Harnessing flow-induced vibrations for energy harvesting: Experimental and numerical insights using piezoelectric transducer.

Flow-induced vibrations (FIV) were considered as unwanted vibrations analogous to noise. However, in a recent trend, the energy of these vibrations can be harvested and converted to electrical power. In this study, the potential of FIV as a source of renewable energy is highlighted through experimental and numerical analyses. The experimental study was conducted on an elastically mounted circular cylinder using helical and leaf springs in the wind tunnel. The Reynolds number (Re) varied between 2300-16000. The motion of the cylinder was restricted in all directions except the transverse direction. The micro-electromechanical system (MEMS) was mounted on the leaf spring to harvest the mechanical energy. Numerical simulations were also performed with SST k-ω turbulence model to supplement the experiments and were found to be in good agreement with the experimental results. The flow separation and vortex shedding induce aerodynamic forces in the cylinder causing it to vibrate. 2S vortex shedding pattern was observed in all of the cases in this study. The maximum dimensionless amplitude of vibration (A/D) obtained was 0.084 and 0.068 experimentally and numerically, respectively. The results showed that the region of interest is the lock-in region where maximum amplitude of vibration is observed and, therefore, the maximum power output. The piezoelectric voltage and power output were recorded for different reduced velocities (Ur = 1-10) at different resistance values in the circuit. It was observed that as the amplitude of oscillation of the cylinder increases, the voltage and power output of the MEMS increases due to high strain in piezoelectric transducer. The maximum output voltage of 0.6V was observed at Ur = 4.95 for an open circuit, i.e., for a circuit with the resistance value of infinity. As the resistance value reduced, a drop in voltage output was observed. Maximum power of 10.5µW was recorded at Ur = 4.95 for a circuit resistance of 100Ω.

A Hybrid Orbitrap-Nanoelectromechanical Systems Approach for the Analysis of Individual, Intact Proteins in Real Time.

Nanoelectromechanical systems (NEMS)-based mass spectrometry (MS) is an emerging technique that enables determination of the mass of individual adsorbed particles by driving nanomechanical devices at resonance and monitoring the real-time changes in their resonance frequencies induced by each single molecule adsorption event. We incorporate NEMS into an Orbitrap mass spectrometer and report our progress towards leveraging the single-molecule capabilities of the NEMS to enhance the dynamic range of conventional MS instrumentation and to offer new capabilities for performing deep proteomic analysis of clinically relevant samples. We use the hybrid instrument to deliver E. coli GroEL molecules (801 kDa) to the NEMS devices in their native, intact state. Custom ion optics are used to focus the beam down to 40 µm diameter with a maximum flux of 25 molecules/second. The mass spectrum obtained with NEMS-MS shows good agreement with the known mass of GroEL.

Pre-enrichment-free detection of hepatocellular carcinoma-specific ctDNA via PDMS and MEMS-based microfluidic sensor.

The growing interest in microfluidic biosensors has led to improvements in the analytical performance of various sensing mechanisms. Although various sensors can be integrated with microfluidics, electrochemical ones have been most commonly employed due to their ease of miniaturization, integration ability, and low cost, making them an established point-of-care diagnostic method. This concept can be easily adapted to the detection of biomarkers specific to certain cancer types. Pathological profiling of hepatocellular carcinoma (HCC) is heterogeneous and rather complex, and biopsy samples contain limited information regarding the tumor and do not reflect its heterogeneity. Circulating tumor DNAs (ctDNAs), which can contain information regarding cancer characteristics, have been studied tremendously since liquid biopsy emerged as a new diagnostic method. Recent improvements in the accuracy and sensitivity of ctDNA determination also paved the way for genotyping of somatic genomic alterations. In this study, three-electrode (Au-Pt-Ag) glass chips were fabricated and combined with polydimethylsiloxane (PDMS) microchannels to establish an electrochemical microfluidic sensor for detecting c.747G > T hotspot mutations in the TP53 gene of ctDNAs from HCC. The preparation and analysis times of the constructed sensor were as short as 2 h in total, and a relatively high flow rate of 30 µl/min was used during immobilization and hybridization steps. To the best of our knowledge, this is the first time a PDMS-based microfluidic electrochemical sensor has been developed to target HCC ctDNAs. The system exhibited a limit of detection (LOD) of 24.1 fM within the tested range of 2-200 fM. The sensor demonstrated high specificity in tests conducted with fully noncomplementary and one-base mismatched target sequences. The developed platform is promising for detecting HCC-specific ctDNA at very low concentrations without requiring pre-enrichment steps.

Thin-Film Piezoelectric Micromachined Ultrasound Transducers in Biomedical Applications: A Review.

Thin-film piezoelectric micromachined ultrasound transducers (PMUTs) are an increasingly relevant and well-researched field, and their biomedical importance has been growing as the technology continues to mature. This review article briefly discusses their history in biomedical use, provides a simple explanation of their principles for newer readers, and sheds light on the materials selection for these devices. Primarily, it discusses the significant applications of PMUTs in the biomedical industry and showcases recent progress that has been made in each application. The biomedical applications covered include common historical uses of ultrasound such as ultrasound imaging, ultrasound therapy, and fluid sensing, but additionally new and upcoming applications such as drug delivery, photoacoustic imaging, thermoacoustic imaging, biometrics, and intrabody communication. By including a device comparison chart for different applications, this review aims to assist microelectromechanical systems (MEMS) designers that work with PMUTs by providing a benchmark for recent research works. Furthermore, it puts forth a discussion on the current challenges being faced by PMUTs in the biomedical field, current and likely future research trends, and opportunities for PMUT development areas, as well as sharing the opinions and predictions of the authors on the state of this technology as a whole. The review aims to be a comprehensive introduction to these topics without diving excessively deep into existing literature.

Multisensor Integrated Platform Based on MEMS Charge Variation Sensing Technology for Biopotential Acquisition.

We propose a new methodology for long-term biopotential recording based on an MEMS multisensor integrated platform featuring a commercial electrostatic charge-transfer sensor. This family of sensors was originally intended for presence tracking in the automotive industry, so the existing setup was engineered for the acquisition of electrocardiograms, electroencephalograms, electrooculograms, and electromyography, designing a dedicated front-end and writing proper firmware for the specific application. Systematic tests on controls and nocturnal acquisitions from patients in a domestic environment will be discussed in detail. The excellent results indicate that this technology can provide a low-power, unexplored solution to biopotential acquisition. The technological breakthrough is in that it enables adding this type of functionality to existing MEMS boards at near-zero additional power consumption. For these reasons, it opens up additional possibilities for wearable sensors and strengthens the role of MEMS technology in medical wearables for the long-term synchronous acquisition of a wide range of signals.

An electromechanical stimulation regulating model with flexoelectric effect of piezoelectric laminated micro-beam for cell bionic culture.

Cell bionic culture requires the construction of cell growth microenvironments. In this paper, mechanical force and electrical stimulations are applied to the cells cultured on the surface of the piezoelectric laminated micro-beam driven by an excitation voltage. Based on the extended dielectric theory, the electromechanical microenvironment regulating model of the current piezoelectric laminated micro-beam is established. The variational principle is used to obtain the governing equations and boundary conditions. The differential quadrature method and the iterative method are used to solve two boundary value problems for cantilever beams and simply supported beams. In two cases, the mechanical force and electrical stimulations applied to the cells are analyzed in detail and the microscale effect is investigated. This study is meaningful for improving the quality of cell culture and promoting the cross-integration of mechanics and biomedicine.

MEMS Fingertip Strain Plethysmography for Cuffless Estimation of Blood Pressure.

OBJECTIVE: To develop a cuffless method for estimating blood pressure (BP) from fingertip strain plethysmography (SPG) recordings. METHODS: A custom-built micro-electromechanical systems (MEMS) strain sensor is employed to record heartbeat-induced vibrations at the fingertip. An XGboost regressor is then trained to relate SPG recordings to beat-to-beat systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP) values. For this purpose, each SPG segment in this setup is represented by a feature vector consisting of cardiac time interval, amplitude features, statistical properties, and demographic information of the subjects. In addition, a novel concept, coined geometric features, are introduced and incorporated into the feature space to further encode the dynamics in SPG recordings. The performance of the regressor is assessed on 32 healthy subjects through 5-fold cross-validation (5-CV) and leave-subject-out cross validation (LSOCV). RESULTS: Mean absolute errors (MAEs) of 3.88 mmHg and 5.45 mmHg were achieved for DBP and SBP estimations, respectively, in the 5-CV setting. LSOCV yielded MAEs of 8.16 mmHg for DBP and 16.81 mmHg for SBP. Through feature importance analysis, 3 geometric and 26 integral-related features introduced in this work were identified as primary contributors to BP estimation. The method exhibited robustness against variations in blood pressure level (normal to critical) and body mass index (underweight to obese), with MAE ranges of [1.28, 4.28] mmHg and [2.64, 7.52] mmHg, respectively. CONCLUSION: The findings suggest high potential for SPG-based BP estimation at the fingertip. SIGNIFICANCE: This study presents a fundamental step towards the augmentation of optical sensors that are susceptible to dark skin tones.

MEMS strapdown inertial attitude measurement system using rotational modulation technology.

Attitude determination involves the integration of methodologies and systems for estimating the time varying attitude of moving objects. Strapdown Inertial Attitude Measurement System (SIAMS) is among the most widely used navigation systems. The development of cost effective Micro Electro Mechanic System (MEMS) based inertial sensors has made attitude measurement system more affordable. However, MEMS sensors suffer from various errors that have to be calibrated and compensated to get acceptable attitude results. Given the auto-compensation of inertial sensor bias in rotation error modulation, the objective of this paper is to develop a MEMS-based rotary SIAMS, in which the significant sensor bias is automatically compensated by rotating the IMU, to offer comparable performance with respect to a tactical-grade Inertial Measurement Unit (IMU). With the analysis of the relationship between the MEMS error and misalignment, a MEMS calibration model is derived, and a combined calibration method of multi position rotation is applied to estimate the deterministic sensor errors such as bias, scale factor, and misalignment. Simulation and experiment results indicate that the proposed method can further modulate and compensate the MEMS errors, thereby improving the MEMS attitude accuracy.

Representing Fine Texture of Pencil Hardness by High-Frequency Vibrotactile Equivalence Conversion Using Ultra-Thin PZT-MEMS Vibrators.

This study aims to represent fine texture differences in pencil hardness using intensity segment modulation (ISM), a sensory equivalent conversion method of vibration from high to low frequencies. This method enables the presentation of delicate tactile sensations even with small transducers. We integrated this approach in the world's thinnest ultra-thin PZT-MEMS vibrator with a stylus-type device. The vibration waveforms of four types of pencil hardness were captured under the same conditions, and the differences in the frequency components were confirmed. We compared the fine texture feelings under raw signal, ISM, and ISM below 1 kHz conditions by conducting discrimination tests and subjective similarity evaluations. The results showed that ISM could reproduce similar feelings of the pencil hardness.

Ultrasensitive detection of vital biomolecules based on a multi-purpose BioMEMS for Point of care testing: digoxin measurement as a case study.

Rapid and label-free detection of very low concentrations of biomarkers in disease diagnosis or therapeutic drug monitoring is essential to prevent disease progression in Point of Care Testing. For this purpose, we propose a multi-purpose optical Bio-Micro-Electro-Mechanical-System (BioMEMS) sensing platform which can precisely measure very small changes of biomolecules concentrations in plasma-like buffer samples. This is realized by the development of an interferometric detection method on highly sensitive MEMS transducers (cantilevers). This approach facilitates the precise analysis of the obtained results to determine the analyte type and its concentrations. Furthermore, the proposed multi-purpose platform can be used for a wide range of biological assessments in various concentration levels by the use of an appropriate bioreceptor and the control of its coating density on the cantilever surface. In this study, the present system is prepared for the identification of digoxin medication in its therapeutic window for therapeutic drug monitoring as a case study. The experimental results represent the repeatability and stability of the proposed device as well as its capability to detect the analytes in less than eight minutes for all samples. In addition, according to the experiments carried out for very low concentrations of digoxin in plasma-like buffer, the detection limit of LOD = 300 fM and the maximum sensitivity of S = 5.5 × 1012 AU/M are achieved for the implemented biosensor. The present ultrasensitive multi-purpose BioMEMS sensor can be a fully-integrated, cost-effective device to precisely analyze various biomarker concentrations for various biomedical applications.

Analysis of the technical feasibility of using artificial intelligence for smoothing active power in a photovoltaic system connected to the power system

Abstract Recent technological advances and increased participation of energy systems based on photovoltaic solar energy place this renewable energy source in a prominent position in the current scenario. With the increase in the share of solar photovoltaic systems, the impact of power fluctuations in these sources has worsened, which can affect the quality of electrical energy and the reliability of the electrical power system. Therefore, with the use of energy storage together with control algorithms based on artificial intelligence, it is possible to control and perform power smoothing. In this context, the study presents a technical feasibility study on the use of artificial neural network (ANN) to perform the power smoothing of the photovoltaic system connected to the network. Being studied the performance of a real photovoltaic system operating in conjunction with an ideal energy storage for comparative analysis of the performance of the artificial neural network when the numbers of neurons and layers are modified for different real operating conditions considered as temperature variation, humidity, irradiation, pressure and wind speed, which are considered to be ANN input data. The results obtained point to the feasibility of using ANN, with acceptable precision, for power smoothing. According to the analyzes carried out, it is clear that ANN's with few neurons, the smoothing profile tends to be more accurate when compared to larger amounts of neurons. In the current state of the study, it was not possible to determine a relationship between the variations in the number of neurons with the most accurate results, it is important to note that the development of the curve pointed by the neural network can be influenced by the database. It should be noted that, when ANN exceeds or does not reach the optimal smoothing curve, the storage system compensates for the lack or excess of power, and there is a need for other mechanisms to optimize power smoothing.

Determination of the increased risk of developing atrial fibrillation in fibromyalgia syndrome

Abstract Introduction: Atrial fibrillation (AF) is the leading cause of ischemic stroke and is one of the most common arrhythmias. Previous studies have shown that impaired diastolic functions, P wave dispersion (Pd), and prolonged atrial conduction times (ACT) are associated with increased incidence of atrial fibrillation (AF). The aim of this study was to evaluate diastolic functions, Pd, and ACT in fibromyalgia syndrome (FMS) patients to determine whether there is an increase in the risk of developing AF. Methods: The study included a total of 140 female patients (70 FMS group, 70 healthy control group). Pd was evaluated using 12 lead electrocardiography (ECG), and diastolic functions and ACT with echocardiography. The ECG and echocardiographic evaluations were performed by different cardiologists blinded to the clinical information of the subjects. Results: There was no difference between the two groups in laboratory and clinical parameters. Patients with FMS had significantly higher echocardiographic parameters of ACT known as left-sided intra-atrial (13.9 ± 5.9 vs. 8.1 ± 1.8, p < 0.001), right-sided intra-atrial (21.9 ± 8.2 vs. 10.4 ± 3.5, p < 0.001) and interatrial [40 (25-64) ms vs. 23 (14-27) ms p < 0.001] electromechanical interval (EMI) compared with the control group. Pd was significantly greater in the FMS group compared with the control group [46 (29-62) ms vs. 32 (25-37) ms, p < 0.001]. In the FMS group, there was no significant relationship of the echocardiographic parameters of ACT, Pmax and Pd with age, E/A ratio and deceleration time (DT); while all these five parameters were significantly correlated with left atrial dimension, isovolumetric relaxation time (IVRT), fibromyalgia impact questionnaire (FIQ) and visual analogue scale (VAS). There was a strong correlation between FIQ and VAS and echocardiographic parameters of ACT, Pmax and Pd. Conclusions: Impaired diastolic functions, an increase in Pd, and prolongation of ACT were observed in FMS. Current disorders are thought to be associated with an increased risk of AF in FMS. The risk of developing AF increases with the severity of FMS and clinical progression.(AU)

Medication Adherence Using Electronic Monitoring in Severe Psychiatric Illness: 4 and 24 Weeks after Discharge

OBJECTIVE: The purpose of this study was to examine post-hospitalization outpatient drug adherence in patients with severe psychiatric illness, including bipolar disorder and schizophrenia, and to investigate factors associated with drug adherence. METHODS: Eighty-one patients diagnosed with schizophrenia or bipolar disorder who were hospitalized due to aggravation of psychiatric symptoms were monitored. At hospitalization, we conducted clinical assessments such as the Clinical Global Impression-Severity, Drug Attitude Inventory, Contour Drawing Rating Scale, Multidimensional Scale of Perceived Social Support scale, and patients' demographic factors. We measured drug adherence using the Medication Event Monitoring System (MEMS), pill count, and patients' self-report upon out-patients visits, 4 and 24 weeks after discharge. RESULTS: The mean values of the various measures of adherence were as follows: MEMS (4 weeks) 84.8%, pill count (4 weeks) 94.6%, self-report (4 weeks) 92.6%, MEMS (24 weeks) 81.6%, pill count (24 weeks) 90.6%, and self-report (24 weeks) 93.6%. The adherence agreement between MEMS, pill count, and self-report was moderate (4 weeks intra-class correlation [ICC]=0.54, 24 weeks ICC=0.52). Non-adherence (MEMS ≤0.08) was observed in 26.4% of the patients at 4 weeks and 37.7% at 24 weeks. There was a negative correlation between drug adherence assessed 4 weeks after discharge and Contour Drawing Rating Scale difference score (r=−0.282, p<0.05). A positive correlation was found between drug adherence assessed 24 weeks after discharge and Drug Attitude Inventory (r=0.383, p<0.01). CONCLUSION: Patients' attitude towards their medication and their degree of physical dissatisfaction influenced post-hospitalization drug adherence in severe psychiatric patients.

Design and Implementation of Heart Sound Detection Device Based on MEMS MIC / 中国医疗器械杂志

The paper describes how to develop a digital heart sound signal detection device based on high gain MEMS MIC that can accurately collect and store human heart sounds. According to the method of collecting heart sound signal by traditional stethoscope, the system improves the traditional stethoscope, and a composite probe equipped with a MEMS microphone sensor is designed. The MEMS microphone sensor converts the sound pressure signal into a voltage signal, and then amplifies, converts with Sigma Delta, extracts and filters the collected signal. After the heart sound signal is uploaded to the PC, the Empirical Mode Decomposition (EMD) is carried out to reconstruct the signal, and then the Independent Component Analysis (ICA) method is used for blind source separation and finally the heart rate is calculated by autocorrelation analysis. At the end of the paper, a preliminary comparative analysis of the performance of the system was carried out, and the accuracy of the heart sound signal was verified.

A Capacitive Venous Transfusion Alertor Based on NB-IoT / 中国医疗器械杂志

This capacitive venous transfusion alertor is based on rise time of RC circuit and input capture function of timer in the microcontroller. The measure element of alertor is integrated with circuit board, it has the advantages of simple structure and low cost. Combined with narrow band intent of things(NB-IoT) technology to upload data, it can reduce the workload of medical personnel and caregivers, avoid unnecessary trouble and danger.

Review on Fabrication and Manipulation of Scaffold and Ciliary Microrobots / 한양의대학술지

Various microrobots are being studied for potential biomedical applications including targeted cell transportation, precise drug delivery, opening blocked blood vessels, micro-surgery, sensing, and scaffolding. Precise magnetic field control system is a coil system for wireless control of those microrobots for personalized and minimally invasive treatments. The microrobots for possible biomedical applications are fabricated by micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS) technologies. In this review, fabrication technologies for scaffold and ciliary microrobots will be introduced and their control methods will be discussed. Various materials are being used for the fabrication of the microrobot such as SU-8, IP-Dip, IP-L, silicon, etc. The scaffold and ciliary microrobots are fabricated by SU-8, IP-Dip, and IP-L because these materials showed the maximum performance for three-dimensional (3D) microrobots using a 3D laser lithography system. All or part of the structures are coated with nickel and titanium layers after fabrication of the structures for magnetic control and biocompatibility, respectively, of the microrobots.

Review on Fabrication and Manipulation of Scaffold and Ciliary Microrobots / 한양의대학술지

Various microrobots are being studied for potential biomedical applications including targeted cell transportation, precise drug delivery, opening blocked blood vessels, micro-surgery, sensing, and scaffolding. Precise magnetic field control system is a coil system for wireless control of those microrobots for personalized and minimally invasive treatments. The microrobots for possible biomedical applications are fabricated by micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS) technologies. In this review, fabrication technologies for scaffold and ciliary microrobots will be introduced and their control methods will be discussed. Various materials are being used for the fabrication of the microrobot such as SU-8, IP-Dip, IP-L, silicon, etc. The scaffold and ciliary microrobots are fabricated by SU-8, IP-Dip, and IP-L because these materials showed the maximum performance for three-dimensional (3D) microrobots using a 3D laser lithography system. All or part of the structures are coated with nickel and titanium layers after fabrication of the structures for magnetic control and biocompatibility, respectively, of the microrobots.

Variables Influencing Drug Adherence in Patients with Alzheimer's Disease

OBJECTIVES: Many patients with Alzheimer's disease have difficulty in taking their medicine by themselves and their poor drug adherence possibly results in aggravating various symptoms. The aim of this study was to assess the variables influencing drug adherence of Alzheimer's disease patients. METHODS: In a four-week period, 33 outpatients over 65 years old diagnosed with Alzheimer's disease were monitored. Drug adherences were assessed by the Medication Event Monitoring System (MEMS), the pill count, the clinician rating scale, and self-report. Agreements among adherence measures and the relationships between MEMS adherence and other clinical factors were assessed. RESULTS: The adherence rates for the MEMS, the pill count, the clinician rating scale and, self-report were 51.5%, 82.8%, 82.8%, and 87.9%. The Kappa coefficients were 0.382 (pill count vs. MEMS, clinician rating scale vs. MEMS) and 0.256 (self-report vs. MEMS). Males showed better adherence than females but the other clinical variables did not show significant differences between adherence group and non-adherence group. CONCLUSION: These findings suggest that clinicians should be concerned when assessing drug adherence in patients with Alzheimer's disease only by subjective reporting and pill counting since these methods may make patient's adherence underestimate. Clinicians should also take in mind that caregivers play an important role in improving adherence.

Recent Progress in Lab-on-a-Chip Technology and Its Potential Application to Clinical Diagnoses / 대한배뇨장애요실금학회지

We present the construction of the lab-on-a-chip (LOC) system, a state-of-the-art technology that uses polymer materials (i.e., poly[dimethylsiloxane]) for the miniaturization of conventional laboratory apparatuses, and show the potential use of these microfluidic devices in clinical applications. In particular, we introduce the independent unit components of the LOC system and demonstrate how each component can be functionally integrated into one monolithic system for the realization of a LOC system. In specific, we demonstrate microscale polymerase chain reaction with the use of a single heater, a microscale sample injection device with a disposable plastic syringe and a strategy for device assembly under environmentally mild conditions assisted by surface modification techniques. In this way, we endeavor to construct a totally integrated, disposable microfluidic system operated by a single mode, the pressure, which can be applied on-site with enhanced device portability and disposability and with simple and rapid operation for medical and clinical diagnoses, potentially extending its application to urodynamic studies in molecular level.