Editorial

2 pages, 150 KiB

Open AccessEditorial

Editorial for the Special Issue on Biosensors and MEMS-Based Diagnostic Applications

by Zeynep Altintas

Micromachines 2021, 12(3), 229; https://doi.org/10.3390/mi12030229 - 25 Feb 2021

Cited by 1 | Viewed by 1680

Biosensors and micro-electromechanical systems (MEMS) have witnessed rapid development and enormous interest over the past decades [...] Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

Research

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12 pages, 6307 KiB

Open AccessArticle

Wearable Contact Lens Sensor for Non-Invasive Continuous Monitoring of Intraocular Pressure

by Zhiqiang Dou, Jun Tang, Zhiduo Liu, Qigong Sun, Yang Wang, Yamin Li, Miao Yuan, Huijuan Wu, Yijun Wang, Weihua Pei and Hongda Chen

Micromachines 2021, 12(2), 108; https://doi.org/10.3390/mi12020108 - 22 Jan 2021

Cited by 16 | Viewed by 4650

Abstract

Intraocular pressure (IOP) is an essential indicator of the diagnosis and treatment of glaucoma. IOP has an apparent physiological rhythm, and it often reaches its peak value at night. To avoid missing the peak value at night and sample the entire rhythm cycle, [...] Read more.

Intraocular pressure (IOP) is an essential indicator of the diagnosis and treatment of glaucoma. IOP has an apparent physiological rhythm, and it often reaches its peak value at night. To avoid missing the peak value at night and sample the entire rhythm cycle, the continuous monitoring of IOP is urgently needed. A wearable contact lens IOP sensor based on a platinum (Pt) strain gauge is fabricated by the micro-electro-mechanical (MEMS) process. The structure and parameters of the strain gauge are optimized to improve the sensitivity and temperature stability. Tests on an eyeball model indicate that the IOP sensor has a high sensitivity of 289.5 μV/mmHg and excellent dynamic cycling performance at different speeds of IOP variation. The temperature drift coefficient of the sensor is 33.4 μV/°C. The non-invasive IOP sensor proposed in this report exhibits high sensitivity and satisfactory stability, promising a potential in continuous IOP monitoring. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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14 pages, 878 KiB

Open AccessArticle

Geometric Understanding of Local Fluctuation Distribution of Conduction Time in Lined-Up Cardiomyocyte Network in Agarose-Microfabrication Multi-Electrode Measurement Assay

by Kazufumi Sakamoto, Shota Aoki, Yuhei Tanaka, Kenji Shimoda, Yoshitsune Hondo and Kenji Yasuda

Micromachines 2020, 11(12), 1105; https://doi.org/10.3390/mi11121105 - 14 Dec 2020

Cited by 3 | Viewed by 2083

Abstract

We examined characteristics of the propagation of conduction in width-controlled cardiomyocyte cell networks for understanding the contribution of the geometrical arrangement of cardiomyocytes for their local fluctuation distribution. We tracked a series of extracellular field potentials of linearly lined-up human embryonic stem (ES) [...] Read more.

We examined characteristics of the propagation of conduction in width-controlled cardiomyocyte cell networks for understanding the contribution of the geometrical arrangement of cardiomyocytes for their local fluctuation distribution. We tracked a series of extracellular field potentials of linearly lined-up human embryonic stem (ES) cell-derived cardiomyocytes and mouse primary cardiomyocytes with 100 kHz sampling intervals of multi-electrodes signal acquisitions and an agarose microfabrication technology to localize the cardiomyocyte geometries in the lined-up cell networks with 100–300 μm wide agarose microstructures. Conduction time between two neighbor microelectrodes (300 μm) showed Gaussian distribution. However, the distributions maintained their form regardless of its propagation distances up to 1.5 mm, meaning propagation diffusion did not occur. In contrast, when Quinidine was applied, the propagation time distributions were increased as the faster firing regulation simulation predicted. The results indicate the “faster firing regulation” is not sufficient to explain the conservation of the propagation time distribution in cardiomyocyte networks but should be expanded with a kind of community effect of cell networks, such as the lower fluctuation regulation. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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16 pages, 3906 KiB

Open AccessArticle

An Approach to Ring Resonator Biosensing Assisted by Dielectrophoresis: Design, Simulation and Fabrication

by Anders Henriksson, Laura Kasper, Matthias Jäger, Peter Neubauer and Mario Birkholz

Micromachines 2020, 11(11), 954; https://doi.org/10.3390/mi11110954 - 22 Oct 2020

Cited by 12 | Viewed by 4287

Abstract

The combination of extreme miniaturization with a high sensitivity and the potential to be integrated in an array form on a chip has made silicon-based photonic microring resonators a very attractive research topic. As biosensors are approaching the nanoscale, analyte mass transfer and [...] Read more.

The combination of extreme miniaturization with a high sensitivity and the potential to be integrated in an array form on a chip has made silicon-based photonic microring resonators a very attractive research topic. As biosensors are approaching the nanoscale, analyte mass transfer and bonding kinetics have been ascribed as crucial factors that limit their performance. One solution may be a system that applies dielectrophoretic forces, in addition to microfluidics, to overcome the diffusion limits of conventional biosensors. Dielectrophoresis, which involves the migration of polarized dielectric particles in a non-uniform alternating electric field, has previously been successfully applied to achieve a 1000-fold improved detection efficiency in nanopore sensing and may significantly increase the sensitivity in microring resonator biosensing. In the current work, we designed microring resonators with integrated electrodes next to the sensor surface that may be used to explore the effect of dielectrophoresis. The chip design, including two different electrode configurations, electric field gradient simulations, and the fabrication process flow of a dielectrohoresis-enhanced microring resonator-based sensor, is presented in this paper. Finite element method (FEM) simulations calculated for both electrode configurations revealed ∇E² values above 10¹⁷ V²m⁻³ around the sensing areas. This is comparable to electric field gradients previously reported for successful interactions with larger molecules, such as proteins and antibodies. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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15 pages, 4369 KiB

Open AccessArticle

Enhancement of the Start-Up Time for Microliter-Scale Microbial Fuel Cells (µMFCs) via the Surface Modification of Gold Electrodes

by Begüm Şen-Doğan, Meltem Okan, Nilüfer Afşar-Erkal, Ebru Özgür, Özge Zorlu and Haluk Külah

Micromachines 2020, 11(7), 703; https://doi.org/10.3390/mi11070703 - 21 Jul 2020

Cited by 3 | Viewed by 3138

Abstract

Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of [...] Read more.

Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of gold surface modification with different thiol molecules were investigated for their implementation as anode electrodes in micro-scale MFCs (µMFCs). Several double-chamber µMFCs with 10.4 µL anode and cathode chambers were fabricated using silicon-microelectromechanical systems (MEMS) fabrication technology. µMFC systems assembled with modified gold anodes were operated under anaerobic conditions with the continuous feeding of anolyte and catholyte to compare the effect of different thiol molecules on the biofilm formation of Shewanella oneidensis MR-1. Performances were evaluated using polarization curves, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microcopy (SEM). The results showed that µMFCs modified with thiol self-assembled monolayers (SAMs) (cysteamine and 11-MUA) resulted in more than a 50% reduction in start-up times due to better bacterial attachment on the anode surface. Both 11-MUA and cysteamine modifications resulted in dense biofilms, as observed in SEM images. The power output was found to be similar in cysteamine-modified and bare gold µMFCs. The power and current densities obtained in this study were comparable to those reported in similar studies in the literature. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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14 pages, 2233 KiB

Open AccessArticle

Design and Electrochemical Characterization of Spiral Electrochemical Notification Coupled Electrode (SENCE) Platform for Biosensing Application

by Abha Umesh Sardesai, Vikram Narayanan Dhamu, Anirban Paul, Sriram Muthukumar and Shalini Prasad

Micromachines 2020, 11(3), 333; https://doi.org/10.3390/mi11030333 - 24 Mar 2020

Cited by 27 | Viewed by 4874

Abstract

C-reactive protein (CRP) is considered to be an important biomarker associated with many diseases. During any physiological inflammation, the level of CRP reaches its peak at 48 h, whereas its half-life is around 19 h. Hence, the detection of low-level CRP is an [...] Read more.

C-reactive protein (CRP) is considered to be an important biomarker associated with many diseases. During any physiological inflammation, the level of CRP reaches its peak at 48 h, whereas its half-life is around 19 h. Hence, the detection of low-level CRP is an important task for the prognostic management of diseases like cancer, stress, metabolic disorders, cardiovascular diseases, and so on. There are various techniques available in the market to detect low-level CRP like ELISA, Western blot, etc. An electrochemical biosensor is one of the important miniaturized platforms which provides sensitivity along with ease of operation. The most important element of an electrochemical biosensor platform is the electrode which, upon functionalization with a probe, captures the selective antibody–antigen interaction and produces a digital signal in the form of potential/current. Optimization of the electrode design can increase the sensitivity of the sensor by 5–10-fold. Herein, we come up with a new sensor design called the spiral electrochemical notification coupled electrode (SENCE) where the working electrode (WE) is concentric in nature, which shows better response than the market-available standard screen-printed electrode. The sensor is thoroughly characterized using a standard Ferro/Ferri couple. The sensing performance of the fabricated platform is also characterized by the detection of standard H₂O₂ using a diffusion-driven technique, and a low detection limit of 15 µM was achieved. Furthermore, we utilized the platform to detect a low level (100 ng/mL) of CRP in synthetic sweat. The manuscript provides emphasis on the design of a sensor that can offer good sensitivity in electrochemical biosensing applications. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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8 pages, 2313 KiB

Open AccessArticle

Fabrication of a Bare Optical Fiber-Based Biosensor

by Yu-Jun Zhang, Jin-Cherng Hsu, Jia-Huey Tsao and Yung-Shin Sun

Micromachines 2019, 10(8), 522; https://doi.org/10.3390/mi10080522 - 08 Aug 2019

Cited by 5 | Viewed by 2504

Abstract

A bare optical fiber-based biosensor is proposed for measuring the refractive index of different liquids and the binding kinetics of biomolecules to the sensor surface. This optical fiber sensor is based on the Kretschmann’s configuration to attain total internal reflection (TIR) for surface [...] Read more.

A bare optical fiber-based biosensor is proposed for measuring the refractive index of different liquids and the binding kinetics of biomolecules to the sensor surface. This optical fiber sensor is based on the Kretschmann’s configuration to attain total internal reflection (TIR) for surface plasmon resonance (SPR) excitation. One end of the bare optical fiber is coated with a gold film. By guiding the light source from the other end into the optical fiber, the light is reflected from the gold-deposited end and the surface evanescent wave is excited in the gold film-transparent material interface. Methanol and ethanol solutions with different refractive indices are used for measuring the corresponding changes in the peak values of the spectra and calculating the corresponding sensitivities. These values are experimentally determined to be in the order of 10⁻⁴~10⁻⁵ refractive index unit (RIU). Binding of proteins onto the sensor surface is also monitored in real time to obtain the binding kinetics. We believe that, in the future, this optical fiber sensor can serve as a useful biosensor for in situ measurement of allergens, antibody–antigen interactions, and even circulating tumor cells in the blood. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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Review

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36 pages, 8878 KiB

Open AccessReview

A Prominent Cell Manipulation Technique in BioMEMS: Dielectrophoresis

by Zeynep Çağlayan, Yağmur Demircan Yalçın and Haluk Külah

Micromachines 2020, 11(11), 990; https://doi.org/10.3390/mi11110990 - 03 Nov 2020

Cited by 28 | Viewed by 4433

Abstract

BioMEMS, the biological and biomedical applications of micro-electro-mechanical systems (MEMS), has attracted considerable attention in recent years and has found widespread applications in disease detection, advanced diagnosis, therapy, drug delivery, implantable devices, and tissue engineering. One of the most essential and leading goals [...] Read more.

BioMEMS, the biological and biomedical applications of micro-electro-mechanical systems (MEMS), has attracted considerable attention in recent years and has found widespread applications in disease detection, advanced diagnosis, therapy, drug delivery, implantable devices, and tissue engineering. One of the most essential and leading goals of the BioMEMS and biosensor technologies is to develop point-of-care (POC) testing systems to perform rapid prognostic or diagnostic tests at a patient site with high accuracy. Manipulation of particles in the analyte of interest is a vital task for POC and biosensor platforms. Dielectrophoresis (DEP), the induced movement of particles in a non-uniform electrical field due to polarization effects, is an accurate, fast, low-cost, and marker-free manipulation technique. It has been indicated as a promising method to characterize, isolate, transport, and trap various particles. The aim of this review is to provide fundamental theory and principles of DEP technique, to explain its importance for the BioMEMS and biosensor fields with detailed references to readers, and to identify and exemplify the application areas in biosensors and POC devices. Finally, the challenges faced in DEP-based systems and the future prospects are discussed. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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37 pages, 4817 KiB

Open AccessReview

Graphene Quantum Dots as Flourishing Nanomaterials for Bio-Imaging, Therapy Development, and Micro-Supercapacitors

by Merve Kortel, Bhargav D. Mansuriya, Nicole Vargas Santana and Zeynep Altintas

Micromachines 2020, 11(9), 866; https://doi.org/10.3390/mi11090866 - 18 Sep 2020

Cited by 50 | Viewed by 6827

Abstract

Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, [...] Read more.

Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, the quantum confinement and edge effects are giving GQDs their tremendous character, while their heteroatom doping attributes enable us to specifically and meritoriously tune their prospective characteristics for innumerable operations. Considering the substantial role offered by GQDs in the area of biomedicine and nanoscience, through this review paper, we primarily focus on their applications in bio-imaging, micro-supercapacitors, as well as in therapy development. The size-dependent aspects, functionalization, and particular utilization of the GQDs are discussed in detail with respect to their distinct nano-bio-technological applications. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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30 pages, 4179 KiB

Open AccessReview

DNA Microsystems for Biodiagnosis

by Alana Torres Vidal, Igor L. Medintz and Hieu Bui

Micromachines 2020, 11(4), 445; https://doi.org/10.3390/mi11040445 - 23 Apr 2020

Cited by 2 | Viewed by 5166

Abstract

Researchers are continuously making progress towards diagnosis and treatment of numerous diseases. However, there are still major issues that are presenting many challenges for current medical diagnosis. On the other hand, DNA nanotechnology has evolved significantly over the last three decades and is [...] Read more.

Researchers are continuously making progress towards diagnosis and treatment of numerous diseases. However, there are still major issues that are presenting many challenges for current medical diagnosis. On the other hand, DNA nanotechnology has evolved significantly over the last three decades and is highly interdisciplinary. With many potential technologies derived from the field, it is natural to begin exploring and incorporating its knowledge to develop DNA microsystems for biodiagnosis in order to help address current obstacles, such as disease detection and drug resistance. Here, current challenges in disease detection are presented along with standard methods for diagnosis. Then, a brief overview of DNA nanotechnology is introduced along with its main attractive features for constructing biodiagnostic microsystems. Lastly, suggested DNA-based microsystems are discussed through proof-of-concept demonstrations with improvement strategies for standard diagnostic approaches. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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