Development Of Microelectromechanical Systems Research Articles

Analysis of MEMS sensor application and prospects

The development trends in modern science and technology are miniaturization, integration, and intelligence. Microsensors have developed rapidly with the development of micro-electromechanical systems (MEMS) and micromachining technology. In this paper, the concepts and types of MEMS sensors are summarized by literature and case analyses, and their research statuses and application fields are briefly introduced. The development trends of MEMS sensors are discussed. This paper finds that combining sensors with intelligent products can achieve another application climax of MEMS sensors.

Acoustofluidics - changing paradigm in tissue engineering, therapeutics development, and biosensing.

For more than 70 years, acoustic waves have been used to screen, diagnose, and treat patients in hundreds of medical devices. The biocompatible nature of acoustic waves, their non-invasive and contactless operation, and their compatibility with wide visualization techniques are just a few of the many features that lead to the clinical success of sound-powered devices. The development of microelectromechanical systems and fabrication technologies in the past two decades reignited the spark of acoustics in the discovery of unique microscale bio applications. Acoustofluidics, the combination of acoustic waves and fluid mechanics in the nano and micro-realm, allowed researchers to access high-resolution and controllable manipulation and sensing tools for particle separation, isolation and enrichment, patterning of cells and bioparticles, fluid handling, and point of care biosensing strategies. This versatility and attractiveness of acoustofluidics have led to the rapid expansion of platforms and methods, making it also challenging for users to select the best acoustic technology. Depending on the setup, acoustic devices can offer a diverse level of biocompatibility, throughput, versatility, and sensitivity, where each of these considerations can become the design priority based on the application. In this paper, we aim to overview the recent advancements of acoustofluidics in the multifaceted fields of regenerative medicine, therapeutic development, and diagnosis and provide researchers with the necessary information needed to choose the best-suited acoustic technology for their application. Moreover, the effect of acoustofluidic systems on phenotypic behavior of living organisms are investigated. The review starts with a brief explanation of acoustofluidic principles, the different working mechanisms, and the advantages or challenges of commonly used platforms based on the state-of-the-art design features of acoustofluidic technologies. Finally, we present an outlook of potential trends, the areas to be explored, and the challenges that need to be overcome in developing acoustofluidic platforms that can echo the clinical success of conventional ultrasound-based devices.

ZnO Nanoparticle-Based MEMS Sensors for H2S Detection

The development of microelectromechanical system (MEMS)-based sensors with ZnO nanoparticles as sensitive materials for detecting a low concentration of H2S has recently attracted extensive attention because of their small size and easy integration. In this study, undecorated ZnO nanoparticles were synthesized by a facile coprecipitation method with the regulation of ammonia water. The phase structure, nanostructure, specific area, surface basicity, and oxygen species of the synthesized ZnO nanoparticles were systematically investigated. Then, preferred ZnO-1 nanoparticles were deposited on the MEMS microhotplate chips as a sensitive material, and the corresponding gas-sensing performances were characterized for various gases at an optimal operating temperature of 220 °C. The MEMS-based sensors with ZnO-1 showed good sensitivity to 1 ppm H2S at 220 °C with response/recovery times of 72 and 29 s, respectively. Furthermore, the sensor presented a wide linear range from 50 ppb to 15 ppm, good repeatability, and high selectivity. Such enhanced sensing performance to H2S was mainly attributed to the large surface area and the high surface basicity of prepared ZnO-1 nanoparticles. Moreover, a plausible reason for the enhanced sensing performance was also proposed.

Multi-Inertial Sensor-Based Arm 3D Motion Tracking Using Elman Neural Network

Recent years have witnessed the rapid development of microelectromechanical systems, and human motion tracking technology based on IMU (inertial measurement unit) has attracted much attention. However, the magnetic field varies with time and position, which makes it necessary to calibrate sensors before tracking. To address the poor adaptability of IMU to the environments and improve the accuracy of estimated traces, this paper presents an ENN-based (Elman neural network) method to track human arm motions, which consists of two steps. First, the data derived from IMUs are preprocessed for the rough Euler angles; then, an ENN is trained to estimate motions. We explore the initially estimated position to calibrate the acceleration measurements as the input of the ENN. Real-world experiments of arm motion tracking are carried out with the ground truth from an optical motion tracking system. The experimental results show that the mean tracking errors are around 35 mm, with a strong ability to eliminate the effect of extreme measurement and environment noises, avoiding calibrating the magnetometer. The implementation of the well-trained model to independent motions indicates that the robustness of the proposed method is excellent, and the errors reduce by 37.2% on the x -axis and perform similarly on the z -axis compared with 4 traditional methods. This method quite suits those situations where trajectory tracking of the standardized motions is required, such as the medical habilitation.

An overview of MEMS S&A device and its application in the micro-detonated system

The integration of fuzes and initiators has been promoted by the development requirements of the miniaturized and intelligent ammunition, and the micro-detonated system integrated with S&A device is the key development direction. Initiators are considered the first component of the weapon system, and the safety and reliability of the initiators directly affect the safety and reliability of the weapon system. With the development of micro-electromechanical system (MEMS) initiators and the integration of fuze, in order to further improve the safety of the weapon system in the miniaturized and intelligent ammunition system, it is necessary to integrate the MEMS S&A device with the initiators, which is an important technical feature, to form a MEMS initiator with functional integration, high safety and reliability. MEMS S&A device is the key technology of the MEMS initiators’ devices with safety-isolation function. This paper summarizes the development of MEMS S&A devices in micro-fuzes and the micro-detonated systems in recent years. Combined with comparative analysis, it analyzes and summarizes the driving principles, application platforms, process technologies, structural material characteristics and other aspects, and proposes a suitable structure for the MEMS initiators integrated with S&A devices, which provides a reference for the research on the design of MEMS initiators with safety-isolation function.

Organic-Inorganic Hybrid Polysiloxane Brushes with Improved Lubrication and Load-Bearing Capacity.

With the development of microelectromechanical systems (MEMS), ultrathin dry lubrication coatings have received significant attention. In this study, a nanoscale organic-inorganic hybrid lubricative coating (OHL) with a low friction coefficient and wear resistance was developed by grafting polysiloxane brushes on an inorganic silica sol layer. Friction evaluations, including the friction coefficient, load-bearing capacity, abrasion, and durability, were conducted. Compared with the surface of polysiloxane brushes without a silica sol layer, the introduction of a silica sol interlayer can effectively improve the mechanical stability of polysiloxane brushes; namely, the friction coefficient under high load pressure was able to remain low for a long time. In addition, the lubrication performance can also further improve by modifying the upper friction pair surface with the OHL. More importantly, the OHL has an excellent stability and general applicability. The OHL coating can be applied to various solid surfaces that provide a similar lubrication performance, which may provide a new vision for reducing the friction coefficient and enhancing the wear resistance, especially under dry friction conditions.

Cell-Based Microfluidic Device Utilizing Cell Sheet Technology.

The development of microelectromechanical systems has resulted in the rapid development of polydimethylpolysiloxane (PDMS) microfluidic devices for drug screening models. Various cell functions, such as the response of endothelial cells to fluids, have been elucidated using microfluidic devices. Additionally, organ-on-a-chip systems that include organs that are important for biological circulation, such as the heart, liver, pancreas, kidneys, and brain, have been developed. These organs realize the biological circulation system in a manner that cannot be reproduced by artificial organs; however, the flow channels between the organs are often artificially created by PDMS. In this study, we developed a microfluidic device consisting only of cells, by combining cell sheet technology with microtitanium wires. Microwires were placed between stacked fibroblast cell sheets, and the cell sheets adhered to each other, after which the microwires were removed leaving a luminal structure with a size approximately equal to the arteriolar size. The lumen structure was constructed using wires with diameters of 50, 100, 150, and 200 μm, which were approximations of the arteriole diameters. Furthermore, using a perfusion device, we successfully perfused the luminal structure created inside the cell sheets. The results revealed that a culture solution can be supplied to a cell sheet with a very high cell density. The biofabrication technology proposed in this study can contribute to the development of organ-on-a-chip systems.

Detection and identification of gas components based on nano sensor array

<sec>In recent years, quite a few production safety accidents caused by hazardous gas leakage have occurred in the petrochemical industry, causing great potential safety hazards and huge economic losses. Therefore, it is necessary to develop gas sensors with high sensitivity and accurate identification. Semiconductor gas sensor, which has the advantages of high sensitivity, fast response and high integration, is one of the most popular types in the sensing field. However, the semiconductor gas sensor has low specific recognition to reducing gases (such as H<sub>2</sub>S, CO, H<sub>2</sub>, etc.), and it is difficult to accurately achieve mixed-gas identification with a single sensor. With the development of micro-electromechanical systems (MEMS), the size of semiconductor sensor can be reduced to millimeters with high integration. In order to solve the cross-sensitivity problem, the concept of sensor array has been proposed and widely studied. Through the principal component analysis, the data having the most characteristic information can be selected from among the acquired data while preserving the original data information as much as possible, and they are projected onto the new orthogonal vector by linear transformation. This method can maximize data dispersion and minimize information loss after dimensionality reduction. Therefore, it is an effective way to identify the gas species by combining sensor array.</sec><sec>In this work, we synthesize four types of tungsten trioxide sensing materials with different morphologies or compositions by the hydrothermal method. The sensor array is fabricated by MEMS-based nano sensors. The gas sensitivities to the four single gases (H<sub>2</sub>S, CO, H<sub>2</sub>, NH<sub>3</sub>) and their mixed gas are measured by sensor array, which can acquire four groups of data at the same time. Compared with single sensor, the sensor array has different responses to pure gas and mixed gas, which is the basis for gas identification. Furthermore, we use principal component analysis method to process the response of sensor array. The results show that different gases will occupy different areas in the diagram for pure gas, and show certain directionality according to different concentration distributions. By determining the position of the detected gas, the composition and concentration of the measured gas can be inferred. For mixed gas, the distributions of single gases show the same tendency. And the points of mixed gas always occupy the area between the fans formed by the two gas components, and each region keeps independent. Therefore, this method can also identify the compositions and the concentrations of gas species contained in mixed gas. These results prove that nano sensor array can provide direction and guidance for semiconductor sensor to identify the gas species and concentration.</sec>

Readout Circuits for Capacitive Sensors.

The development of microelectromechanical system (MEMS) processes enables the integration of capacitive sensors into silicon integrated circuits. These sensors have been gaining considerable attention as a solution for mobile and internet of things (IoT) devices because of their low power consumption. In this study, we introduce the operating principle of representative capacitive sensors and discuss the major technical challenges, solutions, and future tasks for a capacitive readout system. The signal-to-noise ratio (SNR) is the most important performance parameter for a sensor system that measures changes in physical quantities; in addition, power consumption is another important factor because of the characteristics of mobile and IoT devices. Signal power degradation and noise, which degrade the SNR in the sensor readout system, are analyzed; circuit design approaches for degradation prevention are discussed. Further, we discuss the previous efforts and existing studies that focus on low power consumption. We present detailed circuit techniques and illustrate their effectiveness in suppressing signal power degradation and achieving lower noise levels via application to a design example of an actual MEMS microphone readout system.

Low‐frequency nanocomposite piezoelectric energy harvester with embedded zinc oxide nanowires

AbstractSweeping developments in microelectromechanical systems and low power electronics have pushed the need for piezoelectric energy harvesters (PEHs). Increasing environmental and biocompatibility issues have drawn interest in lead‐free piezoelectric materials. In this paper, cantilever‐type PEHs at centimeter scale have been proposed to harvest the energies of low‐frequency vibrations caused by a human's movements. The proposed PEHs are made of a passive PDMS substrate sandwiched between two active nanocomposite layers with embedded piezoelectric zinc oxide (ZnO) nanowires. Moreover, two different morphologies including PEHs with constant and tapered thicknesses have been considered. The material properties of such piezoelectric nanocomposites are calculated by an electromechanical model. Afterward, these novel PEHs have been developed in COMSOL Multiphysics and their static and dynamic performances have been investigated. The static study shows that tapered PEHs endures lower stresses. However, the dynamic study discloses that the rectangular design outperforms the tapered one in electrical power and resonance frequency. It is found that the rectangular design can produce 4.1623 μW at the resonant frequency of 25.8 Hz.

A novel cooperative compensation method to compensate for return stroke of stick-slip piezoelectric actuators

With the development of micro-electromechanical systems, high precision actuators with high resolution, fast speed, large load capacity are increasingly required. Thanks to the characteristics of flexible structure, fast step speed, low energy consumption, high resolution and unlimited stroke range, stick-slip actuators have been drawing worldwide attention. Traditionally, stick-slip actuators are driven by sawtooth waveform signals with a slow increase and a fast decrease. Therefore, there is an unavoidable return stroke when fast decrease of the driving signal appears, which reduces driving speed and efficiency. In this paper, a novel cooperative compensation method (CCM) to compensate for return stroke of stick-slip actuators is proposed. It uses two signals of specific initial time gap (ITG) to reduce the return stroke to improve speed. A modified two-layer stick-slip piezoelectric actuator based on a triangular compliant driving mechanism is built. Experimental results show that the CCM can effectively increase step size of the actuator, especially driven under low frequencies. When signal is at 10 Hz, the step size of the actuator With CCM is over 29 times of that with traditional single-PSA-driving method (TSM). The maximum step size with CCM is 4.448 µm at 250 Hz, which is more than 40% of TSM.

Кинематический расчет элементов микрозеркал микроэлектромеханических систем (MEMS)

Currently, the development and application of micro machines is an important direction in the development of microelectromechanical systems (MEMS) technologies. In these devices, electromechanical energy conversion occurs, as a result of which forces arise that carry out mechanical work within the dimensions of the microcircuit case. The paper considers the kinematic calculation of the design of a micromirror with a reflective layer of high optical quality of the surface for deflecting the reflected laser beam. By changing the angle of inclination of the micromirror, the laser beam enters the various input channels of the optical sensor. In this case, a control signal is generated for the further operation of the microcircuit. Thus, the micromirror performs the function of a switch of input optical channels, connecting in various combinations certain input or output elements of the microcircuit for further processing. The article presents the calculation of the kinematic parameters of the mechanical structure of the micro mirror. Practical recommendations are given for choosing the optimal range of variation of the micro mirror tilt angles in order to increase the strength of its structure, as well as to reduce the power of the mechanical drive of the micro machine required to change the micro mirror tilt angles

Positioning of Wireless Sensor Network under Emergency Communication Environment

With the development of microelectromechanical system (MEMS), embedded system, and wireless communication, it is now feasible to implement and deploy wireless sensor network (WSN) in emergency communication environment. However, the positioning accuracy of WSN nodes needs to be further improved. To solve the problem, this paper improves the initial value calculation method of multi-hop positioning algorithms, which are suitable for emergency communication environment, and puts forward a WSN node positioning algorithm that narrows the initial values of Kalman filter. By narrowing the initial value range of Kalman filter, the specially deployed sensors could accurately derive its position from the known positions of anchor nodes. To prevent error accumulation in the network, distributed computing was performed to solve the global nonlinear optimization problem, and calculate the position of the nodes. Simulation results show that the proposed algorithm can improve the WSN positioning accuracy under emergency communication environment, while greatly saving computing and communication costs. The research further improves the practicability and efficiency of multi-hop positioning algorithms in emergency communication environment.

Gait recognition via random forests based on wearable inertial measurement unit

In recent years, gait detection has been widely used in medical rehabilitation, smart phone, criminal investigation, navigation and positioning and other fields. With the rapid development of micro-electro mechanical systems, inertial measurement unit (IMU) has been widely used in the field of gait recognition with many advantages, such as low cost, small size, and light weight. Therefore, this paper proposes a gait recognition algorithm based on IMU, which is named as FPRF-GR. Firstly, a fusion feature engineering operator is designed to eliminate redundant and defective features, which is mainly based on Fast Fourier Transform and principal component analysis. Then, in the design of classifier, in order to meet the requirements of gait recognition model for accuracy, generalization ability, speed, and noise resistance, this paper compares random forest (RF) and several commonly used classification algorithms, and finds that the model constructed by RF can meet the requirements. FPRF-GR builds the model based on RF, and uses the tenfold cross validation method to evaluate the model. Finally, this paper proposes an optimization scheme for the two parameters of decision tree number and sample number in RF. The results show that FPRF-GR can identify five gaits (walk, stationary, run, and up and down stairs) with the average accuracy of 98.2%.

OPTIMIZATION OF THE PRESURE NEGATIVE WAVE METHOD UNDER PIPELINES STATE DIAGNOSTICS

Background With the development of microelectromechanical systems, small-sized devices for diagnosing the state of pipelines appear, and based on them, wireless networks for monitoring the occurrence of leaks in main pipelines. The main disadvantage of optical methods is their relatively low speed, because for their normal functioning, a certain amount of gas must exit into the outer space. This drawback is a characteristic of almost all direct methods for detecting a gas leak, since the interaction of a probing signal (optical, acoustic or other type) with the gas cloud formed is necessary. In contrast to such direct methods, there are indirect methods in which it is not the in-tube mass itself that is detected, but some indicator of this mass inside the pipeline. In the method of registering a negative pressure wave inside the pipeline, such an indicator is the pressure in the pipe. The article is devoted to optimizing the diagnosis of pipe lines using the negative pressure wave method. Aims and Objectives Development of the optimization task for the pressure negative wave method to determine the place of leakage from the pipeline. Results The solution to the task of determining the place of leakage from the pipeline by the method of unconditional variational optimization showed that in main pipeline sections, where the intersensory interval is higher, the pressure in the pipe should be reduced so that the maximum value of the average detectable distance to the leakage in sections of the pipeline can be reached. The condition is calculated under which the pressure in the corresponding section of the pipeline can have a minimum value.

A two-port electrothermal model for suspended MEMS device structures with multiple inputs

Abstract. Advances in micromachining have led to the development of microelectromechanical systems (MEMS) devices with suspended structures used in a variety of sensors. Of note for this work are sensor types where two elements exist on the suspended membrane, including examples like air flow and differential pressure detectors, gas detection, and differential scanning calorimetry sensors. Intuitively one would argue that some thermal loss exists between the two elements. However, surprisingly little is documented about this electrothermal interaction. The work presented here addresses this shortcoming by defining a new parameter set, a matrix of thermal coupling coefficients. They are used within our novel two-port electrothermal model based on the heat flow equation adapted as a linear system of equations. However, the model is only effective with knowledge of these coefficients. We introduce an approach to extract the coefficients using finite-element method (FEM)-based multiphysics simulation tools and revisit and extend our previous method of non-ideal power coupling, this time to extract the coefficient matrix from measured data. Both specialist simulation tools and device manufacturing are very expensive. However, they are the only choices in the absence of an analytic model. A major contribution of this work is the derivation of a model to predict the coefficients by analytic means from the device dimensions and material properties. The research contribution and paper culminate in a comparison of analytic, simulated, and experimentally extracted values of two different devices to verify and demonstrate the effectiveness of the proposed models. The values compare well and show that the best results achieved are approximately 90 % and 70 % thermal linkage respectively for vacuum and atmospheric pressure conditions.

A Novel Method of Adaptive Kalman Filter for Heading Estimation Based on an Autoregressive Model

With the popularity of smartphones and the development of microelectromechanical system (MEMS), the pedestrian dead reckoning (PDR) algorithm based on the built-in sensors of a smartphone has attracted much research. Heading estimation is the key to obtaining reliable position information. Hence, an adaptive Kalman filter (AKF) based on an autoregressive model (AR) is proposed to improve the accuracy of heading for pedestrian dead reckoning in a complex indoor environment. Our approach uses an autoregressive model to build a Kalman filter (KF), and the heading is calculated by the gyroscope, obtained by the magnetometer, and stored by previous estimates, then are fused to determine the measurement heading. An AKF based on the innovation sequence is used to adaptively adjust the state variance matrix to enhance the accuracy of the heading estimation. In order to suppress the drift of the gyroscope, the heading calculated by the AKF is used to correct the heading calculated by the outputs of the gyroscope if a quasi-static magnetic field is detected. Data were collected using two smartphones. These experiments showed that the average error of two-dimensional (2D) position estimation obtained by the proposed algorithm is reduced by 40.00% and 66.39%, and the root mean square (RMS) is improved by 43.87% and 66.79%, respectively, for these two smartphones.

Magnetohydrodynamic velocity profile measurement for microelectromechanical systems micro-robot design

The development of microelectromechanical systems based on magnetohydrodynamic for micro-robot applications requires precise control of the micro-flow behavior. The micro-flow channel design and its performance under the influence of the Lorentz force is a critical challenge, the mathematical model of each magnetohydrodynamic device design must be experimentally validated before to be employed in the fabrication of microelectromechanical systems. For this purpose, the present article proposes the enhancement of a particle image velocimetry measurement process in a customized machine vision system. The particle image velocimetry measurements are performed for the micro-flow velocity profile mathematical model validation of a magnetohydrodynamic stirrer prototype. Data mining and filtering have been applied to a raw measurement database from the customized machine vision system designed to evaluate the magnetohydrodynamic stirrer prototype. Outlier’s elimination and smoothing have been applied to raw data to approximate the particle image velocimetry measurements output to the velocity profile mathematical model to increase the accuracy of a customized machine vision system for two-dimensional velocity profile measurements. The accurate measurement of the two-dimensional velocity profile is fundamental owing to the requirement of future enhancement of the customized machine vision system to construct the three-dimensional velocity profile of the magnetohydrodynamic stirrer prototype. The presented methodology can be used for measurement and validation in the design of microelectromechanical systems micro-robot design and any other devices that require micro-flow manipulation for tasks such as stirring, pumping, mixing, networking, propelling, and even cooling.

A review of principles of MEMS pressure sensing with its aerospace applications

PurposePressure, being one of the key variables investigated in scientific and engineering research, requires critical and accurate measurement techniques. With the advancements in materials and machining technologies, there is a large leap in the measurement techniques including the development of micro electromechanical systems (MEMS) sensors. These sensors are one to two orders smaller in magnitude than traditional sensors and combine electrical and mechanical components that are fabricated using integrated circuit batch-processing technologies. MEMS are finding enormous applications in many industrial fields ranging from medical to automotive, communication to electronics, chemical to aviation and many more with a potential market of billions of dollars. MEMS pressure sensors are now widely used devices owing to their intrinsic properties of small size, light weight, low cost, ease of batch fabrication and integration with an electronic circuit. This paper aims to identify and analyze the common pressure sensing techniques and discuss their uses and advantages. As per our understanding, usage of MEMS pressure sensors in the aerospace industry is quite limited due to cost constraints and indirect measurement approaches owing to the inability to locate sensors in harsh environments. The purpose of this study is to summarize the published literature for application of MEMS pressure sensors in the said field. Five broad application areas have been investigated including: propulsion/turbomachinery applications, turbulent flow diagnosis, experimentalaerodynamics, micro-flow control and unmanned aerial vehicle (UAV)/micro aerial vehicle (MAV) applications.Design/methodology/approachThe first part of the paper deals with an introduction to MEMS pressure sensors and mathematical relations for its fabrication. The second part covers pressure sensing principles followed by the application of MEMS pressure sensors in five major fields of aerospace industry.FindingsIn this paper, various pressure sensing principles in MEMS and applications of MEMS technology in the aerospace industry have been reviewed. Five application fields have been investigated including: Propulsion/Turbomachinery applications, turbulent flow diagnosis, experimental aerodynamics, micro-flow control and UAV/MAV applications. Applications of MEMS sensors in the aerospace industry are quite limited due to requirements of very high accuracy, high reliability and harsh environment survivability. However, the potential for growth of this technology is foreseen due to inherent features of MEMS sensors’ being light weight, low cost, ease of batch fabrication and capability of integration with electric circuits. All these advantages are very relevant to the aerospace industry. This work is an endeavor to present a comprehensive review of such MEMS pressure sensors, which are used in the aerospace industry and have been reported in recent literature.Originality/valueAs per the author’s understanding, usage of MEMS pressure sensors in the aerospace industry is quite limited due to cost constraints and indirect measurement approaches owing to the inability to locate sensors in harsh environments. Present work is a prime effort in summarizing the published literature for application of MEMS pressure sensors in the said field. Five broad application areas have been investigated including: propulsion/turbomachinery applications, turbulent flow diagnosis, experimental aerodynamics, micro-flow control and UAV/MAV applications.

Gold-implanted plasmonic quartz plate as a launch pad for laser-driven photoacoustic microfluidic pumps

Enabled initially by the development of microelectromechanical systems, current microfluidic pumps still require advanced microfabrication techniques to create a variety of fluid-driving mechanisms. Here we report a generation of micropumps that involve no moving parts and microstructures. This micropump is based on a principle of photoacoustic laser streaming and is simply made of an Au-implanted plasmonic quartz plate. Under a pulsed laser excitation, any point on the plate can generate a directional long-lasting ultrasound wave which drives the fluid via acoustic streaming. Manipulating and programming laser beams can easily create a single pump, a moving pump, and multiple pumps. The underlying pumping mechanism of photoacoustic streaming is verified by high-speed imaging of the fluid motion after a single laser pulse. As many light-absorbing materials have been identified for efficient photoacoustic generation, photoacoustic micropumps can have diversity in their implementation. These laser-driven fabrication-free micropumps open up a generation of pumping technology and opportunities for easy integration and versatile microfluidic applications.