next 55 years with numerous intriguing phenomena reported, such as tip and equatorial streaming, Quincke rotation, double droplet breakup modes, particle assemblies at the emulsion interface, and many more. These phenomena have a potential of vast applications in different areas of science and technology. This paper presents a review of prominent droplet EHD studies pertaining to the essential physical insight of various EHD phenomena. Here, we discuss the dynamics of a single-phase emulsion droplet under weak and strong electric fields. Moreover, the effect of the presence of particles and surfactants at the emulsion interface is covered in detail. Furthermore, the EHD of multi-phase double emulsion droplet is included. We focus on features such as deformation, instabilities, and breakups under varying electrical and physical properties. At the end of the review, we also discuss the potential applications of droplet EHD and various challenges with their future perspectives. Full article

(This article belongs to the Special Issue Electrokinetics in Micro-/nanofluidic Devices)

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29 pages, 25287 KiB

Open AccessArticle

Shrinkage-Considered Mold Design for Improvement of Micro/Nano-Structured Optical Element Performance

by Minsu Kim, Eun Song Oh and Moon Kyu Kwak

Micromachines 2020, 11(10), 941; https://doi.org/10.3390/mi11100941 - 17 Oct 2020

Cited by 5 | Viewed by 2693

Abstract

Polymer shrinkage in nano-imprint lithography (NIL) is one of the critical issues that must be considered in order to produce a quality product. Especially, this condition should be considered during the manufacture of optical elements, because micro/nano-structured optical elements should be controlled to [...] Read more.

Polymer shrinkage in nano-imprint lithography (NIL) is one of the critical issues that must be considered in order to produce a quality product. Especially, this condition should be considered during the manufacture of optical elements, because micro/nano-structured optical elements should be controlled to fit the desired shape in order to achieve the intended optical performance. In this paper, during NIL, we characterized the shrinkage of polymeric resin on micro lens array (MLA), which is one of the representative micro/nano-structured optical elements. The curvature shape and optical performance of MLA were measured to check the shrinkage tendency during the process. The master mold of MLA was generated by the two-photon polymerization (2PP) additive manufacturing method, and the tested samples were replicated from the master mold with NIL. Several types of resin were adjusted to prepare the specimens, and the shrinkage effects in each case were compared. The shrinkage showed different trends based on the NIL materials and MLA shapes. These characterizations can be applied to compensate for the MLA design, and the desired performance of MLA products can be achieved with a corrected master mold. Full article

(This article belongs to the Section E：Engineering and Technology)

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19 pages, 10197 KiB

Open AccessArticle

Roll Angular Rate Measurement for High Spinning Projectiles Based on Redundant Gyroscope System

by Jing Mi, Jie Li, Xi Zhang, Kaiqiang Feng, Chenjun Hu, Xiaokai Wei and Xiaoqiao Yuan

Micromachines 2020, 11(10), 940; https://doi.org/10.3390/mi11100940 - 16 Oct 2020

Cited by 5 | Viewed by 2151

Abstract

Precision-guided projectiles, which can significantly improve the accuracy and efficiency of fire strikes, are on the rise in current military engagements. The accurate measurement of roll angular rate is critical to guide a gun-launched projectile. However, Micro-Electro-Mechanical System (MEMS) gyroscope with low cost [...] Read more.

Precision-guided projectiles, which can significantly improve the accuracy and efficiency of fire strikes, are on the rise in current military engagements. The accurate measurement of roll angular rate is critical to guide a gun-launched projectile. However, Micro-Electro-Mechanical System (MEMS) gyroscope with low cost and large range cannot meet the requirement of high precision roll angular rate measurement due to the limitation by the current technology level. Aiming at the problem, the optimization-based angular rate estimation (OBARS) method specific for projectiles is proposed in this study. First, the output angular rate model of redundant gyroscope system based on the autoregressive integrated moving average (ARIMA) model is established, and then the conventional random error model is improved with the ARIMA model. After that, a Sage-Husa Adaptive Kalman Filter (SHAKF) algorithm that can suppress the time-varying process and measurement noise under the flight condition of the high dynamic of the projectile is designed for the fusion of dynamic data. Finally, simulations and experiments have been carried out to validate the performance of the method. The results demonstrate the proposed method can effectively improve the angular rate accuracy more than the related traditional methods for high spinning projectiles. Full article

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14 pages, 4731 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Micromachined Silicon Platform for Precise Assembly of 2D Multilayer Laue Lenses for High-Resolution X-ray Microscopy

by Wei Xu, Weihe Xu, Nathalie Bouet, Juan Zhou, Hanfei Yan, Xiaojing Huang, Ming Lu, Maxim Zalalutdinov, Yong S. Chu and Evgeny Nazaretski

Micromachines 2020, 11(10), 939; https://doi.org/10.3390/mi11100939 - 15 Oct 2020

Cited by 3 | Viewed by 2681

Abstract

We report on a developed micromachined silicon platform for the precise assembly of 2D multilayer Laue lenses (MLLs) for high-resolution X-ray microscopy. The platform is 10 × 10 mm² and is fabricated on ~500 µm thick silicon wafers through multiple steps of [...] Read more.

We report on a developed micromachined silicon platform for the precise assembly of 2D multilayer Laue lenses (MLLs) for high-resolution X-ray microscopy. The platform is 10 × 10 mm² and is fabricated on ~500 µm thick silicon wafers through multiple steps of photolithography and deep reactive-ion etching. The platform accommodates two linear MLLs in a pre-defined configuration with precise angular and lateral position control. In this work, we discuss the design and microfabrication of the platform, and characterization regarding MLLs assembly, position control, repeatability, and stability. The results demonstrate that a micromachined platform can be used for the assembly of a variety of MLLs with different dimensions and optical parameters. The angular misalignment of 2D MLLs is well controlled in the range of the designed accuracy, down to a few millidegrees. The separation distance between MLLs is adjustable from hundreds to more than one thousand micrometers. The use of the developed platform greatly simplifies the alignment procedure of the MLL optics and reduces the complexity of the X-ray microscope. It is a significant step forward for the development of monolithic 2D MLL nanofocusing optics for high-resolution X-ray microscopy. Full article

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14 pages, 8952 KiB

Open AccessArticle

Uniform Polishing Method of Spherical Lens Based on Material Removal Model of High-Speed Polishing Procedure

by Hao Zhang, Peng Wang, Zexiao Li, Yi Shen and Xiaodong Zhang

Micromachines 2020, 11(10), 938; https://doi.org/10.3390/mi11100938 - 15 Oct 2020

Cited by 5 | Viewed by 4599

Abstract

Although the high-speed polishing technology has been widely applied to obtain an ultra-smooth surface in the field of spherical optical manufacture, it is still mainly used in small-size or easily polished lenses. In the infrared optical system, large-size silicon lenses are often used [...] Read more.

Although the high-speed polishing technology has been widely applied to obtain an ultra-smooth surface in the field of spherical optical manufacture, it is still mainly used in small-size or easily polished lenses. In the infrared optical system, large-size silicon lenses are often used to increase the luminous flux. As is known, the material is hard-polished, it is time-consuming to reduce the surface roughness by iterative polishing and it is difficult to avoid the form accuracy getting worse. To produce an ultra-smooth surface efficiently without destroying the figure, a scientific understanding of material removal in the high-speed polishing process is necessary, which would lead to the process being more deterministic. In this paper, a mathematical model of material removal is developed based on the classic Preston equation. The predicted results of the proposed model show good agreement with the experimental data. Further, a method to achieve uniform polishing can be addressed with a systematic analysis of the key factors affecting material removal and their contribution to spatial non-uniform removal. Finally, the experimental results indicate that the surface roughness of hard-polished spherical optics can be improved efficiently using the uniform polishing method without the surface figure being destroyed. Full article

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13 pages, 10487 KiB

Open AccessArticle

Power Management IC for a Dual-Input-Triple-Output Energy Harvester

by Kai-Meng Mui, Mei-Kum Khaw and Faisal Mohd-Yasin

Micromachines 2020, 11(10), 937; https://doi.org/10.3390/mi11100937 - 15 Oct 2020

Cited by 1 | Viewed by 2871

Abstract

We present the design of a power management integrated circuit that processes harvested energy from radio frequency waves and piezoelectric vibrations. The rectification of piezoelectric and RF sources has a power conversion efficiency (PCE) of 87.73% and 74.70%, respectively. The asynchronous and microcontroller-less [...] Read more.

We present the design of a power management integrated circuit that processes harvested energy from radio frequency waves and piezoelectric vibrations. The rectification of piezoelectric and RF sources has a power conversion efficiency (PCE) of 87.73% and 74.70%, respectively. The asynchronous and microcontroller-less integrated circuit (IC) is designed to be low power, so the bulk of the harvested energy goes to three loads. The output peak powers of 111 μW, 156 μW, and 128 μW will be sufficient to run small devices for RF communication systems. Full article

(This article belongs to the Special Issue Next Generation RFID Transponders)

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10 pages, 3298 KiB

Open AccessArticle

Template Stripping Method-Based Au Nanoarray for Surface-Enhanced Raman Scattering Detection of Antiepileptic Drug

by Tatsuro Endo, Hirotaka Yamada and Kenji Yamada

Micromachines 2020, 11(10), 936; https://doi.org/10.3390/mi11100936 - 14 Oct 2020

Cited by 7 | Viewed by 2497

Abstract

Surface-enhanced Raman scattering (SERS) is a potential candidate for highly sensitive detection of target molecules. A SERS active substrate with a noble metal nanostructure is required for this. However, a SERS active substrate requires complicated fabrication procedures. This in turn makes it difficult [...] Read more.

Surface-enhanced Raman scattering (SERS) is a potential candidate for highly sensitive detection of target molecules. A SERS active substrate with a noble metal nanostructure is required for this. However, a SERS active substrate requires complicated fabrication procedures. This in turn makes it difficult to fabricate highly sensitive SERS active substrates with high reproducibility. To overcome this difficulty, a plasmonic crystal (PC) with periodic noble metal nanostructures was fabricated via the template-stripping method using a polymer-based template. Using SERS active substrates, SERS was successfully achieved using the PC by detecting low concentrations of phenobarbital which is an antiepileptic drug using a commercially available portable Raman module. The PC can be fabricated by demolding the deposited gold layer from a polymer-based template. This method is rapid, economic, and has high reproducibility. SERS can be achieved easily using this PC for a wide variety of applications such as medical, pharmaceutical, and environmental protection. Full article

(This article belongs to the Special Issue Micro and Nano Devices for Cell Analysis)

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17 pages, 6859 KiB

Open AccessArticle

Investigation of a Liquid-Phase Electrode for Micro-Electro-Discharge Machining

by Ruining Huang, Ying Yi, Erlei Zhu and Xiaogang Xiong

Micromachines 2020, 11(10), 935; https://doi.org/10.3390/mi11100935 - 14 Oct 2020

Cited by 3 | Viewed by 2192

Abstract

Micro-electro-discharge machining (μEDM) plays a significant role in miniaturization. Complex electrode manufacturing and a high wear ratio are bottlenecks for μEDM and seriously restrict the manufacturing of microcomponents. To solve the electrode problems in traditional EDM, a µEDM method using liquid metal as [...] Read more.

Micro-electro-discharge machining (μEDM) plays a significant role in miniaturization. Complex electrode manufacturing and a high wear ratio are bottlenecks for μEDM and seriously restrict the manufacturing of microcomponents. To solve the electrode problems in traditional EDM, a µEDM method using liquid metal as the machining electrode was developed. Briefly, a liquid-metal tip was suspended at the end of a capillary nozzle and used as the discharge electrode for sparking the workpiece and removing workpiece material. During discharge, the liquid electrode was continuously supplied to the nozzle to eliminate the effects of liquid consumption on the erosion process. The forming process of a liquid-metal electrode tip and the influence of an applied external pressure and electric field on the electrode shape were theoretically analyzed. The effects of external pressure and electric field on the material removal rate (MRR), liquid-metal consumption rate (LMCR), and groove width were experimentally analyzed. Simulation results showed that the external pressure and electric field had a large influence on the electrode shape. Experimental results showed that the geometry and shape of the liquid-metal electrode could be controlled and constrained; furthermore, liquid consumption could be well compensated, which was very suitable for µEDM. Full article

(This article belongs to the Special Issue Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications)

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12 pages, 3173 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microfluidic Viscometer Using a Suspending Micromembrane for Measurement of Biosamples

by Lelin Liu, Dinglong Hu and Raymond H. W. Lam

Micromachines 2020, 11(10), 934; https://doi.org/10.3390/mi11100934 - 14 Oct 2020

Cited by 17 | Viewed by 3161

Abstract

The viscosity of biofluids such as blood and saliva can reflect an individual’s health conditions, and viscosity measurements are therefore considered in health monitoring and disease diagnosis. However, conventional viscometers can only handle a larger liquid volume beyond the quantity that can be [...] Read more.

The viscosity of biofluids such as blood and saliva can reflect an individual’s health conditions, and viscosity measurements are therefore considered in health monitoring and disease diagnosis. However, conventional viscometers can only handle a larger liquid volume beyond the quantity that can be extracted from a person. Though very effective, micro-sensors based on electrokinetic, ultrasonic, or other principles often have strict requirements for the supporting equipment and complicated procedures and signal processing. Sample contamination is always an important issue. In this paper, we report a microfluidic viscometer requiring a small volume of biosamples (<50 µL) and straightforward operation procedures. It is fabricated with low-cost and biocompatible polymeric materials as one-time-use devices, such that contamination is no longer the concern. It contains a suspending micromembrane located along a microchannel. Under a steady driving pressure, the membrane displacement is a function of viscosity of the liquid sample being tested. We derived a simple analytical relation and perform a simulation for converting the membrane displacement to the sample viscosity. We conducted experiments with liquids (water and mineral oil) with defined properties to verify such a relation. We further applied the micro-viscometer to measure bovine blood samples with different hematocrit levels. It can be concluded that the microfluidic viscometer has a high compatibility with a broad range of biomedical applications. Full article

(This article belongs to the Section E：Engineering and Technology)

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19 pages, 10247 KiB

Open AccessArticle

Performance Evaluation of a Piezoelectric Energy Harvester Based on Flag-Flutter

by Hassan Elahi, Marco Eugeni, Federico Fune, Luca Lampani, Franco Mastroddi, Giovanni Paolo Romano and Paolo Gaudenzi

Micromachines 2020, 11(10), 933; https://doi.org/10.3390/mi11100933 - 14 Oct 2020

Cited by 35 | Viewed by 3362

Abstract

In the last few decades, piezoelectric (PZT) materials have played a vital role in the aerospace industry because of their energy harvesting capability. PZT energy harvesters (PEH) absorb the energy from an operational environment and can transform it into useful energy to drive [...] Read more.

In the last few decades, piezoelectric (PZT) materials have played a vital role in the aerospace industry because of their energy harvesting capability. PZT energy harvesters (PEH) absorb the energy from an operational environment and can transform it into useful energy to drive nano/micro-electronic components. In this research work, a PEH based on the flag-flutter mechanism is presented. This mechanism is based on fluid-structure interaction (FSI). The flag is subjected to the axial airflow in the subsonic wind tunnel. The performance evaluation of the harvester and aeroelastic analysis is investigated numerically and experimentally. A novel solution is presented to extract energy from Limit Cycle Oscillations (LCOs) phenomenon by means of PZT transduction. The PZT patch absorbs the flow-induced structural vibrations and transforms it into electrical energy. Furthermore, the optimal resistance and length of the flag is predicted to maximize the energy harvesting. Different configurations of flag i.e., with Aluminium (Al) patch and PZT patch for flutter mode vibration mode are studied numerically and experimentally. The bifurcation diagram is constructed for the experimental campaign for the flutter instability of a cantilevered flag in subsonic wind-tunnel. Moreover, the flutter boundary conditions are analysed for reduced critical velocity and frequency. The designed PZT energy harvester via flag-flutter mechanism is suitable for energy harvesting in aerospace engineering applications to drive wireless sensors. The maximum output power that can be generated from the designed harvester is 6.72 mW and the optimal resistance is predicted to be 0.33 M

Ω

. Full article

(This article belongs to the Special Issue Piezoelectric Nanogenerators for Micro-Energy and Self-Powered Sensors)

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16 pages, 4601 KiB

Open AccessArticle

Pulse-Type Influence on the Micro-EDM Milling Machinability of Si₃N₄–TiN Workpieces

by Valeria Marrocco, Francesco Modica, Vincenzo Bellantone, Valentina Medri and Irene Fassi

Micromachines 2020, 11(10), 932; https://doi.org/10.3390/mi11100932 - 13 Oct 2020

Cited by 25 | Viewed by 2586

Abstract

In this paper, the effect of the micro-electro discharge machining (EDM) milling machinability of Si₃N₄–TiN workpieces was investigated. The material removal rate (MRR) and tool wear rate (TWR) were analyzed in relation to discharge pulse types in order to [...] Read more.

In this paper, the effect of the micro-electro discharge machining (EDM) milling machinability of Si₃N₄–TiN workpieces was investigated. The material removal rate (MRR) and tool wear rate (TWR) were analyzed in relation to discharge pulse types in order to evaluate how the different pulse shapes impact on such micro-EDM performance indicators. Voltage and current pulse waveforms were acquired during micro-EDM trials, scheduled according to a Design of Experiment (DOE); then, a pulse discrimination algorithm was used to post-process the data off-line and discriminate the pulse types as short, arc, delayed, or normal. The analysis showed that, for the considered process parameter combinations, MRR was sensitive only to normal pulses, while the other pulse types had no remarkable effect on it. On the contrary, TWR was affected by normal pulses, but the occurrence of arcs and delayed pulses induced unexpected improvements in tool wear. Those results suggest that micro-EDM manufacturing of Si₃N₄–TiN workpiece is relevantly different from the micro-EDM process performed on metal workpieces such as steel. Additionally, the inspection of the Si₃N₄–TiN micro-EDM surface, performed by SEM and EDS analyses, showed the presence of re-solidified droplets and micro-cracks, which modified the chemical composition and the consequent surface quality of the machined micro-features. Full article

(This article belongs to the Special Issue Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications)

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24 pages, 5125 KiB

Open AccessArticle

Study of the Emergency Braking Test with an Autonomous Bus and the sEMG Neck Response by Means of a Low-Cost System

by Sergio Fuentes del Toro, Silvia Santos-Cuadros, Ester Olmeda and José Luis San Román

Micromachines 2020, 11(10), 931; https://doi.org/10.3390/mi11100931 - 13 Oct 2020

Cited by 5 | Viewed by 2420

Abstract

Nowadays, due to the advances and the increasing implementation of the autonomous braking systems in vehicles, the non-collision accident is expected to become more common than a crash when a sudden stop happens. The most common injury in this kind of accident is [...] Read more.

Nowadays, due to the advances and the increasing implementation of the autonomous braking systems in vehicles, the non-collision accident is expected to become more common than a crash when a sudden stop happens. The most common injury in this kind of accident is whiplash or cervical injury since the neck has high sensitivity to sharp deceleration. To date, biomechanical research has usually been developed inside laboratories and does not entirely represent real conditions (e.g., restraint systems or surroundings of the experiment). With the aim of knowing the possible neck effects and consequences of an automatic emergency braking inside an autonomous bus, a surface electromyography (sEMG) system built by low-cost elements and developed by us, in tandem with other devices, such as accelerometers or cameras, were used. Moreover, thanks to the collaboration of 18 participants, it was possible to study the non-collision effects in two different scenarios (braking test in which the passenger is seated and looking ahead while talking with somebody in front of him (BT1) and, a second braking test where the passenger used a smartphone (BT2) and nobody is seated in front of him talking to him). The aim was to assess the sEMG neck response in the most common situations when somebody uses some kind of transport in order to conclude which environments are riskier regarding a possible cervical injury. Full article

(This article belongs to the Special Issue Development of Innovative Sensor Platforms for Field Analysis)

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16 pages, 4327 KiB

Open AccessArticle

Toward an Ultra-Wideband Hybrid Metamaterial Based Microwave Absorber

by Aicha El Assal, Hanadi Breiss, Ratiba Benzerga, Ala Sharaiha, Akil Jrad and Ali Harmouch

Micromachines 2020, 11(10), 930; https://doi.org/10.3390/mi11100930 - 13 Oct 2020

Cited by 16 | Viewed by 3933

Abstract

In this paper, we propose a novel design of an ultra-wideband hybrid microwave absorber operating in the frequency range between 2 GHz and 18 GHz. This proposed hybrid absorber is composed of two different layers that integrate a multiband metamaterial absorber and a [...] Read more.

In this paper, we propose a novel design of an ultra-wideband hybrid microwave absorber operating in the frequency range between 2 GHz and 18 GHz. This proposed hybrid absorber is composed of two different layers that integrate a multiband metamaterial absorber and a lossy dielectric layer. The metamaterial absorber consists of a periodic pattern that is composed of an arrangement of different scales of coupled resonators and a metallic ground plane, and the dielectric layer is made of epoxy foam composite loaded with low weight percentage (0.075 wt.%) of 12 mm length carbon fibers. The numerical results show a largely expanded absorption bandwidth that ranges from 2.6 GHz to 18 GHz with incident angles between 0° and 45° and for both transverse electric and transverse magnetic waves. The measurements confirm that absorption of this hybrid based metamaterial absorber exceeds 90% within the above-mentioned frequency range and it may reach an absorption rate of 99% for certain frequency ranges. The proposed idea offers a further step in developing new electromagnetic absorbers, which will impact a broad range of applications. Full article

(This article belongs to the Special Issue Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications)

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19 pages, 2427 KiB

Open AccessReview

Ultrasonic Retinal Neuromodulation and Acoustic Retinal Prosthesis

by Pei-An Lo, Kyana Huang, Qifa Zhou, Mark S. Humayun and Lan Yue

Micromachines 2020, 11(10), 929; https://doi.org/10.3390/mi11100929 - 13 Oct 2020

Cited by 9 | Viewed by 4754

Abstract

Ultrasound is an emerging method for non-invasive neuromodulation. Studies in the past have demonstrated that ultrasound can reversibly activate and inhibit neural activities in the brain. Recent research shows the possibility of using ultrasound ranging from 0.5 to 43 MHz in acoustic frequency [...] Read more.

Ultrasound is an emerging method for non-invasive neuromodulation. Studies in the past have demonstrated that ultrasound can reversibly activate and inhibit neural activities in the brain. Recent research shows the possibility of using ultrasound ranging from 0.5 to 43 MHz in acoustic frequency to activate the retinal neurons without causing detectable damages to the cells. This review recapitulates pilot studies that explored retinal responses to the ultrasound exposure, discusses the advantages and limitations of the ultrasonic stimulation, and offers an overview of engineering perspectives in developing an acoustic retinal prosthesis. For comparison, this article also presents studies in the ultrasonic stimulation of the visual cortex. Despite that, the summarized research is still in an early stage; ultrasonic retinal stimulation appears to be a viable technology that exhibits enormous therapeutic potential for non-invasive vision restoration. Full article

(This article belongs to the Special Issue Micro/Nanofabrication for Retinal Implants)

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42 pages, 14997 KiB

Open AccessFeature PaperEditor’s ChoiceReview

MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications

by Haoran Wang, Yifei Ma, Hao Yang, Huabei Jiang, Yingtao Ding and Huikai Xie

Micromachines 2020, 11(10), 928; https://doi.org/10.3390/mi11100928 - 12 Oct 2020

Cited by 30 | Viewed by 8900

Abstract

Photoacoustic imaging (PAI) is drawing extensive attention and gaining rapid development as an emerging biomedical imaging technology because of its high spatial resolution, large imaging depth, and rich optical contrast. PAI has great potential applications in endoscopy, but the progress of endoscopic PAI [...] Read more.

Photoacoustic imaging (PAI) is drawing extensive attention and gaining rapid development as an emerging biomedical imaging technology because of its high spatial resolution, large imaging depth, and rich optical contrast. PAI has great potential applications in endoscopy, but the progress of endoscopic PAI was hindered by the challenges of manufacturing and assembling miniature imaging components. Over the last decade, microelectromechanical systems (MEMS) technology has greatly facilitated the development of photoacoustic endoscopes and extended the realm of applicability of the PAI. As the key component of photoacoustic endoscopes, micromachined ultrasound transducers (MUTs), including piezoelectric MUTs (pMUTs) and capacitive MUTs (cMUTs), have been developed and explored for endoscopic PAI applications. In this article, the recent progress of pMUTs (thickness extension mode and flexural vibration mode) and cMUTs are reviewed and discussed with their applications in endoscopic PAI. Current PAI endoscopes based on pMUTs and cMUTs are also introduced and compared. Finally, the remaining challenges and future directions of MEMS ultrasound transducers for endoscopic PAI applications are given. Full article

(This article belongs to the Special Issue MEMS for Ultrasound)

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9 pages, 2124 KiB

Open AccessArticle

Printed Soft Sensor with Passivation Layers for the Detection of Object Slippage by a Robotic Gripper

by Reo Miura, Tomohito Sekine, Yi-Fei Wang, Jinseo Hong, Yushi Watanabe, Keita Ito, Yoshinori Shouji, Yasunori Takeda, Daisuke Kumaki, Fabrice Domingues Dos Santos, Atsushi Miyabo and Shizuo Tokito

Micromachines 2020, 11(10), 927; https://doi.org/10.3390/mi11100927 - 08 Oct 2020

Cited by 5 | Viewed by 3322

Abstract

Tactile sensing, particularly the detection of object slippage, is required for skillful object handling by robotic grippers. The real-time measurement and identification of the dynamic shear forces that result from slippage events are crucial for slip detection and effective object interaction. In this [...] Read more.

Tactile sensing, particularly the detection of object slippage, is required for skillful object handling by robotic grippers. The real-time measurement and identification of the dynamic shear forces that result from slippage events are crucial for slip detection and effective object interaction. In this study, a ferroelectric polymer-based printed soft sensor for object slippage detection was developed and fabricated by screen printing. The proposed sensor demonstrated a sensitivity of 8.2 μC·cm⁻² and was responsive to shear forces applied in both the parallel and perpendicular directions. An amplifier circuit, based on a printed organic thin-film transistor, was applied and achieved a high sensitivity of 0.1 cm²/V·s. Therefore, this study experimentally demonstrates the effectiveness of the proposed printable high-sensitivity tactile sensor, which could serve as part of a wearable robotic e-skin. The sensor could facilitate the production of a system to detect and prevent the slippage of objects from robotic grippers. Full article

(This article belongs to the Special Issue FET and Field Effect-Based Sensors)

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14 pages, 4679 KiB

Open AccessArticle

Surface Characterization and Tribological Performance Analysis of Electric Discharge Machined Duplex Stainless Steel

by Timur Rizovich Ablyaz, Evgeny Sergeevich Shlykov, Karim Ravilevich Muratov, Amit Mahajan, Gurpreet Singh, Sandeep Devgan and Sarabjeet Singh Sidhu

Micromachines 2020, 11(10), 926; https://doi.org/10.3390/mi11100926 - 07 Oct 2020

Cited by 25 | Viewed by 3180

Abstract

The present article focused on the surface characterization of electric discharge machined duplex stainless steel (DSS-2205) alloy with three variants of electrode material (Graphite, Copper-Tungsten and Tungsten electrodes). Experimentation was executed as per Taguchi L18 orthogonal array to inspect the influence of electric [...] Read more.

The present article focused on the surface characterization of electric discharge machined duplex stainless steel (DSS-2205) alloy with three variants of electrode material (Graphite, Copper-Tungsten and Tungsten electrodes). Experimentation was executed as per Taguchi L18 orthogonal array to inspect the influence of electric discharge machining (EDM) parameters on the material removal rate and surface roughness. The results revealed that the discharge current (contribution: 45.10%), dielectric medium (contribution: 18.24%) majorly affects the material removal rate, whereas electrode material (contribution: 38.72%), pulse-on-time (contribution: 26.11%) were the significant parameters affecting the surface roughness. The machined surface at high spark energy in EDM oil portrayed porosity, oxides formation, and intermetallic compounds. Moreover, a pin-on-disc wear analysis was executed and the machined surface exhibits 70% superior wear resistance compared to the un-machined sample. The surface thus produced also exhibited improved surface wettability responses. The outcomes depict that EDMed DSS alloy can be considered in the different biomedical and industrial applications. Full article

(This article belongs to the Special Issue Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications)

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15 pages, 4573 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Scalable and Low Stress Post-CMOS Processing Technique for Implantable Microsensors

by Ah-Hyoung Lee, Jihun Lee, Farah Laiwalla, Vincent Leung, Jiannan Huang, Arto Nurmikko and Yoon-Kyu Song

Micromachines 2020, 11(10), 925; https://doi.org/10.3390/mi11100925 - 05 Oct 2020

Cited by 13 | Viewed by 4795

Abstract

Implantable active electronic microchips are being developed as multinode in-body sensors and actuators. There is a need to develop high throughput microfabrication techniques applicable to complementary metal–oxide–semiconductor (CMOS)-based silicon electronics in order to process bare dies from a foundry to physiologically compatible implant [...] Read more.

Implantable active electronic microchips are being developed as multinode in-body sensors and actuators. There is a need to develop high throughput microfabrication techniques applicable to complementary metal–oxide–semiconductor (CMOS)-based silicon electronics in order to process bare dies from a foundry to physiologically compatible implant ensembles. Post-processing of a miniature CMOS chip by usual methods is challenging as the typically sub-mm size small dies are hard to handle and not readily compatible with the standard microfabrication, e.g., photolithography. Here, we present a soft material-based, low chemical and mechanical stress, scalable microchip post-CMOS processing method that enables photolithography and electron-beam deposition on hundreds of micrometers scale dies. The technique builds on the use of a polydimethylsiloxane (PDMS) carrier substrate, in which the CMOS chips were embedded and precisely aligned, thereby enabling batch post-processing without complication from additional micromachining or chip treatments. We have demonstrated our technique with 650 μm × 650 μm and 280 μm × 280 μm chips, designed for electrophysiological neural recording and microstimulation implants by monolithic integration of patterned gold and PEDOT:PSS electrodes on the chips and assessed their electrical properties. The functionality of the post-processed chips was verified in saline, and ex vivo experiments using wireless power and data link, to demonstrate the recording and stimulation performance of the microscale electrode interfaces. Full article

(This article belongs to the Special Issue Implantable Neural Sensors for the Brain Machine Interface)

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14 pages, 3749 KiB

Open AccessArticle

Experimental Study on the Minimum Undeformed Chip Thickness Based on Effective Rake Angle in Micro Milling

by Xian Wu, Li Liu, Mingyang Du, Jianyun Shen, Feng Jiang, Yuan Li and Yiyang Lin

Micromachines 2020, 11(10), 924; https://doi.org/10.3390/mi11100924 - 05 Oct 2020

Cited by 13 | Viewed by 2783

Abstract

Micro milling is widely used to manufacture micro parts due to its obvious advantages. The minimum undeformed chip thickness, the effective rake angle, and size effect are the typical characteristics and closely related to each other in micro milling. In this paper, the [...] Read more.

Micro milling is widely used to manufacture micro parts due to its obvious advantages. The minimum undeformed chip thickness, the effective rake angle, and size effect are the typical characteristics and closely related to each other in micro milling. In this paper, the averaging method is proposed to quantitatively estimate the effective rake angle in the cutting process. The minimum undeformed chip thickness is explained based on the effective rake angle and determined to be 0.17 r_n (tool cutting edge radius). Then, micro milling experiment was conducted to study the effect of the minimum undeformed chip thickness. It is found that the minimum undeformed chip thickness results in the unstable cutting process, the uneven peaks on cutting force signal, and the dense characteristic frequency distribution on frequency domain signal. The dominant ploughing effect induces the great specific cutting energy and the deteriorated surface roughness due to the minimum undeformed chip thickness. Full article

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18 pages, 3455 KiB

Open AccessArticle

Water-Gated Transistor Using Ion Exchange Resin for Potentiometric Fluoride Sensing

by Zahrah Alqahtani, Nawal Alghamdi, Thomas J. Robshaw, Robert Dawson, Mark D. Ogden, Alastair Buckely and Martin Grell

Micromachines 2020, 11(10), 923; https://doi.org/10.3390/mi11100923 - 05 Oct 2020

Cited by 4 | Viewed by 2752

Abstract

We introduce fluoride-selective anion exchange resin sorbents as sensitisers into membranes for water-gated field effect transistors (WGTFTs). Sorbents were prepared via metal (La or Al)-loading of a commercial macroporous aminophosphonic acid resin, Puromet^TM MTS9501, and were filled into a plasticised poly(vinyl chloride) [...] Read more.

We introduce fluoride-selective anion exchange resin sorbents as sensitisers into membranes for water-gated field effect transistors (WGTFTs). Sorbents were prepared via metal (La or Al)-loading of a commercial macroporous aminophosphonic acid resin, Puromet^TM MTS9501, and were filled into a plasticised poly(vinyl chloride) (PVC) phase transfer membrane. We found a potentiometric response (membrane potential leading to WGTFT threshold shift) to fluoride following a Langmuir–Freundlich (LF) adsorption isotherm with saturated membrane potential up to ~480 mV, extremely low characteristic concentration c_1/2 = 1/K, and picomolar limit of detection (LoD), even though ion exchange did not build up charge on the resin. La-loading gave a superior response compared to Al-loading. Membrane potential characteristics were distinctly different from charge accumulating sensitisers (e.g., organic macrocycles) but similar to the Cs⁺ (cation) selective ion-exchanging zeolite mineral ‘mordenite’. We propose a mechanism for the observed threshold shift and investigate interference from co-solutes. Strong interference from carbonate was brought under control by ‘diluting’ metal loading in the resin. This work sets a template for future studies using an entirely new ‘family’ of sensitisers in applications where very low limit of detection is essential such as for ions of arsenic, mercury, copper, palladium, and gold. Full article

(This article belongs to the Special Issue FET and Field Effect-Based Sensors)

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10 pages, 4545 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Micropillar/Microwell Chip Assessment for Detoxification of Bisphenol A with Korean Pear (Pyrus pyrifolia)

by Dong Woo Lee, Moo-Yeal Lee, Sukkil Koh and Mihi Yang

Micromachines 2020, 11(10), 922; https://doi.org/10.3390/mi11100922 - 03 Oct 2020

Cited by 6 | Viewed by 3701

Abstract

A micropillar/microwell chip platform with 3D cultured liver cells has been used for HTP screening of hepatotoxicity of bisphenol A (BPA), an endocrine-disrupting chemical. We previously found the hepatotoxicity of BPA is alleviated by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase 2 (ALDH2). In [...] Read more.

A micropillar/microwell chip platform with 3D cultured liver cells has been used for HTP screening of hepatotoxicity of bisphenol A (BPA), an endocrine-disrupting chemical. We previously found the hepatotoxicity of BPA is alleviated by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase 2 (ALDH2). In this study, we have tested potential BPA detoxification with Korean pear (Pyrus pyrifolia) extract, stimulators of ADH and ALDH, as well as arbutin, a reference compound in the pears, on the micropillar/microwell chip platform with human liver cells. Surprisingly, the toxicity of BPA was reduced in the presence of Korean pear extract, indicated by significantly increased IC₅₀ values. The IC₅₀ value of BPA with Korean pear extract tested against HepG2 cells was shifted from 151 to 451 μM, whereas those tested against Hep3B cells was shifted from 110 to 204 μM. Among the tested various concentrations, 1.25, 2.5, and 5 mg/mL of the extract significantly reduced BPA toxicity (Ps < 0.05). However, there was no such detoxification effects with arbutin. This result was supported by changes in protein levels of ADH in the liver cells. Full article

(This article belongs to the Special Issue Lab-on-a-Chip Systems for Toxicology)

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21 pages, 5429 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Acoustic Microfluidic Separation Techniques and Bioapplications: A Review

by Yuan Gao, Mengren Wu, Yang Lin and Jie Xu

Micromachines 2020, 11(10), 921; https://doi.org/10.3390/mi11100921 - 02 Oct 2020

Cited by 67 | Viewed by 8138

Abstract

Microfluidic separation technology has garnered significant attention over the past decade where particles are being separated at a micro/nanoscale in a rapid, low-cost, and simple manner. Amongst a myriad of separation technologies that have emerged thus far, acoustic microfluidic separation techniques are extremely [...] Read more.

Microfluidic separation technology has garnered significant attention over the past decade where particles are being separated at a micro/nanoscale in a rapid, low-cost, and simple manner. Amongst a myriad of separation technologies that have emerged thus far, acoustic microfluidic separation techniques are extremely apt to applications involving biological samples attributed to various advantages, including high controllability, biocompatibility, and non-invasive, label-free features. With that being said, downsides such as low throughput and dependence on external equipment still impede successful commercialization from laboratory-based prototypes. Here, we present a comprehensive review of recent advances in acoustic microfluidic separation techniques, along with exemplary applications. Specifically, an inclusive overview of fundamental theory and background is presented, then two sets of mechanisms underlying acoustic separation, bulk acoustic wave and surface acoustic wave, are introduced and discussed. Upon these summaries, we present a variety of applications based on acoustic separation. The primary focus is given to those associated with biological samples such as blood cells, cancer cells, proteins, bacteria, viruses, and DNA/RNA. Finally, we highlight the benefits and challenges behind burgeoning developments in the field and discuss the future perspectives and an outlook towards robust, integrated, and commercialized devices based on acoustic microfluidic separation. Full article

(This article belongs to the Special Issue Microfluidic Sensors II)

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