Traditional shape adjustment methods for large high-precision cable network structures usually use many actuators and are only applicable to predictable shape distortions. To this end, a new method, namely, the minimum residual nodal displacement method, for optimal shape adjustment of large high-precision cable network structures is developed. The new shape adjustment method can significantly reduce shape distortion of a cable network structure by automatically placing a small number of actuators at optimal locations. This new method is applicable to cable network structures under both predictable and unpredictable shape distortions, and can determine the minimum number of actuators needed to satisfy prescribed design requirement for surface accuracy. In this method, a simple linear relationship between nodal displacements, external loads, and undeformed member lengths of a cable network structure is established, and residual nodal displacement of the structure is minimized. The effectiveness of this new method is proved in numerical simulation results, where a planar cable network structure and a reconfigurable deployable mesh reflector are investigated.

Micro-, and milli-scale robots have emerged as next generation of intelligent technology for minimally invasive diagnosis and treatment. Recent minimally invasive interventions call for robots that work as tiny "surgeons" or drug delivery "vehicles" to achieve inner body diagnostic, surgical, and therapeutic practices, without any trauma or discomfort. Most traditional medical robots are large, and lack effective locomotion design, which prevent them from entering small entrances and moving smoothly in small working areas, such as long and narrow passages. Presented in this paper is a design of an innovative milli-scale deployable tensegrity microrobot for minimally invasive interventions. The robot is made of a deployable tensegrity structure integrated by self-stress. A folded size of the robot is small for easily entering a desired working area with a small entrance. When deployed, the tensegrity body of the robot displays lightweight and high stiffness to sustain loads and prevent damages when burrowing through tightly packed tissues or high-pressure environments. Locomotion of the tensegrity microrobot is designed to mimic a crawling motion of an earthworm, which grants the robot an ability to move well through small working areas. The robot is also an untethered agent. Morphing for deployment and locomotion of the robot is actuated by magnetic forces generated by its active members that serve as electromagnetic coils.

This paper presents the proof-of-concept study on a non-invasive microrobot technology that incorporates the frontier submillimeter magnetic microrobot with the burgeoning photoacoustic imaging. Tracking one single untethered magnetic microrobot through the integrated ultrasound and photoacoustic (USPA) imaging will allow for real non-invasive microrobot operation in the non-transparent biological tissues. In this preliminary work, the magnetic microrobot prototypes are made from photoresist mixed with nickel particles. Single microrobot agent is set in fluid environment bounded by nontransparent phantom. The experimental results prove that the current microrobot prototypes down to smaller than 100 μm can be detected by USPA imaging through 25 mm thick opaque phantom, both statically and in a motion of speed approximately 1.2 mm/s. The further investigation of this concept will advance the integration of both non-invasive magnetic manipulation and USPA tracking of the microrobot, targeting the real biomedical applications in the tiny enclosed workspace.

This paper presents the innovative integration of both frontier submillimeter magnetic microrobot and integrated ultrasound and photoacoustic (USPA) imaging. The integrative technique will allow for potential real non-invasive microrobot operation in deep biological tissue for biomedical applications. In this study, the magnetic microrobot prototypes are fabricated in series of different sizes through patterning SU-8 photoresist mixed with nickel particles. In order for proof-of-concept, the magnetic microrobot is actuated by a static magnetic field, which is produced by a multiple magnet cone array. As mimicking the opaque biological environment, the magnetic microrobot is placed in a fluid environment bounded by a non-transparent phantom. The USPA imaging system consists of a laser system to illuminate working space and an ultrasound system to receive the acoustic signal generated by imaging object due to photonic signal absorption. The experimental tests prove that the USPA imaging protocol can detect single microrobot smaller than 100 μm through the 15 mm thick opaque phantom. The imaging test has been accomplished both statically and in a motion of approximately 2.0 mm/s. Further investigation of this concept will focus on the collaboration of photoacoustic imaging and magnetic manipulation of microrobot under real biological fluid media.

The next generation of intelligent robotic systems has been envisioned as micro-scale mobile and externally controllable robots. Visualization of such small size microrobots to track their motion in nontransparent medium such as human tissue remains a major challenge, limiting translation into clinical applications. Herein, we present a novel, non-invasive, real-time imaging method by integrating ultrasound (US) and photoacoustic (PA) imaging modalities for tracking and detecting the motion of a single microrobot in deep biological tissue. We developed and evaluated a prototyped PA-guided magnetic microrobot tracking system. The microrobots are fabricated using photoresist mixed with nickel (Ni) particles. The microrobot motion was controlled using an externally applied magnetic field. Our experimental results evaluated the capabilities of PA imaging in visualizing and tracking microrobots in opaque tissue and tissue-mimicking phantoms. The results also demonstrate the ability of PA imaging in detecting a microrobot with the sizes less than the minimum detectable size by US imaging (down to 50 µm). The spectroscopic PA imaging studies determined an optimal wavelength (700 nm) for imaging microrobots with embedded Ni particles in oxygenated (fresh) human blood. In addition, we examined the ability of PA imaging to detect the microrobots through a nontransparent tissue mimic and at a depth of 25 mm, where conventional optical methods are unable to be used in tracking the objects. These initial results demonstrate the feasibility of an integrated US and PA imaging method to push the boundaries of microrobot applications into translational applications.

This paper presents the proof-of-concept study on a non-invasive tracking of submillimeter sized micro-robotic objects by using combined ultrasound and photoacoustic imaging. Tracking one single microscale untethered magnetic microrobot through the integrated ultrasound and photoacoustic (USPA) imaging will allow for accurate real-time controlling the manipulation of the microrobot in optically non-transparent biological tissues. In this work, the magnetic microrobot prototypes are made from photoresist mixed with nickel particles. Single microrobot agent is set in a fluid environment bounded by an opaque phantom. The experimental results prove that the current microrobot prototypes smaller than 100 μm can be detected by USPA imaging through 15 mm thick opaque phantom, both statically and in a motion of speed approximately 1.5 mm/s. The further investigation of this concept will advance the integration of both non-invasive magnetic manipulation and USPA tracking of the microrobot, targeting the real biomedical applications in the tiny enclosed workspaces.

This paper presents a microforce-sensing mobile microrobot (mu FSMM) for use in automated micromanipulation tasks. The design consists of a planar vision-based microforce sensor end-effector, while the microrobot body is made of chemically etched nickel that is driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, the mobility and in situ force-sensing capabilities are verified through real-time, closed loop, force controlled manipulation tests with automated path planning and navigation. The calibrated stiffness of the microforce sensor end-effectors fabricated is on the order of 10(-3) N/m. The online (real time) force-sensing resolution is approximately 1.5 mu N. The sensing range is 0-20 mu N along the two planar directions. In automated micromanipulation experiments with a microcomponent, the mu FSMM utilizes real-time force control to apply a prescribed force of 6 mu N to a desired location on a fixed microobject. Similarly, in another automated micromanipulation experiment, the mu FSMM demonstrates the use of real-time force control to limit the manipulation forces experienced by the microobject to remain below a threshold of 12 mu N. Note to Practitioners-This paper was motivated by recent interest single-cell biological micromanipulation tasks that seek to understand the role of environmental forces on the mechanics of cell development (mechanobiology) and the biological mechanisms that control such behavior (mechanotransduction). In addition, tissue engineering applications require the safe micromanipulation of single cells to desired locations in the workspace for growing tissue scaffolds. The mu FSMM presented here can be easily inserted into existing biological testbeds to use for these aforementioned applications. The designed magnetic coil system is compatible with standard inverted optical microscopes, while a digital camera for real-time image processing is already standard in these testbeds. The developed software interface can be used to prescribe automated microforce controlled manipulations of single cells and tissues in the workspace to carry out these aforementioned tasks. This paper is also suitable for carrying out general automated micromanipulation and microassembly tasks with advanced manufacturing applications.

Mechanical engineering seniors at Lawrence Technological University (LTU) complete a capstone design project: either an SAE collegiate design series (CDS) competition or an industry-sponsored project (ISP). Starting in 2015, the LTU CDS advisors worked together to redesign the five-credit three-semester sequence. The overall goals of the modifications were to improve student design, project management and communication skills; integrate SAE CDS projects into the actual class time; and increase faculty advisor involvement in the classroom. In parallel with senior design modifications, faculty recently completed a multiyear process to incorporate active and collaborative learning (ACL), problem-based learning (PBL), and entrepreneurially minded learning (EML) into the engineering curriculum. Leveraging the curriculum-wide course modifications, the CDS advisors also incorporated ACL and EML components into the capstone design changes. Student demonstration of example behaviors associated with an entrepreneurial mindset were assessed using student surveys in the Introduction to Projects course (the beginning of the sequence) and Competition Projects 2 course (the end of the sequence) at the conclusion of the Spring 2018 semester. The results indicate that the capstone projects are great venues for students to work collaboratively and practice entrepreneurial skills. For example, students have to “integrate information from many sources to gain insight” and need to “persist through failure” throughout this 18 month long project. Most of the students admit that they need to almost always work as a team, and also to “understand the motivations and perspectives of others.” They also agree that through the capstone design project they have improved skills in project organization, time management, and project management. The survey results will be used to guide additional development of classroom materials to better foster the entrepreneurial mindset.

This paper presents several variations of a microscale magnetic tumbling ( μ TUM) robot capable of traversing complex terrains in dry and wet environments. The robot is fabricated by photolithography techniques and consists of a polymeric body with two sections with embedded magnetic particles aligned at the ends and a middle nonmagnetic bridge section. The robot's footprint dimensions are 400 μ m × 800 μ m. Different end geometries are used to test the optimal conditions for low adhesion and increased dynamic response to an actuating external rotating magnetic field. When subjected to a magnetic field as low as 7 mT in dry conditions, this magnetic microrobot is able to operate with a tumbling locomotion mode and translate with speeds of over 60 body lengths/s (48 mm/s) in dry environments and up to 17 body lengths/s (13.6 mm/s) in wet environments. Two different tumbling modes were observed and depend on the alignment of the magnetic particles. A technique was devised to measure the magnetic particle alignment angle relative to the robot's geometry. Rotational frequency limits were observed experimentally, becoming more prohibitive as environment viscosity increases. The μ TUM's performance was studied when traversing inclined planes (up to 60°), showing promising climbing capabilities in both dry and wet conditions. Maximum open loop straight-line trajectory errors of less than 4% and 2% of the traversal distance in the vertical and horizontal directions, respectively, for the μ TUM were observed. Full directional control of μ TUM was demonstrated through the traversal of a P-shaped trajectory. Additionally, successful locomotion of the optimized μ TUM design over complex terrains was also achieved. By implementing machine vision control and/or embedding of payloads in the middle section of the robot, it is possible in the future to upgrade the current design with computer-optimized mobility through multiple environments and the ability to perform drug delivery tasks for biomedical applications.

This chapter presents our recent efforts on developing a micro-force sensing mobile microrobot (μFSMM). The design consists of a planar, vision based micro-force sensor end-effector attached to a magnetic microrobot body. The body is made of chemically etched nickel and is driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, the mobility and in-situ force sensing capabilities are verified through force controlled manipulation tests. With our current experimental testbed, this micro-scale μFSMM is able to translate with the speed up to 3 mm/s in an oil environment. The calibrated stiffness of the micro-force sensor end-effector is on the order of 10−2 N/m. The force sensing resolution is approximately 100 nN.

Autonomous manipulation at the microscale has applications in both the manufacturing and biomedical industries. However, independent actuation of multiple robots equipped with different manipulators is important for the speed and success of manipulation. In this paper, we have developed a specialized substrate with an array of microcoils that can generate local magnetic fields to control multiple microrobots independently. We have developed a physics based planning approach to compute the paths for the microrobots that can avoid obstacles and are well-suited for execution by the array of microcoils for autonomous navigation. We have demonstrated the capability of the planner with simulation experiments and the effectiveness of the microcoil array in independent actuation of the microrobots with physical experiments. The limitations of the current system are presented and a modified microcoil array is proposed and analyzed for increased performance.

In this paper, we have developed an approach for autonomous navigation of single and multiple microrobots under the influence of magnetic fields generated by electromagnetic coils. Our approach consists of three steps. First, we have developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable to be executed by the available magnetic field. Second, we have modeled the dynamics of the microrobots to develop a controller for determining the forces that need to be generated for the navigation of the robots along the trajectories at a suitable control frequency. Finally, an optimization routine is developed to determine the input currents to the electromagnetic coils that can generate the required forces for the navigation of the robots at the controller frequency. We have validated our approach by simulating two electromagnetic coil systems. The first system has four electromagnetic coils designed for actuating a single microrobot. The second system has an array of sixty-four magnetic microcoils designed for generating local magnetic fields suitable for simultaneous independent actuation of multiple microrobots.

Assembly of micro-scale objects requires us to develop manipulators that are small enough to apply small forces as well as robust enough to be controlled independently in a large number. In this paper, we have designed a specialized surface that can be utilized to control multiple microrobots with magnetic properties independently. The surface accommodates an array of planar microcoils that can create local magnetic fields to control multiple microrobots independently. We have also developed a simulation based planning approach with the offline estimation of the magnetic field generated by the microcoils to automate the motions of multiple microrobots. We have demonstrated the effectiveness of our planning approach with simulation experiments.

In this paper, we have developed an approach for independent autonomous navigation of multiple microrobots under the influence of magnetic fields and validated it experimentally. We first developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable to be executed by an available magnetic field. Second, we have modeled the dynamics of the microrobots to develop a controller for determining the forces that need to be generated for the navigation of the robots along the trajectories at a suitable control frequency. Next, an optimization routine is developed to determine the input currents to the electromagnetic coils that can generate the required forces for the navigation of the robots at the controller frequency. We then validated our approach by simulating an electromagnetic system that contains an array of sixty-four magnetic microcoils designed for generating local magnetic fields suitable for simultaneous independent actuation of multiple microrobots. Finally, we prototyped an m m -scale version of the system and present experimental results showing the validity of our approach.

The ability to control microrobots by means of magnetic fields has become of increasing interest to researchers. These robots’ ability to reach places tethered microrobots otherwise could not leads to many possible applications in the body, such as delivering drugs to targeted locations and performing biopsies. This study shows the use of shape memory polymer (SMP) to wirelessly actuate a microgripper to be used by a controllable microrobot to achieve these functions. Many smart materials were analyzed in order to find the material that most effectively would accomplish wirelessly gripping, manipulating, and releasing a microobject. Multiple microgripper designs were designed, analyzed, and constructed at a macroscale from acrylic, simulating a microscale counterpart. Simulated and experimental data were compared to determine the design that would require the least amount of inputted force and displacement from the SMP. This study shows a proposal for scaling this final design to the microscale involving experimentation with different forms of SMP in order to make the gripper actuatable in biologically relevant conditions. This technology could provide an inexpensive and effective solution for manipulating cells and other microobjects in vitro and in vivo.

Robots the size of several microns have numerous application in medicine, biology, and manufacturing. However, simultaneous control of multiple robots at this scale is difficult since the robot itself is too small to carry power, sensors, communication, and control on-board. In this paper, we have summarized different approaches, ranging from specialized robot design and fabrication to specialized ways of actuating robots, with the aim of independent control of a team/swarm of microrobots. We have also discussed the challenges for each approach. In the light of the challenges, we have proposed some directions where the future researchers can focus in order to solve the problem of independent control of a team of microrobots.

This paper presents the first microscale micro force sensing mobile microrobot. The design consists of a planar, vision-based micro force sensor end-effector, while the microrobot body is made from photoresist mixed with nickel particles that is driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, proof of concept tests are conducted to verify this microrobot prototype possessing the mobility and in-situ force sensing capabilities. This microscale micro-Force Sensing Mobile Microrobot (mu FSMM) is able to translate with the speed up to 10 mm/s in a fluid environment. The calibrated stiffness of the micro force sensor end-effector of the mu FSMM is on the order of 10(-2) N/m. The force sensing resolution with the current vision system is approximately 100 nN.

This chapter covers some fundamental work towards realizing functional mobile magnetic microrobots. First, the theoretical fundamentals of electromagnetism are presented. Second, an electromagnetic testbed design for controlling mobile magnetic microrobots is described. It is utilized to perform benchmarking tests on a simple I-bar shaped magnetic microrobot design. After benchmarking, the critical aspects for micro scale robots and two specific microrobot designs are developed addressing the application needs of biomedical and micro manufacturing tasks. They exhibit tumbling and crawling locomotion mechanisms, respectively. Finally, a magnet microrobot body and vision-based force sensor end-effector combination illustrates an approach for combining different technologies together to create the truly functional mobile magnetic microrobots of the future.

This paper presents a proof-of-concept prototype of a micro force sensing mobile microrobot. The design consists of a planar, elastic mechanism serving as computer vision-based force sensor module, while the microrobot body is made from a magnetic layer driven by a magnetic field. From observing the deformation of the elastic mechanism, manipulation forces can be determined. The deformation is tracked by a CCD camera attached to an optical microscope. This design is validated through experimental tests with a micromachined prototype. The preliminary results verify this first microrobot prototype is indeed capable of in situ force sensing. This concept can be scaled down further for next generation designs and can be designed for real biomedical applications on microscale.

Untethered submilliliter-sized robots (microrobots) are showing potential use in different industrial, manufacturing and medical applications. A particular type of these microrobots, magnetic robots, have shown improved performance in power and control capabilities compared to the other thermal and electrostatic based robots. However, the magnetic robot designs have not been assessed in a robust manner to understand the degree of control in different environments and their application feasibility. This research project seeks to develop a custom control software interface to provide a holistic tool for researchers to evaluate the microrobotic performance through advance control features. The software deliverable involved two main aspects: 1) Realtime microrobot detection and tracking through image processing, achieved through testing with different combinations of built-in tracking algorithms in OpenCV package, and 2) hardware interfacing with a microcontroller based coil control system through serial port communication for direct control of the magnetic coils. The robotic motion control was studied using error mode correction strategies to provide a robust, accurate and time efficient image stream based robotic controls. The user interface developed conducts change in brightness and rotation invariant tracking with an efficient speed of 12 frames per second and performs real-time calculation of robot’s position and orientation. It provides robust automatic control of directing microrobotic motion along the specific path waypoints entered on the images, through recursive serial bus communication. The project showcases the advanced importance and the powerful tool of image processing and microcontroller based communication in conducting the performance analysis of promising microrobotic designs.