Electrochemical micromachining (micro-ECM) is an unconventional micromachining technology that has capability to fabricate high aspect ratio micro-holes, micro-cavities, micro-channels and grooves on ...conductive and difficult-to-cut materials. Both academia and industry have the consensus that it offers promising machining performance especially in terms of high surface finish, no tool wear and absence of thermally induced defects. Furthermore in order to machine novel materials with extreme properties, novel hybrid electrochemical micromachining technologies are under development. With these hybrid micro-ECM technologies, capabilities of micro-ECM can be expanded by combining it with other processes. To fully exploit the potential as well as improve micro-ECM technology and related hybrid processes, a wide spectrum of multidisciplinary knowledge is needed. The present review systematically discusses process capabilities and research developments of electrochemical micromachining and its hybrid variants considering knowledge of both basic and applied research fields. After few introductory review articles in prior state of the art, this review fills an important gap in research literature by presenting first time an extended literature source with a wide coverage of recent research developments in electrochemical micromachining technology and its hybrid variants. This paper outlines the research and engineering developments in electrochemical micromachining technology and its hybrid variants, review of the related concepts, aspects of tooling, advanced process capabilities and process energy sources. It also provides new sights into technological understanding of micro-ECM technology which will be helpful in future engineering developments of this technology.
•The studies related to electrochemical micromachining and its hybrid variants have been reviewed.•Both fundamental and applied research developments have been presented.•Future research potential of micro-ECM and its hybrid variants is pointed.
This paper proposes a novel tool-based hybrid laser-ECM process which exploits synergy of laser and electrochemical process energies along the same machining axis, thereby enhancing the potential of ...both processes while compensating and minimizing their limitations. This process combines features from jet-ECM and water jet guided laser processes into a new micromachining process. In this study, details of this tool-based hybrid laser-electrochemical micromachining process are presented and an experimental study on process-material interaction is performed using Inconel IN718 as workpiece material. According to the experimental results, material removal rates of the order of 0.6 mm3/min are obtained. It has been observed that while the process response is material-dependent as well as ECM parameter dependent, the effective laser pulse energy reaching the workpiece surface is the main factor influencing the surface characteristics. Additionally, the electrolyte flow rate affects material removal and also influences laser coupling into the tool-electrode. It has been observed that within a specific process window i.e. pulse-energy 30–45 μJ, flow rate 32–48 ml/min, IEG 20–30 μm, voltage 20–25 V; high quality surfaces are observed with less defects. At pulse energies higher than 60 μJ, the process speed becomes higher but the surface becomes rough due to combined material removal mechanisms taking place. Furthermore, metallographic investigations on the machined surface reveal presence of multiple removal mechanisms such as laser removal, laser assisted electrochemical removal and electrochemical removal depending on the applied laser pulse energy. Overall, this study has shown that hybrid laser-electrochemical micromachining has a high potential to machine advanced metallic alloys with conductivity variations even for high aspect ratio features and needs further research developments.
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•A novel tool-based hybrid laser-electrochemical micromachining process is presented.•Significant advancements in hardware development and process execution of hybrid laser-ECM process.•Experimental realization of hybrid laser-ECM technology is presented.•Variation of process response with process parameters are presented, process windows are highlighted and related mechanisms are explained.•Process response on different materials is also presented thereby broadening material processing window of this technology.
The 20th century's robotic systems have been made from stiff materials, and much of the developments have pursued ever more accurate and dynamic robots, which thrive in industrial automation, and ...will probably continue to do so for decades to come. However, the 21st century's robotic legacy may very well become that of soft robots. This emerging domain is characterized by continuous soft structures that simultaneously fulfill the role of robotic link and actuator, where prime focus is on design and fabrication of robotic hardware instead of software control. These robots are anticipated to take a prominent role in delicate tasks where classic robots fail, such as in minimally invasive surgery, active prosthetics, and automation tasks involving delicate irregular objects. Central to the development of these robots is the fabrication of soft actuators. This article reviews a particularly attractive type of soft actuators that are driven by pressurized fluids. These actuators have recently gained traction on the one hand due to the technology push from better simulation tools and new manufacturing technologies, and on the other hand by a market pull from applications. This paper provides an overview of the different advanced soft actuator configurations, their design, fabrication, and applications.
The 21st century's robotic legacy may very well become that of soft robots, which show remarkable features superior to those of conventional robots in tasks requiring delicate manipulation and a high degree of maneuverability. This review discusses a particular type of soft actuators—elastic inflatable actuators—which are driven by pressurized fluids and allow for straightforward integration in soft robotics.
Retinal Vein Occlusion (RVO) is a blinding disease caused by one or more occluded retinal veins. Current treatment methods only focus on symptom mitigation rather than targeting a solution for the ...root cause of the disorder. Retinal vein cannulation is an experimental eye surgical procedure which could potentially cure RVO. Its goal is to dissolve the occlusion by injecting an anticoagulant directly into the blocked vein. Given the scale and the fragility of retinal veins on one end and surgeons’ limited positioning precision on the other, performing this procedure manually is considered to be too risky. The authors have been developing robotic devices and instruments to assist surgeons in performing this therapy in a safe and successful manner. This work reports on the clinical translation of the technology, resulting in the world-first in-human robot-assisted retinal vein cannulation. Four RVO patients have been treated with the technology in the context of a phase I clinical trial. The results show that it is technically feasible to safely inject an anticoagulant into a
100
μ
m
-thick retinal vein of an RVO patient for a period of 10 min with the aid of the presented robotic technology and instrumentation.
In the ever advancing field of minimally invasive surgery, flexible instruments with local degrees of freedom are needed to navigate through the intricate topologies of the human body. Although cable ...or concentric tube driven solutions have proven their merits in this field, they are inadequate for realizing small bending radii and suffer from friction, which is detrimental when automation is envisioned. Soft robotic actuators with locally actuated degrees of freedom are foreseen to fill in this void, where elastic inflatable actuators are very promising due to their S3-principle, being Small, Soft and Safe. This paper reports on the characterization of a chip-on-tip endoscope, consisting out of a soft robotic pneumatic bending microactuator equipped with a 1.1 × 1.1 mm
2
CMOS camera. As such, the total diameter of the endoscope measures 1.66 mm. To show the feasibility of using this system in a surgical environment, a preliminary test on an eye mock-up is conducted.
Electrochemical jet processing encompasses a group of non-contact and ‘tool-less’ technologies, relying on localised electrolyte jets to affect changes to the workpiece in a site-specific manner. ...This is achieved without thermally or mechanically modifying the underlying material giving rise to a unique class of manufacturing methods. Jet techniques have been applied to remove and deposit material selectively, for example to machine microscale pits and grooves, to process larger surface areas, and to selectively coat materials through a variety of accretion phenomena. The jet itself also has the potential to serve as analysis/metrology tool. The potential to unify a broad range of site-specific manufacturing methods under one platform presents a unique opportunity to enable bespoke programmable surface geometries, finishes and compositions, guided by design and independent of material precondition. This review seeks to enrich the literature by drawing together these interdisciplinary research avenues into a single extensive but critical literature survey, incorporating the process fundamentals and theory, recent developments, and applications of jet processing methods, including hybrid jet processes. Finally, this review attempts to provide new insight and propose the direction of future research with the view to enhancing the areas in which electrochemical jet processes can add value on the factory floor and become widely applied industrial practice.
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•The state-of-the-art in electrochemical jet processes is discussed, with emphasis on fundamentals and applications.•Mechanisms of removal, accretion, and surface modification with electrolyte jets are explored.•Investigations of effects of common parameters on typical process outputs are critically reviewed.•Prospective research areas for electrochemical jet processes are discussed in the context of topical manufacturing themes.
Soft robots are an interesting alternative for classic rigid robots in applications requiring interaction with organisms or delicate objects. Elastic inflatable actuators are one of the preferred ...actuation mechanisms for soft robots since they are intrinsically safe and soft. However, these pneumatic actuators each require a dedicated pressure supply and valve to drive and control their actuation sequence. Because of the relatively large size of pressure supplies and valves compared to electrical leads and electronic controllers, tethering pneumatic soft robots with multiple degrees of freedom is bulky and unpractical. Here, a new approach is described to embed hardware intelligence in soft robots where multiple actuators are attached to the same pressure supply, and their actuation sequence is programmed by the interaction between nonlinear actuators and passive flow restrictions. How to model this hardware sequencing is discussed, and it is demonstrated on an 8‐degree‐of‐freedom walking robot where each limb comprises two actuators with a sequence embedded in their hardware. The robot is able to carry pay loads of 800 g in addition to its own weight and is able to walk at travel speeds of 3 body lengths per minute, without the need for complex on‐board valves or bulky tethers.
The interaction between nonlinear balloon‐type actuators and interconnecting flow restrictions enables arbitrary actuator sequencing. This hardware sequencing enables the multitude of pressure supply tubes in inflatable soft robotics to be cut down. An eight‐degree‐of‐freedom walking robot is tested to demonstrate this hardware sequencing strategy.
Polycaprolactone and poly-l-lactide-
-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them ...particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific environment and mechanical loading in the intestinal lumen pose harsh boundary conditions on the design of these devices, and little is known about the degradation of those mechanical properties in small intestinal fluids. Here, we perform tensile tests on injection molded samples of both polymers during in vitro degradation of up to 70 days in human intestinal fluids. We report on yield stress, Young's modulus, elongation at break and viscoelastic parameters describing both materials at regular time steps during the degradation. These characteristics are bench-marked against degradation studies of the same materials in other media. As a result, we offer time dependent mechanical properties that can be readily used for the development of medical devices that operate in the small intestine.
Arrays of beating cilia emerged in nature as one of the most efficient propulsion mechanisms at a small scale, and are omnipresent in microorganisms. Previous attempts at mimicking these systems have ...foundered against the complexity of fabricating small-scale cilia exhibiting complex beating motions. In this paper, we propose for the first time arrays of pneumatically-actuated artificial cilia that are able to address some of these issues. These artificial cilia arrays consist of six highly flexible silicone rubber actuators with a diameter of 1 mm and a length of 8 mm that can be actuated independently from each other. In an experimental setup, the effects of the driving frequency, phase difference and duty cycle on the net flow in a closed-loop channel have been studied. Net fluid speeds of up to 19 mm s(-1) have been measured. Further, it is possible to invert the flow direction by simply changing the driving frequency or by changing the duty cycle of the driving block pulse pressure wave without changing the bending direction of the cilia. Using PIV measurements, we corroborate for the first time existing mathematical models of cilia arrays to measurements on prototypes.
The controllability and consistency in the fabrication of micro-textures on large-scale remains a challenge for existing production processes. Mask electrolyte jet machining (MEJM) is an alternative ...to Jet-ECM for controllable and high-throughput surface microfabrication with more consistency of dimensional tolerances. This hybrid configuration combines the high-throughput of masked-ECM and the adjustable flow-field of jet-ECM. In this work, a duckbill jet nozzle was introduced to make MEJM more capable of batch micro-structuring. A multiphysics model was built to simulate the distribution of electrochemical reaction ions, the current density distribution, and the evolution of the shape of the machined cavity. Experimental investigations are presented showing the influence of the machining voltage and nozzle moving speed on the micro cavity. Several 35×35 micro cavity arrays with a diameter of 11.73-24.92 μm and depth of 7.24-15.86 μm are generated on 304 stainless steel.
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