publications

2022

1. Nat. Comm.

   Reduced rotational flows enable the translation of surface-rolling microrobots in confined spaces

   Ugur Bozuyuk, Amirreza Aghakhani, Yunus Alapan, and 3 more authors

   Nature Communications 2022

   Bib HTML PDF

   @article{bozuyuk2022reduced,
     title = {Reduced rotational flows enable the translation of surface-rolling microrobots in confined spaces},
     author = {Bozuyuk, Ugur and Aghakhani, Amirreza and Alapan, Yunus and Yunusa, Muhammad and Wrede, Paul and Sitti, Metin},
     journal = {Nature Communications},
     volume = {13},
     number = {1},
     pages = {6289},
     year = {2022},
     doi = {https://doi.org/10.1038/s41467-022-34023-z},
     publisher = {Nature Publishing Group UK London},
   }

2. Sci. Adv.

   Real-time 3D optoacoustic tracking of cell-sized magnetic microrobots circulating in the mouse brain vasculature

   Paul Wrede, Oleksiy Degtyaruk, Sandeep Kumar Kalva, and 6 more authors

   Science Advances 2022

   Abs Bib HTML

   Mobile microrobots hold remarkable potential to revolutionize health care by enabling unprecedented active medical interventions and theranostics, such as active cargo delivery and microsurgical manipulations in hard-to-reach body sites. High-resolution imaging and control of cell-sized microrobots in the in vivo vascular system remains an unsolved challenge toward their clinical use. To overcome this limitation, we propose noninvasive real-time detection and tracking of circulating microrobots using optoacoustic imaging. We devised cell-sized nickel-based spherical Janus magnetic microrobots whose near-infrared optoacoustic signature is enhanced via gold conjugation. The 5-, 10-, and 20-μm-diameter microrobots are detected volumetrically both in bloodless ex vivo tissues and under real-life conditions with a strongly light-absorbing blood background. We further demonstrate real-time three-dimensional tracking and magnetic manipulation of the microrobots circulating in murine cerebral vasculature, thus paving the way toward effective and safe operation of cell-sized microrobots in challenging and clinically relevant intravascular environments. Cell-sized magnetic microrobots are tracked in the murine cerebral vasculature with noninvasive optoacoustic imaging.

   @article{wrede2022realtime,
     author = {Wrede, Paul and Degtyaruk, Oleksiy and Kalva, Sandeep Kumar and Deán-Ben, Xosé Luis and Bozuyuk, Ugur and Aghakhani, Amirreza and Akolpoglu, Birgul and Sitti, Metin and Razansky, Daniel},
     title = {Real-time 3D optoacoustic tracking of cell-sized magnetic microrobots circulating in the mouse brain vasculature},
     journal = {Science Advances},
     volume = {8},
     number = {19},
     pages = {eabm9132},
     year = {2022},
     doi = {10.1126/sciadv.abm9132},
   }

3. Sci. Adv.

   High shear rate propulsion of acoustic microrobots in complex biological fluids

   Amirreza Aghakhani, Abdon Pena-Francesch, Ugur Bozuyuk, and 3 more authors

   Science advances 2022

   Abs Bib HTML PDF

   Untethered microrobots offer a great promise for localized targeted therapy in hard-to-access spaces in our body. Despite recent advancements, most microrobot propulsion capabilities have been limited to homogenous Newtonian fluids. However, the biological fluids present in our body are heterogeneous and have shear rate–dependent rheological properties, which limit the propulsion of microrobots using conventional designs and actuation methods. We propose an acoustically powered microrobotic system, consisting of a three-dimensionally printed 30-micrometer-diameter hollow body with an oscillatory microbubble, to generate high shear rate fluidic flow for propulsion in complex biofluids. The acoustically induced microstreaming flow leads to distinct surface-slipping and puller-type propulsion modes in Newtonian and non-Newtonian fluids, respectively. We demonstrate efficient propulsion of the microrobots in diverse biological fluids, including in vitro navigation through mucus layers on biologically relevant three-dimensional surfaces. The microrobot design and high shear rate propulsion mechanism discussed herein could open new possibilities to deploy microrobots in complex biofluids toward minimally invasive targeted therapy.

   @article{aghakhani2022high,
     title = {High shear rate propulsion of acoustic microrobots in complex biological fluids},
     author = {Aghakhani, Amirreza and Pena-Francesch, Abdon and Bozuyuk, Ugur and Cetin, Hakan and Wrede, Paul and Sitti, Metin},
     journal = {Science advances},
     volume = {8},
     number = {10},
     pages = {eabm5126},
     year = {2022},
     publisher = {American Association for the Advancement of Science},
   }

4. Adv. Funct. Mater

   High-Performance Magnetic FePt (L10) Surface Microrollers Towards Medical Imaging-Guided Endovascular Delivery Applications

   Ugur Bozuyuk, Eylul Suadiye, Amirreza Aghakhani, and 8 more authors

   Advanced Functional Materials 2022

   Abs HTML

   Controlled microrobotic navigation in the vascular system can revolutionize minimally invasive medical applications, such as targeted drug and gene delivery. Magnetically controlled surface microrollers have emerged as a promising microrobotic platform for controlled navigation in the circulatory system. Locomotion of micrororollers in strong flow velocities is a highly challenging task, which requires magnetic materials having strong magnetic actuation properties while being biocompatible. The L10-FePt magnetic coating can achieve such requirements. Therefore, such coating has been integrated into 8 µm-diameter surface microrollers and investigated the medical potential of the system from magnetic locomotion performance, biocompatibility, and medical imaging perspectives. The FePt coating significantly advanced the magnetic performance and biocompatibility of the microrollers compared to a previously used magnetic material, nickel. The FePt coating also allowed multimodal imaging of microrollers in magnetic resonance and photoacoustic imaging in ex vivo settings without additional contrast agents. Finally, FePt-coated microrollers showed upstream locomotion ability against 4.5 cm s−1 average flow velocity with real-time photoacoustic imaging, demonstrating the navigation control potential of microrollers in the circulatory system for future in vivo applications. Overall, L10-FePt is conceived as the key material for image-guided propulsion in the vascular system to perform future targeted medical interventions.

2021

1. Nat. Rev. Mater.

   Soft Actuators for Real-World Applications

   Meng Li, Aniket Pal, Amirreza Aghakhani, and 2 more authors

   Nature Reviews Materials 2021

   Abs Bib HTML

   Inspired by physically adaptive, agile, reconfigurable and multifunctional soft-bodied animals and human muscles, soft actuators have been developed for a variety of applications, including soft grippers, artificial muscles, wearables, haptic devices and medical devices. However, the complex performance of biological systems cannot yet be fully replicated in synthetic designs. In this Review, we discuss new materials and structural designs for the engineering of soft actuators with physical intelligence and advanced properties, such as adaptability, multimodal locomotion, self-healing and multi-responsiveness. We examine how performance can be improved and multifunctionality implemented by using programmable soft materials, and highlight important real-world applications of soft actuators. Finally, we discuss the challenges and opportunities for next-generation soft actuators, including physical intelligence, adaptability, manufacturing scalability and reproducibility, extended lifetime and end-of-life strategies.

   @article{liSoftActuatorsRealworld2021,
     title = {Soft Actuators for Real-World Applications},
     author = {Li, Meng and Pal, Aniket and Aghakhani, Amirreza and {Pena-Francesch}, Abdon and Sitti, Metin},
     year = {2021},
     journal = {Nature Reviews Materials},
     pages = {1--15},
     publisher = {{Nature Publishing Group}},
   }

2. PNAS

   Shape Anisotropy-Governed Locomotion of Surface Microrollers on Vessel-like Microtopographies against Physiological Flows

   Ugur Bozuyuk, Yunus Alapan, Amirreza Aghakhani, and 2 more authors

   Proceedings of the National Academy of Sciences Mar 2021

   Abs Bib

   Surface microrollers are promising microrobotic systems for controlled navigation in the circulatory system thanks to their fast speeds and decreased flow velocities at the vessel walls. While surface propulsion on the vessel walls helps minimize the effect of strong fluidic forces, three-dimensional (3D) surface microtopography, comparable to the size scale of a microrobot, due to cellular morphology and organization emerges as a major challenge. Here, we show that microroller shape anisotropy determines the surface locomotion capability of microrollers on vessel-like 3D surface microtopographies against physiological flow conditions. The isotropic (single, 8.5 \textmu m diameter spherical particle) and anisotropic (doublet, two 4 \textmu m diameter spherical particle chain) magnetic microrollers generated similar translational velocities on flat surfaces, whereas the isotropic microrollers failed to translate on most of the 3D-printed vessel-like microtopographies. The computational fluid dynamics analyses revealed larger flow fields generated around isotropic microrollers causing larger resistive forces near the microtopographies, in comparison to anisotropic microrollers, and impairing their translation. The superior surface-rolling capability of the anisotropic doublet microrollers on microtopographical surfaces against the fluid flow was further validated in a vessel-on-a-chip system mimicking microvasculature. The findings reported here establish the design principles of surface microrollers for robust locomotion on vessel walls against physiological flows.

   @article{bozuyukShapeAnisotropygovernedLocomotion2021a,
     title = {Shape Anisotropy-Governed Locomotion of Surface Microrollers on Vessel-like Microtopographies against Physiological Flows},
     author = {Bozuyuk, Ugur and Alapan, Yunus and Aghakhani, Amirreza and Yunusa, Muhammad and Sitti, Metin},
     year = {2021},
     month = mar,
     journal = {Proceedings of the National Academy of Sciences},
     volume = {118},
     number = {13},
     publisher = {{National Academy of Sciences}},
     issn = {0027-8424, 1091-6490},
     doi = {10.1073/pnas.2022090118},
     chapter = {Physical Sciences},
     copyright = {Copyright \textcopyright{} 2021 the Author(s). Published by PNAS.. https://creativecommons.org/licenses/by/4.0/This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).},
     langid = {english},
     pmid = {33753497},
     keywords = {circulatory system,medical microrobotics,microfluidics,surface rollers,vessel microtopography}
   }

3. Lab Chip

   Flexural Wave-Based Soft Attractor Walls for Trapping Microparticles and Cells

   Amirreza Aghakhani, Hakan Cetin, Pelin Erkoc, and 2 more authors

   Lab on a Chip Mar 2021

   Bib

   @article{aghakhaniFlexuralWavebasedSoft2021a,
     ids = {aghakhani2021Flexurala},
     title = {Flexural Wave-Based Soft Attractor Walls for Trapping Microparticles and Cells},
     author = {Aghakhani, Amirreza and Cetin, Hakan and Erkoc, Pelin and Isik Tombak, Guney and Sitti, Metin},
     year = {2021},
     journal = {Lab on a Chip},
     volume = {21},
     number = {3},
     pages = {582--596},
     publisher = {{Royal Society of Chemistry}},
     doi = {10.1039/D0LC00865F},
     copyright = {All rights reserved},
     langid = {english}
   }

4. Adv. Mat.

   Liquid Crystal Structure of Supercooled Liquid Gallium and Eutectic Gallium–Indium

   Muhammad Yunusa, Alex Adaka, Amirreza Aghakhani, and 5 more authors

   Advanced Materials Mar 2021

   Bib

   @article{yunusaLiquidCrystalStructure2021,
     title = {Liquid {{Crystal Structure}} of {{Supercooled Liquid Gallium}} and {{Eutectic Gallium}}\textendash{{Indium}}},
     author = {Yunusa, Muhammad and Adaka, Alex and Aghakhani, Amirreza and Shahsavan, Hamed and Guo, Yubing and Alapan, Yunus and J{\'a}kli, Antal and Sitti, Metin},
     year = {2021},
     journal = {Advanced Materials},
     volume = {33},
     number = {38},
     pages = {2104807},
     publisher = {{Wiley Online Library}}
   }

2020

1. PNAS

   Acoustically Powered Surface-Slipping Mobile Microrobots

   Amirreza Aghakhani, Oncay Yasa, Paul Wrede, and 1 more author

   Proceedings of the National Academy of Sciences Mar 2020

   Abs Bib HTML PDF

   Untethered synthetic microrobots have significant potential to revolutionize minimally invasive medical interventions in the future. However, their relatively slow speed and low controllability near surfaces typically are some of the barriers standing in the way of their medical applications. Here, we introduce acoustically powered microrobots with a fast, unidirectional surface-slipping locomotion on both flat and curved surfaces. The proposed three-dimensionally printed, bullet-shaped microrobot contains a spherical air bubble trapped inside its internal body cavity, where the bubble is resonated using acoustic waves. The net fluidic flow due to the bubble oscillation orients the microrobot’s axisymmetric axis perpendicular to the wall and then propels it laterally at very high speeds (up to 90 body lengths per second with a body length of 25 µm) while inducing an attractive force toward the wall. To achieve unidirectional locomotion, a small fin is added to the microrobot’s cylindrical body surface, which biases the propulsion direction. For motion direction control, the microrobots are coated anisotropically with a soft magnetic nanofilm layer, allowing steering under a uniform magnetic field. Finally, surface locomotion capability of the microrobots is demonstrated inside a three-dimensional circular cross-sectional microchannel under acoustic actuation. Overall, the combination of acoustic powering and magnetic steering can be effectively utilized to actuate and navigate these microrobots in confined and hard-to-reach body location areas in a minimally invasive fashion.

   @article{aghakhaniAcousticallyPoweredSurfaceslipping2020a,
     title = {Acoustically Powered Surface-Slipping Mobile Microrobots},
     author = {Aghakhani, Amirreza and Yasa, Oncay and Wrede, Paul and Sitti, Metin},
     year = {2020},
     date = {2020-02-18},
     journal = {Proceedings of the National Academy of Sciences},
     shortjournal = {Proc Natl Acad Sci USA},
     volume = {117},
     number = {7},
     pages = {3469--3477},
     issn = {0027-8424, 1091-6490},
     doi = {10.1073/pnas.1920099117},
     url = {},
     urldate = {2021-04-14},
     langid = {english}
   }

2. Modal Analysis of Finite-Size Piezoelectric Metamaterial Plates

   Amirreza Aghakhani, Mehmet Murat Gozum, and Ipek Basdogan

   Journal of Physics D: Applied Physics Mar 2020
3. PNAS

   Bioinspired Underwater Locomotion of Light-Driven Liquid Crystal Gels

   Hamed Shahsavan, Amirreza Aghakhani, Hao Zeng, and 4 more authors

   Proceedings of the National Academy of Sciences Mar 2020

   Abs Bib

   Soft-bodied aquatic invertebrates, such as sea slugs and snails, are capable of diverse locomotion modes under water. Recapitulation of such multimodal aquatic locomotion in small-scale soft robots is challenging, due to difficulties in precise spatiotemporal control of deformations and inefficient underwater actuation of existing stimuli-responsive materials. Solving this challenge and devising efficient untethered manipulation of soft stimuli-responsive materials in the aquatic environment would significantly broaden their application potential in biomedical devices. We mimic locomotion modes common to sea invertebrates using monolithic liquid crystal gels (LCGs) with inherent light responsiveness and molecular anisotropy. We elicit diverse underwater locomotion modes, such as crawling, walking, jumping, and swimming, by local deformations induced by selective spatiotemporal light illumination. Our results underpin the pivotal role of the physicomechanical properties of LCGs in the realization of diverse modes of light-driven robotic underwater locomotion. We envisage that our results will introduce a toolbox for designing efficient untethered soft robots for fluidic environments.

   @article{shahsavanBioinspiredUnderwaterLocomotion2020a,
     title = {Bioinspired Underwater Locomotion of Light-Driven Liquid Crystal Gels},
     author = {Shahsavan, Hamed and Aghakhani, Amirreza and Zeng, Hao and Guo, Yubing and Davidson, Zoey S. and Priimagi, Arri and Sitti, Metin},
     year = {2020},
     month = mar,
     journal = {Proceedings of the National Academy of Sciences},
     volume = {117},
     number = {10},
     pages = {5125--5133},
     issn = {0027-8424, 1091-6490},
     doi = {10.1073/pnas.1917952117},
     copyright = {Copyright \textcopyright{} 2020 the Author(s). Published by PNAS.. https://creativecommons.org/licenses/by-nc-nd/4.0/This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).},
     langid = {english},
     pmid = {32094173},
     keywords = {azobenzene,biomimetics,liquid crystal gels,soft robotics,underwater locomotion}
   }

2019

1. J. Sound Vib.

   A General Electromechanical Model for Plates with Integrated Piezo-Patches Using Spectral-Tchebychev Method

   Amirreza Aghakhani, Peyman Lahe Motlagh, Bekir Bediz, and 1 more author

   Journal of Sound and Vibration Mar 2019

   Bib

   @article{aghakhaniGeneralElectromechanicalModel2019,
     title = {A General Electromechanical Model for Plates with Integrated Piezo-Patches Using Spectral-{{Tchebychev}} Method},
     author = {Aghakhani, Amirreza and Motlagh, Peyman Lahe and Bediz, Bekir and Basdogan, Ipek},
     year = {2019},
     journal = {Journal of Sound and Vibration},
     volume = {458},
     pages = {74--88},
     publisher = {{Elsevier}}
   }

2. Sci. Adv.

   Monolithic Shape-Programmable Dielectric Liquid Crystal Elastomer Actuators

   Zoey S. Davidson, Hamed Shahsavan, Amirreza Aghakhani, and 5 more authors

   Science Advances Nov 2019

   Abs Bib

   Soft robotics may enable many new technologies in which humans and robots physically interact, yet the necessary high-performance soft actuators still do not exist. The optimal soft actuators need to be fast and forceful and have programmable shape changes. Furthermore, they should be energy efficient for untethered applications and easy to fabricate. Here, we combine desirable characteristics from two distinct active material systems: fast and highly efficient actuation from dielectric elastomers and directed shape programmability from liquid crystal elastomers. Via a top-down photoalignment method, we program molecular alignment and localized giant elastic anisotropy into the liquid crystal elastomers. The linearly actuated liquid crystal elastomer monoliths achieve strain rates over 120% per second with an energy conversion efficiency of 20% while moving loads over 700 times the elastomer weight. The electric actuation mechanism offers unprecedented opportunities toward miniaturization with shape programmability, efficiency, and more degrees of freedom for applications in soft robotics and beyond.

   @article{davidsonMonolithicShapeprogrammableDielectric2019a,
     title = {Monolithic Shape-Programmable Dielectric Liquid Crystal Elastomer Actuators},
     author = {Davidson, Zoey S. and Shahsavan, Hamed and Aghakhani, Amirreza and Guo, Yubing and Hines, Lindsey and Xia, Yu and Yang, Shu and Sitti, Metin},
     year = {2019},
     month = nov,
     journal = {Science Advances},
     volume = {5},
     number = {11},
     pages = {eaay0855},
     issn = {2375-2548},
     doi = {10.1126/sciadv.aay0855},
     copyright = {All rights reserved},
     langid = {english},
     keywords = {anisotropic}
   }

3. An Investigation of the Electromechanical Coupling and Broadband Shunt Damping in Composite Plates with Integrated Piezo-Patches

   Mehmet Murat Gozum, Amirreza Aghakhani, and Ipek Basdogan

   Journal of intelligent material systems and structures Nov 2019

   Bib

   @article{gozumInvestigationElectromechanicalCoupling2019,
     title = {An Investigation of the Electromechanical Coupling and Broadband Shunt Damping in Composite Plates with Integrated Piezo-Patches},
     author = {Gozum, Mehmet Murat and Aghakhani, Amirreza and Basdogan, Ipek},
     year = {2019},
     journal = {Journal of intelligent material systems and structures},
     volume = {30},
     number = {20},
     pages = {3008--3024},
     publisher = {{SAGE Publications Sage UK: London, England}}
   }

2018

1. Multiple Piezo-Patch Energy Harvesters on a Thin Plate with Respective AC-DC Conversion

   Amirreza Aghakhani, and Ipek Basdogan

   In Active and Passive Smart Structures and Integrated Systems XII Nov 2018

   Bib

   @inproceedings{aghakhaniMultiplePiezopatchEnergy2018,
     title = {Multiple Piezo-Patch Energy Harvesters on a Thin Plate with Respective {{AC}}-{{DC}} Conversion},
     booktitle = {Active and {{Passive Smart Structures}} and {{Integrated Systems XII}}},
     author = {Aghakhani, Amirreza and Basdogan, Ipek},
     year = {2018},
     volume = {10595},
     pages = {105951B},
     publisher = {{International Society for Optics and Photonics}}
   }

2. Haptable: An Interactive Tabletop Providing Online Haptic Feedback for Touch Gestures

   Senem Ezgi Emgin, Amirreza Aghakhani, T. Metin Sezgin, and 1 more author

   IEEE transactions on visualization and computer graphics Nov 2018

   Bib

   @article{emginHaptableInteractiveTabletop2018,
     title = {Haptable: An Interactive Tabletop Providing Online Haptic Feedback for Touch Gestures},
     shorttitle = {Haptable},
     author = {Emgin, Senem Ezgi and Aghakhani, Amirreza and Sezgin, T. Metin and Basdogan, Cagatay},
     year = {2018},
     journal = {IEEE transactions on visualization and computer graphics},
     volume = {25},
     number = {9},
     pages = {2749--2762},
     publisher = {{IEEE}}
   }

3. Electroelastic Modeling of Thin-Laminated Composite Plates with Surface-Bonded Piezo-Patches Using Rayleigh–Ritz Method

   Mehmet Murat Gozum, Amirreza Aghakhani, Gokhan Serhat, and 1 more author

   Journal of Intelligent Material Systems and Structures Nov 2018

   Bib

   @article{gozumElectroelasticModelingThinlaminated2018,
     title = {Electroelastic Modeling of Thin-Laminated Composite Plates with Surface-Bonded Piezo-Patches Using {{Rayleigh}}\textendash{{Ritz}} Method},
     author = {Gozum, Mehmet Murat and Aghakhani, Amirreza and Serhat, Gokhan and Basdogan, Ipek},
     year = {2018},
     journal = {Journal of Intelligent Material Systems and Structures},
     volume = {29},
     number = {10},
     pages = {2192--2205},
     publisher = {{SAGE Publications Sage UK: London, England}}
   }

4. Seed-Mediated Synthesis of Plasmonic Gold Nanoribbons Using Cancer Cells for Hyperthermia Applications

   Ajay Vikram Singh, Yunus Alapan, Timotheus Jahnke, and 7 more authors

   Journal of Materials Chemistry B Nov 2018

   Bib

   @article{singhSeedmediatedSynthesisPlasmonic2018,
     title = {Seed-Mediated Synthesis of Plasmonic Gold Nanoribbons Using Cancer Cells for Hyperthermia Applications},
     author = {Singh, Ajay Vikram and Alapan, Yunus and Jahnke, Timotheus and Laux, Peter and Luch, Andreas and Aghakhani, Amirreza and Kharratian, Soheila and Onbasli, Mehmet Cengiz and Bill, Joachim and Sitti, Metin},
     year = {2018},
     journal = {Journal of Materials Chemistry B},
     volume = {6},
     number = {46},
     pages = {7573--7581},
     publisher = {{Royal Society of Chemistry}}
   }

5. Passive Vibration Control of a Plate via Piezoelectric Shunt Damping with FEM and ECM

   P. Lahe Motlagh, Amirreza Aghakhani, and Ipek Basdogan

   In Smart Materials and Nondestructive Evaluation for Energy Systems IV Nov 2018

   Bib

   @inproceedings{motlaghPassiveVibrationControl2018,
     title = {Passive Vibration Control of a Plate via Piezoelectric Shunt Damping with {{FEM}} and {{ECM}}},
     booktitle = {Smart {{Materials}} and {{Nondestructive Evaluation}} for {{Energy Systems IV}}},
     author = {Motlagh, P. Lahe and Aghakhani, Amirreza and Basdogan, Ipek},
     year = {2018},
     volume = {10601},
     pages = {1060103},
     publisher = {{International Society for Optics and Photonics}}
   }