The Internet of Things (IoT) aims to connect billions of smart objects to the Internet, which can bring a promising future to smart cities. These objects are expected to generate large amounts of data and send the data to the cloud for further processing, especially for knowledge discovery, in order that appropriate actions can be taken. However, in reality sensing all possible data items captured by a smart object and then sending the complete captured data to the cloud is less useful. Further, such an approach would also lead to resource wastage (e.g., network, storage, etc.). The Fog (Edge) computing paradigm has been proposed to counterpart the weakness by pushing processes of knowledge discovery using data analytics to the edges. However, edge devices have limited computational capabilities. Due to inherited strengths and weaknesses, neither Cloud computing nor Fog computing paradigm addresses these challenges alone. Therefore, both paradigms need to work together in order to build a sustainable IoT infrastructure for smart cities. In this article, we review existing approaches that have been proposed to tackle the challenges in the Fog computing domain. Specifically, we describe several inspiring use case scenarios of Fog computing, identify ten key characteristics and common features of Fog computing, and compare more than 30 existing research efforts in this domain. Based on our review, we further identify several major functionalities that ideal Fog computing platforms should support and a number of open challenges toward implementing them, to shed light on future research directions on realizing Fog computing for building sustainable smart cities.

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Fog Computing for Sustainable Smart Cities: A Survey

In recent years, shape memory alloy (SMA) thin films have attracted significant attention from the scientific community and industry for their potential applications in the field of smart sensors and actuators, micro- and nano-electromechanical systems, aerospace, automobile, and biomedical. The present article focuses on the recent developments in the field of SMA thin films and their heterostructures with other materials for potential microelectromechanical systems (MEMS) applications. Various microdevices such as microgrippers, micropumps, microvalves, and cantilevers fabricated from binary and ternary SMA films have been discussed in detail. SMA thin films combined with various nitrides, oxides, and ferroelectric layers offer excellent surface modification and vibration damping at microscale for their use in harsh environments. The article encompasses the new paradigms in the field of SMA thin films that have been essentially developed by the authors and co-workers during the past 6 years.

Shape memory alloy thin films and heterostructures for MEMS applications: A review

Janus particles can self-assemble around microfabricated gears in reproducible configurations with a high degree of spatial and orientational order. The final configuration maximizes the torque applied on the rotor leading to a unidirectional and steady rotating motion. The interplay between geometry and dynamical behavior leads to the self-assembly of Janus micromotors starting from randomly distributed particles.

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Self-Assembly of Micromachining Systems Powered by Janus Micromotors

The design and control of a novel piezoelectric actuated compliant microgripper is studied in this paper to achieve fast, precise, and robust micro grasping operations. First, the microgripper mechanism was designed to get a large jaw motion stroke. A three-stage flexure-based amplification composed of the homothetic bridge and leverage mechanisms was developed and the key structure parameters were optimized. The microgripper was manufactured using the wire electro discharge machining technique. Finite element analysis and experimental tests were carried out to examine the performance of the microgripper mechanism. The results show that the developed microgripper has a large amplification factor of 22.6. Dynamic modeling was conducted using experimental system identification, and the displacement and force transfer functions were obtained. The position/force switching control strategy was utilized to realize both precision position tracking and force regulation. The controller composed of an incremental proportional-integral-derivative control and a discrete sliding mode control with exponential reaching law was designed based on the dynamic models. Experiments were performed to investigate the control performance during micro grasping process, and the results show that the developed compliant microgripper exhibits good performance, and fast and robust grasping operations can be realized using the developed microgripper and controller.

Design and Control of a Compliant Microgripper With a Large Amplification Ratio for High-Speed Micro Manipulation

Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes

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In recent years, microelectromechanical systems (MEMS) have been widely applied in diverse science and en- gineering domains. MEMS-based microgrippers provide advantages in terms of compact size and low cost, and hence play an important role in microassembly and micromanipulation fields for manipulating micromechanical elements, bio- logical cells, etc. During the past two decades, microactuators based on different actuation principles such as shape- memory alloys, electrostatic, electrothermal, piezoelectric, pneumatic and electromagnetic approaches have been devised to drive MEMS microgrippers. Moreover, the integrated position and force sensors can deliver real-time feedback signals to protect both the microgripper and grasped object from damaging. In addition, a number of patents have been devoted to this area. This paper presents a state-of-the-art overview of recent development in the actuators (electrostatic, electrother- mal, micro-pneumatic, electromagnetic, shape memory alloy and other actuators) and sensors (optical method, piezoresis- tive force sensor, capacitive force sensor and other developments). By providing detailed comparisons among them, some guidelines of selection have been underlined for different application scenarios such as biomedical and biological applica- tions, micro-manufacturing and so on.

MEMS Microgripper Actuators and Sensors: The State-of-the-Art Survey

A micro-/nanopositioning system with both large motion range and compact size is highly desired in various precision engineering applications. In this paper, the design of a new compliant micropositioning stage with translational motion is proposed based on flexure mechanisms. The stage parameters are optimized by using the genetic algorithm (GA) to achieve a large natural frequency under the constraints on motion range (i.e., over 10 mm) and compact physical dimension along with a high safety factor for the material. Both analytical calculations and simulations based on finite element analysis are performed to validate the stage performances. A physical prototype system which employs a voice coil motor and a laser displacement sensor for actuation and sensing, respectively, is fabricated for experimental tests. Result confirms the long-stroke performance of the developed micropositioning system.

Design and optimization of a long-stroke compliant micropositioning stage driven by voice coil motor

This paper presents the design of a new monolithic two-axis electrostatically actuated MEMS microgripper with integrated capacitive position and force sensors working at the micro-scale level. Each of the two jaws of the microgripper possesses two degrees-of-freedom (DOF) and is capable of positioning in both x-and y-axes. Unlike existing works, where one gripper arm is actuated and other one is sensed, both arms of the proposed microgripper are actuated and sensed independently. A sensing scheme is constructed to provide the position and force signals in the noncontact and contact phases, respectively. By applying a 120V driving voltage, the jaw can provide 70 μm x-axis and 18 μm y-axis displacements with the force of 190 μN. By this design, the real-time position and grasping force information can be obtained in the dual sensing mode. Both analytical calculation and finite-element analysis (FEA) were performed to verify the performance of the proposed design. A scaled-up prototype is designed, fabricate...

https://journals.sagepub.com/doi/pdf/10.5772/59677

A Dual-Axis Electrostatically Driven MEMS Microgripper

This paper presents the design of a new monolithic two-axis electrostatically actuated MEMS microgripper with integrated capacitive position and force sensors working at the micro-scale level. Each of the two jaws of the microgripper possesses two degree-of-freedom (DOF) and is capable of positioning in both x- and y-axes. Moreover, different from existing works where one gripper arm is actuated and other one is sensed, both arms of the proposed microgripper are actuated and sensed independently. A sensing scheme is then constructed to provide the position and force signals in the noncontact phase and contact phase, respectively. By applying a 120-V driving voltage, the jaw can provide 70 μm X direction and 18 μm Y direction displacements with the force of 190 μN. By this design, the real-time position and grasping force information can be obtained in the dual sensing mode. The performance of the designed microgripper is verified by both analytical modeling and finite-element analysis.

Design of a monolithic dual-axis electrostatic actuation MEMS microgripper with capacitive position/force sensors

In this paper, the design of a new compliant two-axis PZT actuated gripper is proposed based on flexure mechanisms. Its uniqueness is that both of the two gripper jaws can achieve two degree-of-freedom (DOF) movement. A lever structure is designed to meet the requirement of larger displacement due to the stroke limitation of the actuator. The gripper parameters are optimized by using genetic algorithm (GA) to achieve the highest natural frequency under the constraints imposed by the compact size and displacement over 20 μm. Both analytical computation and FEA simulation are conducted to verify the static and dynamic performances of the proposed design. Moreover, a prototype gripper is fabricated and assembled with laser displacement sensor for experimental testing. The concept of the design is confirmed by the experimental results.

Yukun Jia

Papers

MEMS Microgripper Actuators and Sensors: The State-of-the-Art Survey

Design and optimization of a long-stroke compliant micropositioning stage driven by voice coil motor

A Dual-Axis Electrostatically Driven MEMS Microgripper

Design of a monolithic dual-axis electrostatic actuation MEMS microgripper with capacitive position/force sensors

Design and optimization of a dual-axis PZT actuation gripper