Physical Intelligence



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Microfibers with mushroom-shaped tips for optimal adhesion

Sitti, M., Aksak, B.

2023, US Patent 11,613,674 (patent)

[BibTex]

[BibTex]


Magnetic trap system and method of navigating a microscopic device
Magnetic trap system and method of navigating a microscopic device

Son, D., Ugurlu, M., Bluemer, P., Sitti, M.

2023, US Patent App. 17/871,598 (patent)

[BibTex]


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Dry adhesives and methods for making dry adhesives

M Sitti, M. M. B. A.

2023, US Patent 11,773,298, 2023 (patent)

[BibTex]

2022


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DRY ADHESIVES AND METHODS FOR MAKING DRY ADHESIVES

Metin Sitti, Michael Murphy, Burak Aksak

December 2022, US Patent App. 17/895,334, 2022 (patent)

[BibTex]

2022

[BibTex]


Optoacoustic Tracking and Magnetic Manipulation of Cell-Sized Microrobots in Mice
Optoacoustic Tracking and Magnetic Manipulation of Cell-Sized Microrobots in Mice

Wrede, P., Degtyaruk, O., Kalva, S. K., Deán-Ben, X. L., Bozuyuk, U., Aghakhani, A., Akolpoglu, B., Sitti, M., Razansky, D.

Clinical and Translational Biophotonics, pages: TTu4B-6, 2022 (conference)

DOI [BibTex]

DOI [BibTex]


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Magnetic trap system and method of navigating a microscopic device

Sitti, M., Son, D., Bluemler, P.

2021, EP Prio. Patent App. 21 187 691.7 (patent)

[BibTex]

[BibTex]


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Heat assisted magnetic programming of soft materials

Sitti, M., Alapan, Y., Karacakol, A.

2021, International App. PCT/EP2021/060313 (patent)

[BibTex]


Scientific Report 2016 - 2021
Scientific Report 2016 - 2021
2021 (mpi_year_book)

Abstract
This report presents research done at the Max Planck Institute for Intelligent Systems from January2016 to November 2021. It is our fourth report since the founding of the institute in 2011. Dueto the fact that the upcoming evaluation is an extended one, the report covers a longer reportingperiod.This scientific report is organized as follows: we begin with an overview of the institute, includingan outline of its structure, an introduction of our latest research departments, and a presentationof our main collaborative initiatives and activities (Chapter1). The central part of the scientificreport consists of chapters on the research conducted by the institute’s departments (Chapters2to6) and its independent research groups (Chapters7 to24), as well as the work of the institute’scentral scientific facilities (Chapter25). For entities founded after January 2016, the respectivereport sections cover work done from the date of the establishment of the department, group, orfacility. These chapters are followed by a summary of selected outreach activities and scientificevents hosted by the institute (Chapter26). The scientific publications of the featured departmentsand research groups published during the 6-year review period complete this scientific report.

Scientific Report 2016 - 2021 [BibTex]

2020


Learning of sub-optimal gait controllers for magnetic walking soft millirobots
Learning of sub-optimal gait controllers for magnetic walking soft millirobots

Culha, U., Demir, S. O., Trimpe, S., Sitti, M.

In Robotics: Science and Systems XVI, pages: P070, (Editors: Toussaint, Marc and Bicchi, Antonio and Hermans, Tucker), RSS Foundation, Robotics: Science and Systems 2020 (RSS 2020), 2020 (inproceedings)

Abstract
Untethered small-scale soft robots have promising applications in minimally invasive surgery, targeted drug delivery, and bioengineering applications as they can access confined spaces in the human body. However, due to highly nonlinear soft continuum deformation kinematics, inherent stochastic variability during fabrication at the small scale, and lack of accurate models, the conventional control methods cannot be easily applied. Adaptivity of robot control is additionally crucial for medical operations, as operation environments show large variability, and robot materials may degrade or change over time,which would have deteriorating effects on the robot motion and task performance. Therefore, we propose using a probabilistic learning approach for millimeter-scale magnetic walking soft robots using Bayesian optimization (BO) and Gaussian processes (GPs). Our approach provides a data-efficient learning scheme to find controller parameters while optimizing the stride length performance of the walking soft millirobot robot within a small number of physical experiments. We demonstrate adaptation to fabrication variabilities in three different robots and to walking surfaces with different roughness. We also show an improvement in the learning performance by transferring the learning results of one robot to the others as prior information.

link (url) DOI Project Page [BibTex]

2020

link (url) DOI Project Page [BibTex]


Fibrillar structures to reduce viscous drag on aerodynamic and hydrodynamic wall surfaces
Fibrillar structures to reduce viscous drag on aerodynamic and hydrodynamic wall surfaces

Castillo, L., Aksak, B., Sitti, M.

2020, US Patent 10,830,261 (patent)

[BibTex]


Gripping apparatus and method of producing a gripping apparatus
Gripping apparatus and method of producing a gripping apparatus

Song, S., Sitti, M., Drotlef, D., Majidi, C.

Google Patents, February 2020, US Patent App. 16/610,209 (patent)

Abstract
The present invention relates to a gripping apparatus comprising a membrane; a flexible housing; with said membrane being fixedly connected to a periphery of the housing. The invention further relates to a method of producing a gripping apparatus.

[BibTex]

[BibTex]


Method and device for reversibly attaching a phase changing metal to an object
Method and device for reversibly attaching a phase changing metal to an object

Zhou Ye, G. Z. L. M. S.

US Patent Application 10675718, January 2020 (patent)

Abstract
A method for reversibly attaching a phase changing metal to an object, the method comprising the steps of: providing a substrate having at least one surface at which the phase changing metal is attached, heating the phase changing metal above a phase changing temperature at which the phase changing metal changes its phase from solid to liquid, bringing the phase changing metal, when the phase changing metal is in the liquid phase or before the phase changing metal is brought into the liquid phase, into contact with the object, permitting the phase changing metal to cool below the phase changing temperature, whereby the phase changing metal becomes solid and the object and the phase changing metal become attached to each other, reheating the phase changing metal above the phase changing temperature to liquefy the phase changing metal, and removing the substrate from the object, with the phase changing metal separating from the object and remaining with the substrate.

US Patent Application Database US Patent Application (PDF) link (url) [BibTex]


Method of actuating a shape changeable member, shape changeable member and actuating system
Method of actuating a shape changeable member, shape changeable member and actuating system

Hu, W., Lum, G. Z., Mastrangeli, M., Sitti, M.

Google Patents, January 2020, US Patent App. 16/477,593 (patent)

Abstract
The present invention relates to a method of actuating a shape changeable member of actuatable material. The invention further relates to a shape changeable member and to a system comprising such a shape changeable member and a magnetic field apparatus.

[BibTex]


Method of fabricating a shape-changeable magentic member, method of producing a shape changeable magnetic member and shape changeable magnetic member
Method of fabricating a shape-changeable magentic member, method of producing a shape changeable magnetic member and shape changeable magnetic member

Guo Zhan Lum, Z. Y. M. S.

US Patent Application 16845646, 2020 (patent)

Abstract
The present invention relates to a method of fabricating a shape-changeable magnetic member comprising a plurality of segments with each segment being able to be magnetized with a desired magnitude and orientation of magnetization, to a method of producing a shape changeable magnetic member composed of a plurality of segments and to a shape changeable magnetic member.

US Patent Application Database US Patent Application (PDF) [BibTex]


Method for producing an XUV and X-ray diffractive optic
Method for producing an XUV and X-ray diffractive optic

SANLI, U. T., Ceylan, H., Sitti, M., SCHÜTZ, G., Keskinbora, K.

2020, US Patent App. 16/979,121 (patent)

[BibTex]

[BibTex]


Towards 5-DoF control of an untethered magnetic millirobot via MRI gradient coils
Towards 5-DoF control of an untethered magnetic millirobot via MRI gradient coils

Erin, O., Antonelli, D., Tiryaki, M. E., Sitti, M.

In 2020 IEEE International Conference on Robotics and Automation (ICRA 2020), pages: 6551-6557, IEEE, Piscataway, NJ, IEEE International Conference on Robotics and Automation (ICRA 2020), 2020 (inproceedings)

DOI [BibTex]

DOI [BibTex]


Design and Development of a Lorentz Force-Based MRI-Driven Neuroendoscope
Design and Development of a Lorentz Force-Based MRI-Driven Neuroendoscope

Phelan III, M. F., Dogan, N. O., Lazovic, J., Sitti, M.

In 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pages: 9534-9541, 2020 (inproceedings)

DOI [BibTex]

DOI [BibTex]

2019


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Collective formation and cooperative function of a magnetic microrobotic swarm

Xiaoguang Dong, M. S.

IEEE, Robotics: Science and Systems, June 2019 (conference)

Abstract
Untethered magnetically actuated microrobots can access distant, enclosed and small spaces, such as inside microfluidic channels and the human body, making them appealing for minimal invasive tasks. Despite the simplicity of individual magnetic microrobots, a collective of these microrobots that can work closely and cooperatively would significantly enhance their capabilities. However, a challenge of realizing such collective magnetic microrobots is to coordinate their formations and motions with underactuated control signals. Here, we report a method that allows collective magnetic microrobots working closely and cooperatively by controlling their two-dimensional (2D) formations and collective motions in a programmable manner. The actively designed formation and intrinsic adjustable compliance within the group allow bio-inspired collective behaviors, such as navigating through cluttered environments and reconfigurable cooperative manipulation ability. These collective magnetic microrobots thus could enable potential applications in programmable self-assembly, modular robotics, swarm robotics, and biomedicine.

Collective Formation and Cooperative Function of a Magnetic Microrobotic Swarm DOI Project Page [BibTex]


A magnetically-actuated untethered jellyfish-inspired soft milliswimmer
A magnetically-actuated untethered jellyfish-inspired soft milliswimmer

(Best Paper Award)

Ziyu Ren, T. W., Hu, W.

Robotics: Science and Systems, June 2019 (conference)

Project Page [BibTex]


Wide range-sensitive, bending-insensitive pressure detection and application to wearable healthcare device
Wide range-sensitive, bending-insensitive pressure detection and application to wearable healthcare device

Kim, S., Amjadi, M., Lee, T., Jeong, Y., Kwon, D., Kim, M. S., Kim, K., Kim, T., Oh, Y. S., Park, I.

In 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), 2019 (inproceedings)

[BibTex]

[BibTex]


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Method of assembling mobile micro-machines and a mobile micro-machine

Sitti, M., Yigit, M. B., Alapan, Y., Beker, O.

2019, International Application, Sep.2019, PCT/EP2019/075564 (patent)

[BibTex]

[BibTex]


Scientific Report 2016 - 2018
Scientific Report 2016 - 2018
2019 (mpi_year_book)

Abstract
This report presents research done at the Max Planck Institute for Intelligent Systems from January 2016 to December 2018. It is our third report since the founding of the institute in 2011. This status report is organized as follows: we begin with an overview of the institute, including its organizational structure (Chapter 1). The central part of the scientific report consists of chapters on the research conducted by the institute’s departments (Chapters 2 to 5) and its independent research groups (Chapters 6 to 18), as well as the work of the institute’s central scientific facilities (Chapter 19). For entities founded after January 2016, the respective report sections cover work done from the date of the establishment of the department, group, or facility.

Scientific Report 2016 - 2018 [BibTex]


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Printing-while-moving: a new paradigm for large-scale robotic 3D printing

Tiryaki, M. E., Zhang, X., Pham, Q.

2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2019), pages: 2286-2291 , IEEE, Piscataway, NJ, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2019), 2019 (conference)

link (url) DOI [BibTex]

link (url) DOI [BibTex]


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A bio-inspired robotic fish fin with mechanosensation using conductive liquid-metal-infused soft actuators

Liu, Z., Sun, W., Ren, Z., Hu, K., Wang, T., Wen, L.

2019 IEEE 9th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER 2019), pages: 689-694, IEEE, Piscataway, NJ, IEEE 9th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER 2019) , 2019 (conference)

link (url) DOI [BibTex]

link (url) DOI [BibTex]

2018


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Enhanced non-steady gliding performance of the MultiMo-Bat through optimal airfoil configuration and control strategy

Kim, H., Woodward, M. A., Sitti, M.

In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pages: 1382-1388, 2018 (inproceedings)

Project Page [BibTex]

2018

Project Page [BibTex]


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Collectives of spinning mobile microrobots for navigation and object manipulation at the air-water interface

Wang, W., Kishore, V., Koens, L., Lauga, E., Sitti, M.

In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pages: 1-9, 2018 (inproceedings)

Project Page [BibTex]

Project Page [BibTex]


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Endo-VMFuseNet: A deep visual-magnetic sensor fusion approach for endoscopic capsule robots

Turan, M., Almalioglu, Y., Gilbert, H. B., Sari, A. E., Soylu, U., Sitti, M.

In 2018 IEEE International Conference on Robotics and Automation (ICRA), pages: 1-7, 2018 (inproceedings)

[BibTex]

[BibTex]


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Endosensorfusion: particle filtering-based multi-sensory data fusion with switching state-space model for endoscopic capsule robots

Turan, M., Almalioglu, Y., Gilbert, H., Araujo, H., Cemgil, T., Sitti, M.

In 2018 IEEE International Conference on Robotics and Automation (ICRA), pages: 1-8, 2018 (inproceedings)

[BibTex]

[BibTex]

2017


Swimming in low reynolds numbers using planar and helical flagellar waves
Swimming in low reynolds numbers using planar and helical flagellar waves

Khalil, I. S. M., Tabak, A. F., Seif, M. A., Klingner, A., Adel, B., Sitti, M.

In 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pages: 1907-1912, International Conference on Intelligent Robots and Systems, September 2017 (inproceedings)

Abstract
In travelling towards the oviducts, sperm cells undergo transitions between planar to helical flagellar propulsion by a beating tail based on the viscosity of the environment. In this work, we aim to model and mimic this behaviour in low Reynolds number fluids using externally actuated soft robotic sperms. We numerically investigate the effects of transition between planar to helical flagellar propulsion on the swimming characteristics of the robotic sperm using a model based on resistive-force theory to study the role of viscous forces on its flexible tail. Experimental results are obtained using robots that contain magnetic particles within the polymer matrix of its head and an ultra-thin flexible tail. The planar and helical flagellar propulsion are achieved using in-plane and out-of-plane uniform fields with sinusoidally varying components, respectively. We experimentally show that the swimming speed of the robotic sperm increases by a factor of 1.4 (fluid viscosity 5 Pa.s) when it undergoes a controlled transition between planar to helical flagellar propulsion, at relatively low actuation frequencies.

DOI [BibTex]

2017

DOI [BibTex]


An XY $\theta$ z flexure mechanism with optimal stiffness properties
An XY θz flexure mechanism with optimal stiffness properties

Lum, G. Z., Pham, M. T., Teo, T. J., Yang, G., Yeo, S. H., Sitti, M.

In 2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), pages: 1103-1110, July 2017 (inproceedings)

Abstract
The development of optimal XY θz flexure mechanisms, which can deliver high precision motion about the z-axis, and along the x- and y-axes is highly desirable for a wide range of micro/nano-positioning tasks pertaining to biomedical research, microscopy technologies and various industrial applications. Although maximizing the stiffness ratios is a very critical design requirement, the achievable translational and rotational stiffness ratios of existing XY θz flexure mechanisms are still restricted between 0.5 and 130. As a result, these XY θz flexure mechanisms are unable to fully optimize their workspace and capabilities to reject disturbances. Here, we present an optimal XY θz flexure mechanism, which is designed to have maximum stiffness ratios. Based on finite element analysis (FEA), it has translational stiffness ratio of 248, rotational stiffness ratio of 238 and a large workspace of 2.50 mm × 2.50 mm × 10°. Despite having such a large workspace, FEA also predicts that the proposed mechanism can still achieve a high bandwidth of 70 Hz. In comparison, the bandwidth of similar existing flexure mechanisms that can deflect more than 0.5 mm or 0.5° is typically less than 45 Hz. Hence, the high stiffness ratios of the proposed mechanism are achieved without compromising its dynamic performance. Preliminary experimental results pertaining to the mechanism's translational actuating stiffness and bandwidth were in agreement with the FEA predictions as the deviation was within 10%. In conclusion, the proposed flexure mechanism exhibits superior performance and can be used across a wide range of applications.

DOI [BibTex]

DOI [BibTex]


Positioning of drug carriers using permanent magnet-based robotic system in three-dimensional space
Positioning of drug carriers using permanent magnet-based robotic system in three-dimensional space

Khalil, I. S. M., Alfar, A., Tabak, A. F., Klingner, A., Stramigioli, S., Sitti, M.

In 2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), pages: 1117-1122, July 2017 (inproceedings)

Abstract
Magnetic control of drug carriers using systems with open-configurations is essential to enable scaling to the size of in vivo applications. In this study, we demonstrate motion control of paramagnetic microparticles in a low Reynolds number fluid, using a permanent magnet-based robotic system with an open-configuration. The microparticles are controlled in three-dimensional (3D) space using a cylindrical NdFeB magnet that is fixed to the end-effector of a robotic arm. We develop a kinematic map between the position of the microparticles and the configuration of the robotic arm, and use this map as a basis of a closed-loop control system based on the position of the microparticles. Our experimental results show the ability of the robot configuration to control the exerted field gradient on the dipole of the microparticles, and achieve positioning in 3D space with maximum error of 300 µm and 600 µm in the steady-state during setpoint and trajectory tracking, respectively.

DOI [BibTex]

DOI [BibTex]


Self-assembly of micro/nanosystems across scales and interfaces
Self-assembly of micro/nanosystems across scales and interfaces

Mastrangeli, M.

In 2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), pages: 676 - 681, IEEE, July 2017 (inproceedings)

Abstract
Steady progress in understanding and implementation are establishing self-assembly as a versatile, parallel and scalable approach to the fabrication of transducers. In this contribution, I illustrate the principles and reach of self-assembly with three applications at different scales - namely, the capillary self-alignment of millimetric components, the sealing of liquid-filled polymeric microcapsules, and the accurate capillary assembly of single nanoparticles - and propose foreseeable directions for further developments.

link (url) DOI [BibTex]

link (url) DOI [BibTex]


Dynamic analysis on hexapedal water-running robot with compliant joints
Dynamic analysis on hexapedal water-running robot with compliant joints

Kim, H., Liu, Y., Jeong, K., Sitti, M., Seo, T.

In 2017 14th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI), pages: 250-251, June 2017 (inproceedings)

Abstract
The dynamic analysis has been considered as one of the important design methods to design robots. In this research, we derive dynamic equation of hexapedal water-running robot to design compliant joints. The compliant joints that connect three bodies will be used to improve mobility and stability of water-running motion's pitch behavior. We considered all of parts as rigid body including links of six Klann mechanisms and three main frames. And then, we derived dynamic equation by using the Lagrangian method with external force of the water. We are expecting that the dynamic analysis is going to be used to design parts of the water running robot.

DOI [BibTex]

DOI [BibTex]


Design and actuation of a magnetic millirobot under a constant unidirectional magnetic field
Design and actuation of a magnetic millirobot under a constant unidirectional magnetic field

Erin, O., Giltinan, J., Tsai, L., Sitti, M.

In 2017 IEEE International Conference on Robotics and Automation (ICRA), 2017 IEEE International Conference on Robotics and Automation (ICRA), pages: 3404-3410, IEEE, Piscataway, NJ, USA, IEEE International Conference on Robotics and Automation (ICRA), May 2017 (inproceedings)

Abstract
Magnetic untethered millirobots, which are actuated and controlled by remote magnetic fields, have been proposed for medical applications due to their ability to safely pass through tissues at long ranges. For example, magnetic resonance imaging (MRI) systems with a 3-7 T constant unidirectional magnetic field and 3D gradient coils have been used to actuate magnetic robots. Such magnetically constrained systems place limits on the degrees of freedom that can be actuated for untethered devices. This paper presents a design and actuation methodology for a magnetic millirobot that exhibits both position and orientation control in 2D under a magnetic field, dominated by a constant unidirectional magnetic field as found in MRI systems. Placing a spherical permanent magnet, which is free to rotate inside the millirobot and located away from the center of mass, allows the generation of net forces and torques with applied 3D magnetic field gradients. We model this system in a 3D planar case and experimentally demonstrate open-loop control of both position and orientation by the applied 2D field gradients. The actuation performance is characterized across the most important design variables, and we experimentally demonstrate that the proposed approach is feasible.

DOI [BibTex]

DOI [BibTex]


Magnetically actuated soft capsule endoscope for fine-needle aspiration biopsy
Magnetically actuated soft capsule endoscope for fine-needle aspiration biopsy

Son, D., Dogan, M. D., Sitti, M.

In Proceedings 2017 IEEE International Conference on Robotics and Automation (ICRA), pages: 1132-1139, IEEE, Piscataway, NJ, USA, 2017 IEEE International Conference on Robotics and Automation (ICRA), May 2017 (inproceedings)

Abstract
This paper presents a magnetically actuated soft capsule endoscope for fine-needle aspiration biopsy (B-MASCE) in the upper gastrointestinal tract. A thin and hollow needle is attached to the capsule, which can penetrate deeply into tissues to obtain subsurface biopsy sample. The design utilizes a soft elastomer body as a compliant mechanism to guide the needle. An internal permanent magnet provides a means for both actuation and tracking. The capsule is designed to roll towards its target and then deploy the biopsy needle in a precise location selected as the target area. B-MASCE is controlled by multiple custom-designed electromagnets while its position and orientation are tracked by a magnetic sensor array. In in vitro trials, B-MASCE demonstrated rolling locomotion and biopsy of a swine tissue model positioned inside an anatomical human stomach model. It was confirmed after the experiment that a tissue sample was retained inside the needle.

DOI Project Page [BibTex]

DOI Project Page [BibTex]


Planning spin-walking locomotion for automatic grasping of microobjects by an untethered magnetic microgripper
Planning spin-walking locomotion for automatic grasping of microobjects by an untethered magnetic microgripper

Dong, X., Sitti, M.

In 2017 IEEE International Conference on Robotics and Automation (ICRA), pages: 6612-6618, 2017 (inproceedings)

Abstract
Most demonstrated mobile microrobot tasks so far have been achieved via pick-and-placing and dynamic trapping with teleoperation or simple path following algorithms. In our previous work, an untethered magnetic microgripper has been developed which has advanced functions, such as gripping objects. Both teleoperated manipulation in 2D and 3D have been demonstrated. However, it is challenging to control the magnetic microgripper to carry out manipulation tasks, because the grasping of objects so far in the literature relies heavily on teleoperation, which takes several minutes with even a skilled human expert. Here, we propose a new spin-walking locomotion and an automated 2D grasping motion planner for the microgripper, which enables time-efficient automatic grasping of microobjects that has not been achieved yet for untethered microrobots. In its locomotion, the microgripper repeatedly rotates about two principal axes to regulate its pose and move precisely on a surface. The motion planner could plan different motion primitives for grasping and compensate the uncertainties in the motion by learning the uncertainties and planning accordingly. We experimentally demonstrated that, using the proposed method, the microgripper could align to the target pose with error less than 0.1 body length and grip the objects within 40 seconds. Our method could significantly improve the time efficiency of micro-scale manipulation and have potential applications in microassembly and biomedical engineering.

DOI Project Page [BibTex]

DOI Project Page [BibTex]


Methods, apparatuses, and systems for micromanipulation with adhesive fibrillar structures
Methods, apparatuses, and systems for micromanipulation with adhesive fibrillar structures

Sitti, M., Mengüç, Y.

US Patent 9,731,422, 2017 (patent)

Abstract
The present invention are methods for fabrication of micro- and/or nano-scale adhesive fibers and their use for movement and manipulation of objects. Further disclosed is a method of manipulating a part by providing a manipulation device with a plurality of fibers, where each fiber has a tip with a flat surface that is parallel to a backing layer, contacting the flat surfaces on an object, moving the object to a new location, then disengaging the tips from the object.

link (url) [BibTex]