Publications | Max Planck Institute for Intelligent Systems

X-ray Optics Fabrication Using Unorthodox Approaches

Sanli, U., Baluktsian, M., Ceylan, H., Sitti, M., Weigand, M., Schütz, G., Keskinbora, K.

Bulletin of the American Physical Society, APS, 2019 (article)

mms pi

mms pi Sanli, U., Baluktsian, M., Ceylan, H., Sitti, M., Weigand, M., Schütz, G., Keskinbora, K. X-ray Optics Fabrication Using Unorthodox Approaches Bulletin of the American Physical Society, APS, 2019 (article)

Temperature Gradients Drive Bulk Flow Within Microchannel Lined by Fluid–Fluid Interfaces

Amador, G. J., Ren, Z., Tabak, A. F., Alapan, Y., Yasa, O., Sitti, M.

Small, 15, Wiley Online Library, 2019 (article)

pi Amador, G. J., Ren, Z., Tabak, A. F., Alapan, Y., Yasa, O., Sitti, M. Temperature Gradients Drive Bulk Flow Within Microchannel Lined by Fluid–Fluid Interfaces Small, 15, Wiley Online Library, 2019 (article)

Microrobotics and Microorganisms: Biohybrid Autonomous Cellular Robots

Alapan, Y., Yasa, O., Yigit, B., Yasa, I. C., Erkoc, P., Sitti, M.

Annual Review of Control, Robotics, and Autonomous Systems, 2019 (article)

pi Alapan, Y., Yasa, O., Yigit, B., Yasa, I. C., Erkoc, P., Sitti, M. Microrobotics and Microorganisms: Biohybrid Autonomous Cellular Robots Annual Review of Control, Robotics, and Autonomous Systems, 2019 (article)

Woodward, M. A., Sitti, M.

Tailored Magnetic Springs for Shape-Memory Alloy Actuated Mechanisms in Miniature Robots

IEEE Transactions on Robotics, 35, 2019 (article)

Abstract

Animals can incorporate large numbers of actuators because of the characteristics of muscles; whereas, robots cannot, as typical motors tend to be large, heavy, and inefficient. However, shape-memory alloys (SMA), materials that contract during heating because of change in their crystal structure, provide another option. SMA, though, is unidirectional and therefore requires an additional force to reset (extend) the actuator, which is typically provided by springs or antagonistic actuation. These strategies, however, tend to limit the actuator's work output and functionality as their force-displacement relationships typically produce increasing resistive force with limited variability. In contrast, magnetic springs-composed of permanent magnets, where the interaction force between magnets mimics a spring force-have much more variable force-displacement relationships and scale well with SMA. However, as of yet, no method for designing magnetic springs for SMA-actuators has been demonstrated. Therefore, in this paper, we present a new methodology to tailor magnetic springs to the characteristics of these actuators, with experimental results both for the device and robot-integrated SMA-actuators. We found magnetic building blocks, based on sets of permanent magnets, which are well-suited to SMAs and have the potential to incorporate features such as holding force, state transitioning, friction minimization, auto-alignment, and self-mounting. We show magnetic springs that vary by more than 3 N in 750 $\mu$m and two SMA-actuated devices that allow the MultiMo-Bat to reach heights of up to 4.5 m without, and 3.6 m with, integrated gliding airfoils. Our results demonstrate the potential of this methodology to add previously impossible functionality to smart material actuators. We anticipate this methodology will inspire broader consideration of the use of magnetic springs in miniature robots and further study of the potential of tailored magnetic springs throughout mechanical systems.

pi Woodward, M. A., Sitti, M. Tailored Magnetic Springs for Shape-Memory Alloy Actuated Mechanisms in Miniature Robots IEEE Transactions on Robotics, 35, 2019 (article)

Magnetically Actuated Soft Capsule Endoscope for Fine-Needle Biopsy

Son, D., Gilbert, H., Sitti, M.

Soft robotics, Mary Ann Liebert, Inc., publishers 140 Huguenot Street, 3rd Floor New …, 2019 (article)

pi Son, D., Gilbert, H., Sitti, M. Magnetically Actuated Soft Capsule Endoscope for Fine-Needle Biopsy Soft robotics, Mary Ann Liebert, Inc., publishers 140 Huguenot Street, 3rd Floor New …, 2019 (article)

Thrust and Hydrodynamic Efficiency of the Bundled Flagella

Danis, U., Rasooli, R., Chen, C., Dur, O., Sitti, M., Pekkan, K.

Micromachines, 10, 2019 (article)

pi Danis, U., Rasooli, R., Chen, C., Dur, O., Sitti, M., Pekkan, K. Thrust and Hydrodynamic Efficiency of the Bundled Flagella Micromachines, 10, 2019 (article)

3D-Printed Biodegradable Microswimmer for Theranostic Cargo Delivery and Release

Ceylan, H., Yasa, I. C., Yasa, O., Tabak, A. F., Giltinan, J., Sitti, M.

ACS Nano, ACS Publications, 2019 (article)

pi Ceylan, H., Yasa, I. C., Yasa, O., Tabak, A. F., Giltinan, J., Sitti, M. 3D-Printed Biodegradable Microswimmer for Theranostic Cargo Delivery and Release ACS Nano, ACS Publications, 2019 (article)

The near and far of a pair of magnetic capillary disks

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

Soft Matter, 2019 (article)

pi Koens, L., Wang, W., Sitti, M., Lauga, E. The near and far of a pair of magnetic capillary disks Soft Matter, 2019 (article)

Multifarious Transit Gates for Programmable Delivery of Bio‐functionalized Matters

Hu, X., Torati, S. R., Kim, H., Yoon, J., Lim, B., Kim, K., Sitti, M., Kim, C.

Small, Wiley Online Library, 2019 (article)

pi Hu, X., Torati, S. R., Kim, H., Yoon, J., Lim, B., Kim, K., Sitti, M., Kim, C. Multifarious Transit Gates for Programmable Delivery of Bio‐functionalized Matters Small, Wiley Online Library, 2019 (article)

Precise Control of Lyotropic Chromonic Liquid Crystals Alignment through Surface Topography

Guo, Y., Shahsavan, H., Davidson, Z., Sitti, M.

ACS applied materials \& interfaces, ACS Publications, 2019 (article)

pi Guo, Y., Shahsavan, H., Davidson, Z., Sitti, M. Precise Control of Lyotropic Chromonic Liquid Crystals Alignment through Surface Topography ACS applied materials \& interfaces, ACS Publications, 2019 (article)

Multi-functional soft-bodied jellyfish-like swimming

Ren, Z., Hu, W., Dong, X., Sitti, M.

Nature communications, 10, 2019 (article)

pi Ren, Z., Hu, W., Dong, X., Sitti, M. Multi-functional soft-bodied jellyfish-like swimming Nature communications, 10, 2019 (article)

Welcome to Progress in Biomedical Engineering

Sitti, M.

Progress in Biomedical Engineering, 1, IOP Publishing, 2019 (article)

pi Sitti, M. Welcome to Progress in Biomedical Engineering Progress in Biomedical Engineering, 1, IOP Publishing, 2019 (article)

Mechanics of a pressure-controlled adhesive membrane for soft robotic gripping on curved surfaces

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

Extreme Mechanics Letters, Elsevier, 2019 (article)

pi Song, S., Drotlef, D., Paik, J., Majidi, C., Sitti, M. Mechanics of a pressure-controlled adhesive membrane for soft robotic gripping on curved surfaces Extreme Mechanics Letters, Elsevier, 2019 (article)

Graphene oxide synergistically enhances antibiotic efficacy in Vancomycin resistance Staphylococcus aureus

Singh, V., Kumar, V., Kashyap, S., Singh, A. V., Kishore, V., Sitti, M., Saxena, P. S., Srivastava, A.

ACS Applied Bio Materials, ACS Publications, 2019 (article)

pi Singh, V., Kumar, V., Kashyap, S., Singh, A. V., Kishore, V., Sitti, M., Saxena, P. S., Srivastava, A. Graphene oxide synergistically enhances antibiotic efficacy in Vancomycin resistance Staphylococcus aureus ACS Applied Bio Materials, ACS Publications, 2019 (article)

Review of emerging concepts in nanotoxicology: opportunities and challenges for safer nanomaterial design

Singh, A. V., Laux, P., Luch, A., Sudrik, C., Wiehr, S., Wild, A., Santamauro, G., Bill, J., Sitti, M.

Toxicology Mechanisms and Methods, 2019 (article)

pi Singh, A. V., Laux, P., Luch, A., Sudrik, C., Wiehr, S., Wild, A., Santamauro, G., Bill, J., Sitti, M. Review of emerging concepts in nanotoxicology: opportunities and challenges for safer nanomaterial design Toxicology Mechanisms and Methods, 2019 (article)

Hakan Ceylan, I. C. Y. U. K. W. H. M. S.

Translational prospects of untethered medical microrobots

Progress in Biomedical Engineering, 1, 2019 (article)

pi Hakan Ceylan, I. C. Y. U. K. W. H. M. S. Translational prospects of untethered medical microrobots Progress in Biomedical Engineering, 1, 2019 (article)

Multifunctional magnetic hairbot for untethered osteogenesis, ultrasound contrast imaging and drug delivery

Singh, A. V., Ansari, M. H. D., Dayan, C. B., Giltinan, J., Wang, S., Yu, Y., Kishore, V., Laux, P., Luch, A., Sitti, M.

Biomaterials, 219, Elsevier, 2019 (article)

pi Singh, A. V., Ansari, M. H. D., Dayan, C. B., Giltinan, J., Wang, S., Yu, Y., Kishore, V., Laux, P., Luch, A., Sitti, M. Multifunctional magnetic hairbot for untethered osteogenesis, ultrasound contrast imaging and drug delivery Biomaterials, 219, Elsevier, 2019 (article)

Pena-Francesch, A., Giltinan, J., Sitti, M.

Multifunctional and biodegradable self-propelled protein motors

Nature communications, 10, Nature Publishing Group, 2019 (article)

pi Pena-Francesch, A., Giltinan, J., Sitti, M. Multifunctional and biodegradable self-propelled protein motors Nature communications, 10, Nature Publishing Group, 2019 (article)

Cohesive self-organization of mobile microrobotic swarms

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

arXiv preprint arXiv:1907.05856, 2019 (article)

pi Yigit, B., Alapan, Y., Sitti, M. Cohesive self-organization of mobile microrobotic swarms arXiv preprint arXiv:1907.05856, 2019 (article)

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Automated Generation of Reactive Programs from Human Demonstration for Orchestration of Robot Behaviors

Berenz, V., Bjelic, A., Mainprice, J.

ArXiv, 2019 (article)

Abstract

Social robots or collaborative robots that have to interact with people in a reactive way are difficult to program. This difficulty stems from the different skills required by the programmer: to provide an engaging user experience the behavior must include a sense of aesthetics while robustly operating in a continuously changing environment. The Playful framework allows composing such dynamic behaviors using a basic set of action and perception primitives. Within this framework, a behavior is encoded as a list of declarative statements corresponding to high-level sensory-motor couplings. To facilitate non-expert users to program such behaviors, we propose a Learning from Demonstration (LfD) technique that maps motion capture of humans directly to a Playful script. The approach proceeds by identifying the sensory-motor couplings that are active at each step using the Viterbi path in a Hidden Markov Model (HMM). Given these activation patterns, binary classifiers called evaluations are trained to associate activations to sensory data. Modularity is increased by clustering the sensory-motor couplings, leading to a hierarchical tree structure. The novelty of the proposed approach is that the learned behavior is encoded not in terms of trajectories in a task space, but as couplings between sensory information and high-level motor actions. This provides advantages in terms of behavioral generalization and reactivity displayed by the robot.

am Berenz, V., Bjelic, A., Mainprice, J. Automated Generation of Reactive Programs from Human Demonstration for Orchestration of Robot Behaviors ArXiv, 2019 (article)

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Mobile microrobots for active therapeutic delivery

Erkoc, P., Yasa, I. C., Ceylan, H., Yasa, O., Alapan, Y., Sitti, M.

Advanced Therapeutics, Wiley Online Library, 2019 (article)

pi Erkoc, P., Yasa, I. C., Ceylan, H., Yasa, O., Alapan, Y., Sitti, M. Mobile microrobots for active therapeutic delivery Advanced Therapeutics, Wiley Online Library, 2019 (article)

Shape-encoded dynamic assembly of mobile micromachines

Alapan, Y., Yigit, B., Beker, O., Demirörs, A. F., Sitti, M.

Nature, 18, 2019 (article)

pi Alapan, Y., Yigit, B., Beker, O., Demirörs, A. F., Sitti, M. Shape-encoded dynamic assembly of mobile micromachines Nature, 18, 2019 (article)

Microfluidics Integrated Lithography‐Free Nanophotonic Biosensor for the Detection of Small Molecules

Sreekanth, K. V., Sreejith, S., Alapan, Y., Sitti, M., Lim, C. T., Singh, R.

Advanced Optical Materials, 2019 (article)

pi Sreekanth, K. V., Sreejith, S., Alapan, Y., Sitti, M., Lim, C. T., Singh, R. Microfluidics Integrated Lithography‐Free Nanophotonic Biosensor for the Detection of Small Molecules Advanced Optical Materials, 2019 (article)

ENGINEERING Bio-inspired robotic collectives

Sitti, M.

Nature, 567, pages: 314-315, Macmillan Publishers Ltd., London, England, 2019 (article)

pi Sitti, M. ENGINEERING Bio-inspired robotic collectives Nature, 567, pages: 314-315, Macmillan Publishers Ltd., London, England, 2019 (article)

Immihan Ceren Yasa, A. F. T. O. Y. H. C. M. S.

3D‐Printed Microrobotic Transporters with Recapitulated Stem Cell Niche for Programmable and Active Cell Delivery

Advanced Functional Materials , 29, 2019 (article)

pi Immihan Ceren Yasa, A. F. T. O. Y. H. C. M. S. 3D‐Printed Microrobotic Transporters with Recapitulated Stem Cell Niche for Programmable and Active Cell Delivery Advanced Functional Materials , 29, 2019 (article)

Peptide-Induced Biomineralization of Tin Oxide (SnO2) Nanoparticles for Antibacterial Applications

Singh, A. V., Jahnke, T., Xiao, Y., Wang, S., Yu, Y., David, H., Richter, G., Laux, P., Luch, A., Srivastava, A., Saxena, P. S., Bill, J., Sitti, M.

Journal of nanoscience and nanotechnology, 19, American Scientific Publishers, 2019 (article)

pi Singh, A. V., Jahnke, T., Xiao, Y., Wang, S., Yu, Y., David, H., Richter, G., Laux, P., Luch, A., Srivastava, A., Saxena, P. S., Bill, J., Sitti, M. Peptide-Induced Biomineralization of Tin Oxide (SnO2) Nanoparticles for Antibacterial Applications Journal of nanoscience and nanotechnology, 19, American Scientific Publishers, 2019 (article)

Electromechanical actuation of dielectric liquid crystal elastomers for soft robotics

Davidson, Z., Shahsavan, H., Guo, Y., Hines, L., Xia, Y., Yang, S., Sitti, M.

Bulletin of the American Physical Society, APS, 2019 (article)

pi Davidson, Z., Shahsavan, H., Guo, Y., Hines, L., Xia, Y., Yang, S., Sitti, M. Electromechanical actuation of dielectric liquid crystal elastomers for soft robotics Bulletin of the American Physical Society, APS, 2019 (article)

Simultaneous Six-Degree-of-Freedom Control of a Single-Body Magnetic Microrobot

Giltinan, J., Sitti, M.

IEEE Robotics and Automation Letters, 4, 2019 (article)

pi Giltinan, J., Sitti, M. Simultaneous Six-Degree-of-Freedom Control of a Single-Body Magnetic Microrobot IEEE Robotics and Automation Letters, 4, 2019 (article)

Monolithic shape-programmable dielectric liquid crystal elastomer actuators

Davidson, Z. S., Shahsavan, H., Aghakhani, A., Guo, Y., Hines, L., Xia, Y., Yang, S., Sitti, M.

arXiv preprint arXiv:1904.09606, 2019 (article)

pi Davidson, Z. S., Shahsavan, H., Aghakhani, A., Guo, Y., Hines, L., Xia, Y., Yang, S., Sitti, M. Monolithic shape-programmable dielectric liquid crystal elastomer actuators arXiv preprint arXiv:1904.09606, 2019 (article)

Bio-inspired composite microfibers for strong and reversible adhesion on smooth surfaces

Drotlef, D., Dayan, C., Sitti, M.

Integrative and comparative biology, 2019 (article)

pi Drotlef, D., Dayan, C., Sitti, M. Bio-inspired composite microfibers for strong and reversible adhesion on smooth surfaces Integrative and comparative biology, 2019 (article)

Elevation and Azimuth Rotational Actuation of an Untethered Millirobot by MRI Gradient Coils

Erin, O., Gilbert, H. B., Tabak, A. F., Sitti, M.

IEEE Transactions on Robotics, IEEE, 2019 (article)

pi Erin, O., Gilbert, H. B., Tabak, A. F., Sitti, M. Elevation and Azimuth Rotational Actuation of an Untethered Millirobot by MRI Gradient Coils IEEE Transactions on Robotics, IEEE, 2019 (article)

Learning to Navigate Endoscopic Capsule Robots

Turan, M., Almalioglu, Y., Gilbert, H. B., Mahmood, F., Durr, N. J., Araujo, H., Sarı, A. E., Ajay, A., Sitti, M.

IEEE Robotics and Automation Letters, 4, 2019 (article)

pi Turan, M., Almalioglu, Y., Gilbert, H. B., Mahmood, F., Durr, N. J., Araujo, H., Sarı, A. E., Ajay, A., Sitti, M. Learning to Navigate Endoscopic Capsule Robots IEEE Robotics and Automation Letters, 4, 2019 (article)

2016

A New Perspective and Extension of the Gaussian Filter

Wüthrich, M., Trimpe, S., Garcia Cifuentes, C., Kappler, D., Schaal, S.

The International Journal of Robotics Research, 35(14):1731-1749, December 2016 (article)

Abstract

The Gaussian Filter (GF) is one of the most widely used filtering algorithms; instances are the Extended Kalman Filter, the Unscented Kalman Filter and the Divided Difference Filter. The GF represents the belief of the current state by a Gaussian distribution, whose mean is an affine function of the measurement. We show that this representation can be too restrictive to accurately capture the dependences in systems with nonlinear observation models, and we investigate how the GF can be generalized to alleviate this problem. To this end, we view the GF as the solution to a constrained optimization problem. From this new perspective, the GF is seen as a special case of a much broader class of filters, obtained by relaxing the constraint on the form of the approximate posterior. On this basis, we outline some conditions which potential generalizations have to satisfy in order to maintain the computational efficiency of the GF. We propose one concrete generalization which corresponds to the standard GF using a pseudo measurement instead of the actual measurement. Extending an existing GF implementation in this manner is trivial. Nevertheless, we show that this small change can have a major impact on the estimation accuracy.

am ics

PDF DOI Project Page [BibTex]

2016

am ics Wüthrich, M., Trimpe, S., Garcia Cifuentes, C., Kappler, D., Schaal, S. A New Perspective and Extension of the Gaussian Filter The International Journal of Robotics Research, 35(14):1731-1749, December 2016 (article)

PDF DOI Project Page [BibTex]

Bioengineered and biohybrid bacteria-based systems for drug delivery

Hosseinidoust, Z., Mostaghaci, B., Yasa, O., Park, B., Singh, A. V., Sitti, M.

Advanced Drug Delivery Reviews, 106, pages: 27-44, Elsevier, November 2016 (article)

Abstract

The use of bacterial cells as agents of medical therapy has a long history. Research that was ignited over a century ago with the accidental infection of cancer patients has matured into a platform technology that offers the promise of opening up new potential frontiers in medical treatment. Bacterial cells exhibit unique characteristics that make them well-suited as smart drug delivery agents. Our ability to genetically manipulate the molecular machinery of these cells enables the customization of their therapeutic action as well as its precise tuning and spatio-temporal control, allowing for the design of unique, complex therapeutic functions, unmatched by current drug delivery systems. Early results have been promising, but there are still many important challenges that must be addressed. We present a review of promises and challenges of employing bioengineered bacteria in drug delivery systems and introduce the biohybrid design concept as a new additional paradigm in bacteria-based drug delivery.

pi Hosseinidoust, Z., Mostaghaci, B., Yasa, O., Park, B., Singh, A. V., Sitti, M. Bioengineered and biohybrid bacteria-based systems for drug delivery Advanced Drug Delivery Reviews, 106, pages: 27-44, Elsevier, November 2016 (article)

A 5-D localization method for a magnetically manipulated untethered robot using a 2-D array of Hall-effect sensors

Son, D., Yim, S., Sitti, M.

IEEE/ASME Transactions on Mechatronics, 21(2):708-716, IEEE, October 2016 (article)

Abstract

This paper introduces a new five-dimensional localization method for an untethered meso-scale magnetic robot, which is manipulated by a computer-controlled electromagnetic system. The developed magnetic localization setup is a two-dimensional array of mono-axial Hall-effect sensors, which measure the perpendicular magnetic fields at their given positions. We introduce two steps for localizing a magnetic robot more accurately. First, the dipole modeled magnetic field of the electromagnet is subtracted from the measured data in order to determine the robot's magnetic field. Secondly, the subtracted magnetic field is twice differentiated in the perpendicular direction of the array, so that the effect of the electromagnetic field in the localization process is minimized. Five variables regarding the position and orientation of the robot are determined by minimizing the error between the measured magnetic field and the modeled magnetic field in an optimization method. The resulting position error is 2.1±0.8 mm and angular error is 6.7±4.3° within the applicable range (5 cm) of magnetic field sensors at 200 Hz. The proposed localization method would be used for the position feedback control of untethered magnetic devices or robots for medical applications in the future.

pi Son, D., Yim, S., Sitti, M. A 5-D localization method for a magnetically manipulated untethered robot using a 2-D array of Hall-effect sensors IEEE/ASME Transactions on Mechatronics, 21(2):708-716, IEEE, October 2016 (article)

DOI Project Page Project Page [BibTex]

High-Performance Multiresponsive Paper Actuators

Amjadi, M., Sitti, M.

ACS Nano, 10(11):10202-10210, American Chemical Society, October 2016 (article)

Abstract

There is an increasing demand for soft actuators because of their importance in soft robotics, artificial muscles, biomimetic devices, and beyond. However, the development of soft actuators capable of low-voltage operation, powerful actuation, and programmable shape-changing is still challenging. In this work, we propose programmable bilayer actuators that operate based on the large hygroscopic contraction of the copy paper and simultaneously large thermal expansion of the polypropylene film upon increasing the temperature. The electrothermally activated bending actuators can function with low voltages (≤ 8 V), low input electric power per area (P ≤ 0.14 W cm–2), and low temperature changes (≤ 35 °C). They exhibit reversible shape-changing behavior with curvature radii up to 1.07 cm–1 and bending angle of 360°, accompanied by powerful actuation. Besides the electrical activation, they can be powered by humidity or light irradiation. We finally demonstrate the use of our paper actuators as a soft gripper robot and a lightweight paper wing for aerial robotics.

pi Amjadi, M., Sitti, M. High-Performance Multiresponsive Paper Actuators ACS Nano, 10(11):10202-10210, American Chemical Society, October 2016 (article)

DOI Project Page Project Page [BibTex]

Programmable assembly of heterogeneous microparts by an untethered mobile capillary microgripper

Giltinan, J., Diller, E., Sitti, M.

Lab on a Chip, 16(22):4445-4457, Royal Society of Chemistry, October 2016 (article)

Abstract

At the sub-millimeter scale, capillary forces enable robust and reversible adhesion between biological organisms and varied substrates. Current human-engineered mobile untethered micromanipulation systems rely on forces which scale poorly or utilize gripper-part designs that promote manipulation. Capillary forces, alternatively, are dependent upon the surface chemistry (which is scale independent) and contact perimeter, which conforms to the part surface. We report a mobile capillary microgripper that is able to pick and place parts of various materials and geometries, and is thus ideal for microassembly tasks that cannot be accomplished by large tethered manipulators. We achieve the programmable assembly of sub-millimeter parts in an enclosed three-dimensional aqueous environment by creating a capillary bridge between the targeted part and a synthetic, untethered, mobile body. The parts include both hydrophilic and hydrophobic components: hydrogel, kapton, human hair, and biological tissue. The 200 μm untethered system can be controlled with five-degrees-of-freedom and advances progress towards autonomous desktop manufacturing for tissue engineering, complex micromachines, microfluidic devices, and meta-materials.

pi Giltinan, J., Diller, E., Sitti, M. Programmable assembly of heterogeneous microparts by an untethered mobile capillary microgripper Lab on a Chip, 16(22):4445-4457, Royal Society of Chemistry, October 2016 (article)

Composition-dependent underwater adhesion of catechol-bearing hydrogels

Wu, H., Sariola, V., Zhao, J., Ding, H., Sitti, M., Bettinger, C. J.

Polymer International, 65(11):1355-1359, John Wiley & Sons, Ltd, September 2016 (article)

Abstract

Interfacial adhesion-mediated transfer printing processes can integrate functional electronic microstructures with polymeric substrates that are bendable and stretchable. Transfer printing has also been extended to catechol-bearing adhesive hydrogels. This study presents indentation adhesion tests between catechol-bearing hydrogel substrates with catechol concentrations varying from 0 to 10% (mol/mol) and thin-film materials commonly used in microelectronic fabrication including polymers, noble metals and oxides. The results indicate that the interfacial adhesion of catechol-bearing hydrogels is positively correlated with the concentration of catechol-bearing monomers as well as the retraction velocity during transfer printing. This study can inform transfer printing processes for microfabricated structures to compliant hydrated substrates such as hygroscopic monomers, mesoporous polymer networks and hydrogels. © 2016 Society of Chemical Industry

pi Wu, H., Sariola, V., Zhao, J., Ding, H., Sitti, M., Bettinger, C. J. Composition-dependent underwater adhesion of catechol-bearing hydrogels Polymer International, 65(11):1355-1359, John Wiley & Sons, Ltd, September 2016 (article)

Bacteria-Driven Particles: Patterned and Specific Attachment of Bacteria on Biohybrid Bacteria-Driven Microswimmers (Adv. Healthcare Mater. 18/2016)

Singh, A. V., Sitti, M.

Advanced Healthcare Materials, 5(18):2306-2306, September 2016 (article)

Abstract

On page 2325, Ajay Vikram Singh and Metin Sitti propose a facile surface patterning technique and a specific, strong biotin–streptavidin bonding of bacteria on patterned surfaces to fabricate Janus particles that are propelled by the attached bacteria. Such bacteria-driven Janus microswimmers could be used for future medicine in targeted drug delivery and environmental remediation.

pi Singh, A. V., Sitti, M. Bacteria-Driven Particles: Patterned and Specific Attachment of Bacteria on Biohybrid Bacteria-Driven Microswimmers (Adv. Healthcare Mater. 18/2016) Advanced Healthcare Materials, 5(18):2306-2306, September 2016 (article)

The effect of temperature and humidity on adhesion of a gecko-inspired adhesive: implications for the natural system

Stark, A. Y., Klittich, M. R., Sitti, M., Niewiarowski, P. H., Dhinojwala, A.

Scientific Reports, 6, pages: 30936, Nature Publishing Group, August 2016 (article)

Abstract

The adhesive system of geckos has inspired hundreds of synthetic adhesives. While this system has been used relentlessly as a source of inspiration, less work has been done in reverse, where synthetics are used to test questions and hypotheses about the natural system. Here we take such an approach. We tested shear adhesion of a mushroom-tipped synthetic gecko adhesive under conditions that produced perplexing results in the natural adhesive system. Synthetic samples were tested at two temperatures (12 °C and 32 °C) and four different humidity levels (30%, 55%, 70%, and 80% RH). Surprisingly, adhesive performance of the synthetic samples matched that of living geckos, suggesting that uncontrolled parameters in the natural system, such as surface chemistry and material changes, may not be as influential in whole-animal performance as previously thought. There was one difference, however, when comparing natural and synthetic adhesive performance. At 12 °C and 80% RH, adhesion of the synthetic structures was lower than expected based on the natural system’s performance. Our approach highlights a unique opportunity for both biologists and material scientists, where new questions and hypotheses can be fueled by joint comparisons of the natural and synthetic systems, ultimately improving knowledge of both.

pi Stark, A. Y., Klittich, M. R., Sitti, M., Niewiarowski, P. H., Dhinojwala, A. The effect of temperature and humidity on adhesion of a gecko-inspired adhesive: implications for the natural system Scientific Reports, 6, pages: 30936, Nature Publishing Group, August 2016 (article)

DOOMED: Direct Online Optimization of Modeling Errors in Dynamics

Ratliff, N., Meier, F., Kappler, D., Schaal, S.

arXiv preprint arXiv:1608.00309, August 2016 (article)

am Ratliff, N., Meier, F., Kappler, D., Schaal, S. DOOMED: Direct Online Optimization of Modeling Errors in Dynamics arXiv preprint arXiv:1608.00309, August 2016 (article)

Magnetic propulsion of robotic sperms at low-Reynolds number

Khalil, I. S., Fatih Tabak, A., Klingner, A., Sitti, M.

Applied Physics Letters, 109(3):033701, AIP Publishing, July 2016 (article)

Abstract

We investigate the microswimming behaviour of robotic sperms in viscous fluids. These robotic sperms are fabricated from polystyrene dissolved in dimethyl formamide and iron-oxide nanoparticles. This composition allows the nanoparticles to be concentrated within the bead of the robotic sperm and provide magnetic dipole, whereas the flexibility of the ultra-thin tail enables flagellated locomotion using magnetic fields in millitesla range. We show that these robotic sperms have similar morphology and swimming behaviour to those of sperm cells. Moreover, we show experimentally that our robotic sperms swim controllably at an average speed of approximately one body length per second (around 125 μm s−1), and they are relatively faster than the microswimmers that depend on planar wave propulsion in low-Reynolds number fluids.

pi Khalil, I. S., Fatih Tabak, A., Klingner, A., Sitti, M. Magnetic propulsion of robotic sperms at low-Reynolds number Applied Physics Letters, 109(3):033701, AIP Publishing, July 2016 (article)

Six-degree-of-freedom magnetic actuation for wireless microrobotics

Diller, E., Giltinan, J., Lum, G. Z., Ye, Z., Sitti, M.

The International Journal of Robotics Research, 35(1-3):114-128, SAGE Publications Sage UK: London, England, June 2016 (article)

Abstract

Existing remotely actuated magnetic microrobots exhibit a maximum of only five-degree-of-freedom (DOF) actuation, as creation of a driving torque about the microrobot magnetization axis is not achievable. This lack of full orientation control limits the effectiveness of existing microrobots for precision tasks of object manipulation and orientation for advanced medical, biological and micromanufacturing applications. This paper presents a magnetic actuation method that allows remotely powered microrobots to achieve full six-DOF actuation by considering the case of a non-uniform magnetization profile within the microrobot body. This non-uniform magnetization allows for additional rigid-body torques to be induced from magnetic forces via a moment arm. A general analytical model presents the working principle for continuous and discrete magnetization profiles, which is applied to permanent or non-permanent (soft) magnet bodies. Several discrete-magnetization designs are also presented which possess reduced coupling between magnetic forces and induced rigid-body torques. Design guidelines are introduced which can be followed to ensure that a magnetic microrobot design is capable of six-DOF actuation. A simple permanent-magnet prototype is fabricated and used to quantitatively demonstrate the accuracy of the analytical model in a constrained-DOF environment and qualitatively for free motion in a viscous liquid three-dimensional environment. Results show that desired forces and torques can be created with high precision and limited parasitic actuation, allowing for full six-DOF actuation using limited feedback control

pi Diller, E., Giltinan, J., Lum, G. Z., Ye, Z., Sitti, M. Six-degree-of-freedom magnetic actuation for wireless microrobotics The International Journal of Robotics Research, 35(1-3):114-128, SAGE Publications Sage UK: London, England, June 2016 (article)

System and method to magnetically actuate a capsule endoscopic robot for diagnosis and treatment

Sitti, M., Yim, S.

May 2016, US Patent 9,445,711 (patent)

Abstract

Present invention describes a swallowable device with a soft, compliant exterior, whose shape can be changed through the use of magnetic fields, and which can be locomoted in a rolling motion through magnetic control from the exterior of the patient. The present invention could be used for a variety of medical applications inside the GI tract including but not limited to drug delivery, biopsy, heat cauterization, pH sensing, biochemical sensing, micro-surgery, and active imaging.

link (url) [BibTex]

pi Sitti, M., Yim, S. System and method to magnetically actuate a capsule endoscopic robot for diagnosis and treatment May 2016, US Patent 9,445,711 (patent)

link (url) [BibTex]

Gallium Adhesion: Phase Change of Gallium Enables Highly Reversible and Switchable Adhesion (Adv. Mater. 25/2016)

Ye, Z., Lum, G. Z., Song, S., Rich, S., Sitti, M.

Advanced Materials, 28(25):5087-5087, May 2016 (article)

Abstract

Gallium exhibits highly reversible and switchable adhesion when it undergoes a solid–liquid phase transition. The robustness of gallium is notable as it exhibits strong performance on a wide range of smooth and rough surfaces, under both dry and wet conditions. Gallium may therefore find numerous applications in transfer printing, robotics, electronic packaging, and biomedicine.

pi Ye, Z., Lum, G. Z., Song, S., Rich, S., Sitti, M. Gallium Adhesion: Phase Change of Gallium Enables Highly Reversible and Switchable Adhesion (Adv. Mater. 25/2016) Advanced Materials, 28(25):5087-5087, May 2016 (article)

Patterned and Specific Attachment of Bacteria on Biohybrid Bacteria-Driven Microswimmers

Singh, A. V., Sitti, M.

Advanced Healthcare Materials, 5(18):2325-2331, May 2016 (article)

Abstract

A surface patterning technique and a specific and strong biotin–streptavidin bonding of bacteria on patterned surfaces are proposed to fabricate Janus particles that are propelled by the attached bacteria. Bacteria-driven Janus microswimmers with diameters larger than 3 μm show enhanced mean propulsion speed. Such microswimmers could be used for future applications such as targeted drug delivery and environmental remediation.

pi Singh, A. V., Sitti, M. Patterned and Specific Attachment of Bacteria on Biohybrid Bacteria-Driven Microswimmers Advanced Healthcare Materials, 5(18):2325-2331, May 2016 (article)

Shape-programmable magnetic soft matter

Lum, G. Z., Ye, Z., Dong, X., Marvi, H., Erin, O., Hu, W., Sitti, M.

Proceedings of the National Academy of Sciences, 113(41):E6007–E6015, National Acad Sciences, May 2016 (article)

Abstract

Shape-programmable matter is a class of active materials whose geometry can be controlled to potentially achieve mechanical functionalities beyond those of traditional machines. Among these materials, magnetically actuated matter is particularly promising for achieving complex time-varying shapes at small scale (overall dimensions smaller than 1 cm). However, previous work can only program these materials for limited applications, as they rely solely on human intuition to approximate the required magnetization profile and actuating magnetic fields for their materials. Here, we propose a universal programming methodology that can automatically generate the required magnetization profile and actuating fields for soft matter to achieve new time-varying shapes. The universality of the proposed method can therefore inspire a vast number of miniature soft devices that are critical in robotics, smart engineering surfaces and materials, and biomedical devices. Our proposed method includes theoretical formulations, computational strategies, and fabrication procedures for programming magnetic soft matter. The presented theory and computational method are universal for programming 2D or 3D time-varying shapes, whereas the fabrication technique is generic only for creating planar beams. Based on the proposed programming method, we created a jellyfish-like robot, a spermatozoid-like undulating swimmer, and an artificial cilium that could mimic the complex beating patterns of its biological counterpart.

pi Lum, G. Z., Ye, Z., Dong, X., Marvi, H., Erin, O., Hu, W., Sitti, M. Shape-programmable magnetic soft matter Proceedings of the National Academy of Sciences, 113(41):E6007–E6015, National Acad Sciences, May 2016 (article)

Inflated soft actuators with reversible stable deformations

Hines, L., Petersen, K., Sitti, M.

Advanced Materials, 28(19):3690-3696, March 2016 (article)

Abstract

Most soft robotic systems are currently dependent on bulky compressors or pumps. A soft actuation method is presented combining hyperelastic membranes and dielectric elastomer actuators to switch between stable deformations of sealed chambers. This method is capable of large repeatable deformations, and has a number of stable states proportional to the number of actuatable membranes in the chamber.

pi Hines, L., Petersen, K., Sitti, M. Inflated soft actuators with reversible stable deformations Advanced Materials, 28(19):3690-3696, March 2016 (article)

Chemotaxis of bio-hybrid multiple bacteria-driven microswimmers

Zhuang, J., Sitti, M.

Scientific reports, 6, pages: 32135, Nature Publishing Group, March 2016 (article)

Abstract

In this study, in a bio-hybrid microswimmer system driven by multiple Serratia marcescens bacteria, we quantify the chemotactic drift of a large number of microswimmers towards L-serine and elucidate the associated collective chemotaxis behavior by statistical analysis of over a thousand swimming trajectories of the microswimmers. The results show that the microswimmers have a strong heading preference for moving up the L-serine gradient, while their speed does not change considerably when moving up and down the gradient; therefore, the heading bias constitutes the major factor that produces the chemotactic drift. The heading direction of a microswimmer is found to be significantly more persistent when it moves up the L-serine gradient than when it travels down the gradient; this effect causes the apparent heading preference of the microswimmers and is the crucial reason that enables the seemingly cooperative chemotaxis of multiple bacteria on a microswimmer. In addition, we find that their chemotactic drift velocity increases superquadratically with their mean swimming speed, suggesting that chemotaxis of bio-hybrid microsystems can be enhanced by designing and building faster microswimmers. Such bio-hybrid microswimmers with chemotactic steering capability may find future applications in targeted drug delivery, bioengineering, and lab-on-a-chip devices.

pi Zhuang, J., Sitti, M. Chemotaxis of bio-hybrid multiple bacteria-driven microswimmers Scientific reports, 6, pages: 32135, Nature Publishing Group, March 2016 (article)