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CAD 3D models of the four fabricated and tested SOI MEMS grippers. Green is SOI, dark gray is substrate, and yellow is gold on SOI.
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... total, four MEMS grippers ( Figure 2) were designed and fabricated using a three mask silicon-oninsulator (SOI) process. The first mask patterns a 0.5µm e-beam evaporated gold layer, the second mask the 40µm silicon device layer, and the third mask the 550µm silicon substrate. ...
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Introduction
The monitoring of soil displacement during highway slope instability currently faces challenges such as poor stability, low accuracy, and high costs. In this study, a Micro-Electro-Mechanical System (MEMS) sensor is proposed for measuring internal soil displacement during slope movement. A method for converting MEMS-based acceleration...
Citations
... Following the novel implementation of the flexible, inclined arm to drive the inchworm motor's shuttle that was proposed by Penskiy et al. in 2012 [72], several more complex cooperative systems have used this optimized design and made it somewhat of a blueprint for more advanced inchworm motor implementations, such as a so-called 'inchworm-of-inchworms' motor topology with force amplification for a jumping microrobot by Greenspun et al. (Figure 13c) [77]; a MEMS airfoil actuator by Kilberg et al. [78]; another jumping microrobot by Schindler et al. [79]; an aerodynamic control of miniature rockets by Rauf et al. [80]; a microgripper with 15 mN of force and 1 mm of displacement by Schindler et al. [81]; and a remarkable, intricate realization of a cooperative electrostatic Figure 13. Examples of more elaborately cooperative systems for robotic applications that are based on inchworm motors: (a) a SEM image of a 2-DoF robotic leg, where each DoF (hip or knee) is driven by an inchworm motor (not fully shown). ...
... Following the novel implementation of the flexible, inclined arm to drive the inchworm motor's shuttle that was proposed by Penskiy et al. in 2012 [72], several more complex cooperative systems have used this optimized design and made it somewhat of a blueprint for more advanced inchworm motor implementations, such as a so-called 'inchworm-of-inchworms' motor topology with force amplification for a jumping microrobot by Greenspun et al. (Figure 13c) [77]; a MEMS airfoil actuator by Kilberg et al. [78]; another jumping microrobot by Schindler et al. [79]; an aerodynamic control of miniature rockets by Rauf et al. [80]; a microgripper with 15 mN of force and 1 mm of displacement by Schindler et al. [81]; and a remarkable, intricate realization of a cooperative electrostatic actuation in the form of a multichip terrestrial robot developed by Contreras [82]. In the latter, each leg of the six-legged robot had a 2-DoF planar silicon linkage, featuring rotary joints, that is operated by two separate inchworm motors. ...
... In addition, in standard surface micromachined motors, the thickness of the functional layer (poly-Si or thin c-Si device layer) is typically an order of magnitude smaller than HAR motors made out of such SOI wafers that have thicker device layers (e.g., >10 µm), this is a substantial drawback for applications that engages mesoscale loads, where the fabrication and force transfer become much more challenging. This conclusion is inferred from the prevailing trend witnessed in recent years towards HAR inchworm motors for applications involving a micro-macro transfer of force and displacement [77][78][79][80][81][82]98]. ...
Having benefited from technological developments, such as surface micromachining, high-aspect-ratio silicon micromachining and ongoing miniaturization in complementary metal–oxide–semiconductor (CMOS) technology, some electrostatic actuators became widely used in large-volume products today. However, due to reliability-related issues and inherent limitations, such as the pull-in instability and extremely small stroke and force, commercial electrostatic actuators are limited to basic implementations and the micro range, and thus cannot be employed in more intricate systems or scaled up to the macro range (mm stroke and N force). To overcome these limitations, cooperative electrostatic actuator systems have been researched by many groups in recent years. After defining the scope and three different levels of cooperation, this review provides an overview of examples of weak, medium and advanced cooperative architectures. As a specific class, hybrid cooperative architectures are presented, in which besides electrostatic actuation, another actuation principle is used. Inchworm motors—belonging to the advanced cooperative architectures—can provide, in principle, the link from the micro to the macro range. As a result of this outstanding potential, they are reviewed and analyzed here in more detail. However, despite promising research concepts and results, commercial applications are still missing. The acceptance of piezoelectric materials in some industrial CMOS facilities might now open the gate towards hybrid cooperative microactuators realized in high volumes in CMOS technology.
... Moreover, increasing the number of legs enables the system to be more robust due to the actuation failure [14]. The inchworm mechanism can gain control of the friction force by exploiting the squeeze film effect [15,16]. To create biologically-inspired flapping-wing microrobots like insects for exploration purposes, high-density actuation power [17] is required, which can be developed using piezoelectric materials. ...
Recent advances in precision manufacturing technology and a thorough understanding of the properties of piezoelectric materials have made it possible for researchers to develop innovative microrobotic systems, which draw more attention to the challenges of utilizing microrobots in areas that are inaccessible to ordinary robots. This review paper provides an overview of the recent advances in the application of piezoelectric materials in microrobots. The challenges of microrobots in the direction of autonomy are categorized into four sections: mechanisms, power, sensing, and control. In each section, innovative research ideas are presented to inspire researchers in their prospective microrobot designs according to specific applications. Novel mechanisms for the mobility of piezoelectric microrobots are reviewed and described. Additionally, as the piezoelectric micro-actuators require high-voltage electronics and onboard power supplies, we review ways of energy harvesting technology and lightweight micro-sensing mechanisms that contain piezoelectric devices to provide feedback, facilitating the use of control strategies to achieve the autonomous untethered movement of microrobots.
... These high voltage waveforms are then used to run the electrostatic inchworm motor on a MEMS microgripper suitable for microrobot and other applications. The gripper is able to produce 15mN (1.5 gram) gripping force [19]. Bypass capacitors were used on the PV supplies, but otherwise the only components in the demo were SCµM, the PV chip, and the MEMS gripper chip. ...
We have demonstrated an embedded microrobot control chip suitable for sub-cm robot platforms. The 2 × 3 × 0.3 mm 3 65 nm CMOS chip weighing 4 mg includes a 32 bit Cortex-M0 processor for control, standards-compatible 2.4 GHz RF communication, contact-free optical programming, and sub-cm accurate 3D localization using lighthouse beacons. The chip requires only three wires: power, ground, and a bondwire antenna. No other external components are necessary. With a two-chip solution, we have demonstrated solar-powered operation of 80V MEMS electrostatic inchworm motors suitable for microrobotics.
This paper presents a force sensor designed for a three-dimensional (3D) electrothermal microgripper. The novel force sensor structure incorporates a strain gauge attached to a compliant beam segment to accurately measure the forces exerted at the microgripper tip. Firstly, a comprehensive theoretical model for the force-strain-voltage relationship of the sensor is established. The model consists of two parts: force-strain with the static analysis of a flexible hinge resembling a composite beam, and strain-voltage with the physics of the sensing interface. In the force-strain part of the model, two equivalent transformations (the equivalent transformation of composite beam cross-Section to T-shaped beam cross-Section and the equivalent transformation of unconnected beam cross-Section to connected beam cross-Section) are used to establish the theoretical formulation between the gripping force and the sensor strain of the microgripper. The model is verified through the finite-element simulation and further validated through experimental testing of an in-house developed single finger with a comparison. According to the experimental results, the force sensor can detect the gripping force in the millinewton range. Finally, three force sensors are integrated into an in-house developed 3D electrothermal microgripper and the force detection with the proposed sensor design is further demonstrated with a series of micromanipulation experiments. The results reveal the dynamic variations in the micro-gripping force during 3D micro-manipulation due to the vibration of the mechanism, the relative sliding motion, and the gravity of the microspheres.
Maturation of robotics research and advances in the miniaturization of machines have contributed to the development of microbots and enabled new technological possibilities and applications. Microbots have a wide range of applications, including the navigation of confined spaces, environmental monitoring, micro-assembly and manipulation of small objects, and in vivo micro-surgeries and drug delivery. Actuators are among the most critical components that define the performance of robots. A comprehensive review of the actuation mechanisms that have been employed in mobile microbots is provided, including piezoelectric, magnetic, electrostatic, thermal, acoustic, biological, chemical, and optical actuation, with a focus on the most recent development and methodologies.
The geometrical constraints and dimensional tolerances lead to specific design issues of MEMS manipulators for biological applications. The target properties become even more important in the case of in vitro manipulation of cells. Several design solutions have been proposed in the literature, however, some issues related to the thermal heating of microgripper tips and to the electric voltage effects still remain unsolved. This paper reports the design for additive manufacturing (DFAM) of micro-electro mechanical systems (MEMS) microgrippers. The design limitations imposed by the micro-stereolithography fabrication process are considered. The design solution proposed in this study is based on compliant structures and external actuation; this layout provides the potential elimination of the main issues related to cells micro-manipulators represented by the excessive thermal heating and the voltage exposure of samples. The simulation through finite elements method (FEM) models of the structure in terms of force–displacement relation and stress distribution supports the design evolution proposed.
This work reports a three-dimensional polymer interdigitated pillar electrostatic actuator that can produce force densities 5–10× higher than those of biological muscles. The theory of operation, scaling, and stability is investigated using analytical and FEM models. The actuator consists of two high-density arrays of interdigitated pillars that work against a restoring force generated by an integrated flexure spring. The actuator architecture enables linear actuation with higher displacements and pull-in free actuation to prevent the in-use stiction associated with other electrostatic actuators. The pillars and springs are 3D printed together in the same structure. The pillars are coated with a gold–palladium alloy layer to form conductive electrodes. The space between the pillars is filled with liquid dielectrics for higher breakdown voltages and larger electrostatic forces due to the increase in the dielectric constant. We demonstrated a prototype actuator that produced a maximum work density of 54.6 µJ/cc and an electrical-to-mechanical energy coupling factor of 32% when actuated at 4000 V. The device was operated for more than 100,000 cycles with no degradation in displacements. The flexible polymer body was robust, allowing the actuator to operate even after high mechanical force impact, which was demonstrated by operation after drop tests. As it is scaled further, the reported actuator will enable soft and flexible muscle-like actuators that can be stacked in series and parallel to scale the resulting forces. This work paves the way for high-energy density actuators for microrobotic applications.
