Design and Simulation of a Novel Magnetic Microactuator for Microrobots in Lab-On-a-Chip Applications

This article presents the design of a magnetic microactuator comprising soft magnetic material blocks and flexible beams. The modular layout of the proposed microactuator promotes scalability towards different microrobotic applications using low magnetic fields.  The presented microactuator consists of three soft magnetic material (Ni-Fe 4750) blocks connected together via two Polydimethylsiloxane (PDMS) semi-circular beams. A detailed design approach is highlighted giving considerations toward compactness, range of motion and force characteristics of the actuator. The actuator displacement and force characteristics are approximately linear in the magnetic field strength range of 80-160 kA/m. It can achieve maximum displacements of 111.6 µm (at 160 kA/m) during extension and 10.7 µm (at 80 kA/m) during contraction under no-load condition. The maximum force output of the microactuator, computed through a contact simulation, was 404.3 nN at a magnetic field strength of 160 kA/m. The microactuator achieved stroke angles up to 18.4 in a study where the microactuator was integrated with a swimming microrobot executing rowing motion using an artificial appendage, providing insight into the capabilities of actuating untethered microrobots

System-Engineered Miniaturized Robots: From Structure to Intelligence

The development of small machines, once envisioned by Feynman decades ago, has stimulated significant research in materials science, robotics, and computer science. Over the past years, the field of miniaturized robotics has rapidly expanded with many research groups contributing to the numerous challenges inherent to this field. Smart materials have played a particularly important role as they have imparted miniaturized robots with new functionalities and distinct capabilities. However, despite all efforts and many available soft materials and innovative technologies, a fully autonomous system-engineered miniaturized robot (SEMR) of any practical relevance has not been developed yet. In this review, the foundation of SEMRs is discussed and six main areas (structure, motion, sensing, actuation, energy, and intelligence) which require particular efforts to push the frontiers of SEMRs further are identified. During the past decade, miniaturized robotic research has mainly relied on simplicity in design, and fabrication. A careful examination of current SEMRs that are physically, mechanically, and electrically engineered shows that they fall short in many ways concerning miniaturization, full-scale integration, and self-sufficiency. Some of these issues have been identified in this review. Some are inevitably yet to be explored, thus, allowing to set the stage for the next generation of intelligent, and autonomously operating SEMRs

Solar-powered shape-changing origami microfliers

Using wind to disperse microfliers that fall like seeds and leaves can help automate large-scale sensor deployments. Here, we present battery-free microfliers that can change shape in mid-air to vary their dispersal distance. We design origami microfliers using bi-stable leaf-out structures and uncover an important property: a simple change in the shape of these origami structures causes two dramatically different falling behaviors. When unfolded and flat, the microfliers exhibit a tumbling behavior that increases lateral displacement in the wind. When folded inward, their orientation is stabilized, resulting in a downward descent that is less influenced by wind. To electronically transition between these two shapes, we designed a low-power electromagnetic actuator that produces peak forces of up to 200 millinewtons within 25 milliseconds while powered by solar cells. We fabricated a circuit directly on the folded origami structure that includes a programmable microcontroller, Bluetooth radio, solar power harvesting circuit, a pressure sensor to estimate altitude and a temperature sensor. Outdoor evaluations show that our 414 milligram origami microfliers are able to electronically change their shape mid-air, travel up to 98 meters in a light breeze, and wirelessly transmit data via Bluetooth up to 60 meters away, using only power collected from the sun.Comment: This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science Robotics on September 13, 2023. DOI: 10.1126/scirobotics.adg427

Capsule endoscopy of the future: What's on the horizon?

Capsule endoscopes have evolved from passively moving diagnostic devices to actively moving systems with potential therapeutic capability. In this review, we will discuss the state of the art, define the current shortcomings of capsule endoscopy, and address research areas that aim to overcome said shortcomings. Developments in capsule mobility schemes are emphasized in this text, with magnetic actuation being the most promising endeavor. Research groups are working to integrate sensor data and fuse it with robotic control to outperform today's standard invasive procedures, but in a less intrusive manner. With recent advances in areas such as mobility, drug delivery, and therapeutics, we foresee a translation of interventional capsule technology from the bench-top to the clinical setting within the next 10 years

Microrobots for wafer scale microfactory: design fabrication integration and control.

Future assembly technologies will involve higher automation levels, in order to satisfy increased micro scale or nano scale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to micro-electronics and MEMS industries, but less so in nanotechnology. With the bloom of nanotechnology ever since the 1990s, newly designed products with new materials, coatings and nanoparticles are gradually entering everyone’s life, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than with top-down robotic assembly. This is due to considerations of volume handling of large quantities of components, and the high cost associated to top-down manipulation with the required precision. However, the bottom-up manufacturing methods have certain limitations, such as components need to have pre-define shapes and surface coatings, and the number of assembly components is limited to very few. For example, in the case of self-assembly of nano-cubes with origami design, post-assembly manipulation of cubes in large quantities and cost-efficiency is still challenging. In this thesis, we envision a new paradigm for nano scale assembly, realized with the help of a wafer-scale microfactory containing large numbers of MEMS microrobots. These robots will work together to enhance the throughput of the factory, while their cost will be reduced when compared to conventional nano positioners. To fulfill the microfactory vision, numerous challenges related to design, power, control and nanoscale task completion by these microrobots must be overcome. In this work, we study three types of microrobots for the microfactory: a world’s first laser-driven micrometer-size locomotor called ChevBot，a stationary millimeter-size robotic arm, called Solid Articulated Four Axes Microrobot (sAFAM), and a light-powered centimeter-size crawler microrobot called SolarPede. The ChevBot can perform autonomous navigation and positioning on a dry surface with the guidance of a laser beam. The sAFAM has been designed to perform nano positioning in four degrees of freedom, and nanoscale tasks such as indentation, and manipulation. And the SolarPede serves as a mobile workspace or transporter in the microfactory environment

Wireless Tagging and Actuation with Shaped Magnetoelastic Transducers.

The promise and the challenges of patterned, micro-scale magnetoelastic transducers and their integration with silicon is the focus of this thesis. As demonstrations, wireless magnetoelastic chip-scale resonant rotary motors and miniaturized magnetoelastic tags are investigated. The motors consist of a magnetoelastically-actuated stator, a silicon rotor, a “hub” structure, and DC and AC coils. Two generations are described. The first-generation motor uses a stator with a bilayer of silicon (ø8 mm x 65 µm thick) and magnetoelastic foil (Metglas™ 2826MB bulk foil, ø8 mm x 25 µm thick). The motor provides bi-directional rotation capability, and typical resonant frequencies of the clockwise and counterclockwise modes are 6.1 kHz and 7.9 kHz, respectively. The counterclockwise mode provides a rotation rate of ≈100 rpm, start torque of 30 nN∙m, a step size of 74 milli-degree and a capability for driving a 100 mg payload while a 8 Oe DC and a 6 Oe-amplitude AC magnetic field are applied. The second-generation of motors includes bilayer standing wave and traveling wave designs (ø5 mm stators) with integrated capacitive sensors for real-time position measurement and speed estimation. Clockwise and counterclockwise mode shapes with resonant frequencies of 12 kHz and 22.4 kHz, respectively, are measured for the standing wave motor. Two mode shapes (with π/2 spatial phase difference) at resonant frequencies of 30.2 kHz and 31.7 kHz are measured for the traveling wave motor. The wireless actuation capability and the hybrid integration of the bulk magnetoelastic material with silicon show promise for use in many microsystems. A lithographically patterned, frame-suspended hexagonal magnetoelastic tag design (ø1.3 mm x 27 µm thick) is also investigated. These tags provide ≈75x signal amplitude improvement compared to a non-suspended disc tag, while occupying ≈100x smaller area than typical commercial ribbon tags. Signal strength can also be boosted by taking advantage of tag signal superposition. Linear signal superposition of the response has been experimentally measured for clustered sets of frame-suspended tags that include as many as 500 units. Miniaturized tags with sufficient signal strength may enable new applications, such as distributing the tags into a network of cracks and subsequently mapping the distribution.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108961/1/juntang_1.pd

Vibrational energy harvesting for sensors in vehicles

The miniaturization of semiconductor technology and reduction in power requirements have begun to enable wireless self-sufficient devices, powered by ambient energy. To date the primary application lies in generating and transmitting sensory data. The number of sensors and their applications in automotive vehicles has grown drastically in the last decade, a trend that seems to continue still. Wireless self-powered sensors can facilitate current sensor systems by removing the need for cabling and may enable additional applications. These systems have the potential to provide new avenues of optimization in safety and performance.This thesis delves into the topic of vibrations as ambient energy source, primarily for sensors in automotive vehicles. The transduction of small amounts of vibrational, or kinetic, energy to electrical power, also known as vibrational energy harvesting, is an extensive field of research with a plethora of inventions. A short review is given for energy harvesters, in an automotive context, utilizing transduction through either the piezoelectric effect or magnetic induction. Two practical examples, for ambient vibration harvesting in vehicles, are described in more detail. The first is a piezoelectric beam for powering a strain sensor on the engines rotating flexplate. It makes combined use of centrifugal force, gravitational pull and random vibrations to enhance performance and reduce required system size. The simulated power output is 370 \ub5W at a rotation frequency of 10.5 Hz, with a bandwidth of 2.44 Hz. The second example is an energy harvesting unit placed on a belt buckle. It implements magnetic induction by the novel concept of a spring balance air gap of a magnetic circuit, to efficiently harvest minute vibrations. Simulations show the potential to achieve 52 \ub5W under normal road conditions driving at 70 km/h. Theoretical modeling of these systems is also addressed. Fundamental descriptions of the lumped and distributed models are given. Based on the lumped models of the piezoelectric energy harvester (PEH) and the electromagnetic energy harvester (EMEH), a unified model is described and analyzed. New insights are gained regarding the pros and cons of the two types of energy harvester run at either resonance or anti-resonance. A numerical solution is given for the exact boundary of dimensionless quality factor and dimensionless intrinsic resistance, at which the system begins to exhibit anti-resonance. Regarding the maximum achievable power, the typical PEH is favored when running the system in anti-resonance and the typical EMEH is favored at resonance. The described modeling considers all parameters of the lumped model and thus provides a useful tool for developing vibrational energy harvester prototypes

Magnetically Driven Micro and Nanorobots

Manipulation and navigation of micro and nanoswimmers in different fluid environments can be achieved by chemicals, external fields, or even motile cells. Many researchers have selected magnetic fields as the active external actuation source based on the advantageous features of this actuation strategy such as remote and spatiotemporal control, fuel-free, high degree of reconfigurability, programmability, recyclability, and versatility. This review introduces fundamental concepts and advantages of magnetic micro/nanorobots (termed here as "MagRobots") as well as basic knowledge of magnetic fields and magnetic materials, setups for magnetic manipulation, magnetic field configurations, and symmetry-breaking strategies for effective movement. These concepts are discussed to describe the interactions between micro/nanorobots and magnetic fields. Actuation mechanisms of flagella-inspired MagRobots (i.e., corkscrew-like motion and traveling-wave locomotion/ciliary stroke motion) and surface walkers (i.e., surface-assisted motion), applications of magnetic fields in other propulsion approaches, and magnetic stimulation of micro/nanorobots beyond motion are provided followed by fabrication techniques for (quasi)spherical, helical, flexible, wire-like, and biohybrid MagRobots. Applications of MagRobots in targeted drug/gene delivery, cell manipulation, minimally invasive surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery, pollution removal for environmental remediation, and (bio)sensing are also reviewed. Finally, current challenges and future perspectives for the development of magnetically powered miniaturized motors are discussed

Frequency-controlled wireless passive microfluidic devices

Microfluidics is a promising technology that is increasingly attracting the attention of researchers due to its high efficiency and low-cost features. Micropumps, micromixers, and microvalves have been widely applied in various biomedical applications due to their compact size and precise dosage controllability. Nevertheless, despite the vast amount of research reported in this research area, the ability to implement these devices in portable and implantable applications is still limited. To date, such devices are constricted to the use of wires, or on-board power supplies, such as batteries. This thesis presents novel techniques that allow wireless control of passive microfluidic devices using an external radiofrequency magnetic field utilizing thermopneumatic principle. Three microfluidic devices are designed and developed to perform within the range of implantable drug-delivery devices. To demonstrate the wireless control of microfluidic devices, a wireless implantable thermopneumatic micropump is presented. Thermopneumatic pumping with a maximum flow rate of 2.86 μL/min is realized using a planar wirelessly-controlled passive inductor-capacitor heater. Then, this principle was extended in order to demonstrate the selective wireless control of multiple passive heaters. A passive wirelessly-controlled thermopneumatic zigzag micromixer is developed as a mean of a multiple drug delivery device. A maximum mixing efficiency of 96.1% is achieved by selectively activating two passive wireless planar inductor-capacitor heaters that have different resonant frequency values. To eliminate the heat associated with aforementioned wireless devices, a wireless piezoelectric normally-closed microvalve for drug delivery applications is developed. A piezoelectric diaphragm is operated wirelessly using the wireless power that is transferred from an external magnetic field. Valving is achieved with a percentage error as low as 3.11% in a 3 days long-term functionality test. The developed devices present a promising implementation of the reported wireless actuation principles in various portable and implantable biomedical applications, such as drug delivery, analytical assays, and cell lysis devices

Study and development of a magnetic steering system for microrobots

In a close future micro-scaled untethered robots might be able to access small spaces inside the human body, currently reachable only by using invasive surgical methods, thus revolutionizing future medicine. The aim of this Master Thesis work is to study and develop a system that can exploit static magnetic fields and gradients to steer purpose-developed microrobots. A concept of the device for the generation of magnetic fields is first elaborated, moving from the state-of-art systems based on Helmholtz and Maxwell coils, which can generate, respectively, nearly uniform magnetic fields and gradients. A uniform magnetic field can be used to orient a magnetic or magnetisable object, aligning it with the direction of the field, while a uniform magnetic gradient can be used to shift such an object. The developed system is formed by two coils in the Maxwell geometrical configuration and independently powered in order to generate a uniform magnetic gradient, a quasi-uniform magnetic field or a superimposition of the two, reducing the overall complexity of the hardware with respect to the systems also employing Helmholtz coils. An analytical model of the on-axis magnetic field generated by the device and a finite element model of the field in the workspace are developed. Three microrobot prototypes are then considered: a millimetre-sized NdFeB cylindrical permanent magnet, which allows to test the maximum performances of the developed device, a polymeric microbead, which is more compatible with biomedical applications but less reactive to magnetic fields than a permanent magnet, and a polymeric nanofilm, which allows to test the steering of very anisotropic shapes, both containing iron oxide nanoparticles. Models of their interaction with magnetic fields are presented. Furthermore, a model of the motion of the three prototypes employing the developed magnetic device is presented. The experimental set up is described, including the two coils and their support backing, the monitoring and powering circuitry and a software kit containing four graphical user interfaces for the calibration and validation of the system. After a set of trials performed for the calibration of the magnetic-field-generating device, the system is tested in steering the microrobot prototypes. The extrapolated data are compared to the behaviours predicted by the magnetic motion models. The abilities of the magnetic steering system and its main limits are finally examined, suggesting possible improvements of both the magnetic device and the microrobots in order to enhance their control and manipulation. In particular indications for developing the next-generation of wireless magnetically-actuated microrobots and the relative steering systems are extrapolated