arXiv subjects

Gilad Yossifon

Publications and source records attributed to Gilad Yossifon.

At least 19 recordsLinked to original sources

arXiv2025

Optoelectronically Directed Self-Assembly of Active and Passive Particles into Programmable and Reconfigurable Colloidal Structures

Controlled assembly of active-passive colloidal mixtures offers a route to reconfigurable microscale machines, but their self-assembly pathways remain poorly understood. We study the directed assembly of metallo-dielectric Janus particles (JPs) and passive polystyrene (PS) beads using optoelectrically reconfigurable AC-field patterning, which allows precise control over particle composition and binding sequence. Through experiments, analytical modeling, and simulations, we show that dipolar interactions drive robust JP-JP and JP-PS dimer formation with frequency-dependent stability. At intermediate and high frequencies, JP-PS binding is strongly attractive, whereas at low frequencies it becomes effectively repulsive due to electrical double-layer screening and electrohydrodynamic flows at the metallic hemisphere. In multi-particle systems, PS beads act as cooperative hubs that hierarchically recruit JPs, yielding higher-order hybrid structures. We identify structural isomers - for example, 3JP + 1PS clusters can form chain-like or triangular configurations depending on assembly sequence. Simulations confirm both as equilibrium states, with the triangular isomer slightly more stable. Similar polymorphism appears in larger clusters (4JPs). Overall, we establish a framework for controlled active-passive colloidal assembly, showing how frequency-tunable interactions and structural polymorphism enable the design of reconfigurable colloidal machines for applications in microrobotics, targeted delivery, and adaptive materials.

cond-mat.soft↗

arXiv2025

Dielectrophoretic response and electro-deformation of soft bioparticles interacting with a metallo-dielectric Janus active particle

Active (self-propelling) particles have emerged as innovative microscale tools in the field of single cell analysis with the advantages of being untethered, remotely controlled, hybrid powered, with sub-cellular precision. This study investigates the dielectrophoretic (DEP) response and electro-mechanical deformation of cell nuclei interacting with active metallo-dielectric Janus Particles (JPs) under an externally applied electric field. An equivalent droplet two-phase model is employed to simulate the bioparticle, coupling the Navier-Stokes equations with the Phase Field Model to capture fluid motion and interface dynamics. Good qualitative agreement is obtained among experimental, analytical, and numerical results. The findings reveal a nonlinear relationship between nucleus deformation and its surface coverage of the JP with respect to the applied voltage. The overall coverage ratio of the JP dielectric hemisphere increases with voltage as the positive DEP force on the dielectric side strengthens, exhibiting maximum at a certain voltage. The strong correlation between nucleus flexibility and JP surface coverage suggests that the JP coverage ratio could serve as a biomechanical marker for nucleus deformability, providing a novel method for in-situ evaluation of nucleus mechanics.

cond-mat.soft↗

arXiv2025

Hybrid Magnetically and Electrically Powered Metallo-Dielectric Janus Microrobots: Enhanced Motion Control and Operation Beyond Planar Limits

This study introduces the integration of hybrid magnetic and electric actuation mechanisms to achieve advanced motion capabilities for Janus particle (JP) microrobots. We demonstrate enhanced in-plane motion control through versatile control strategies and present the concepts of interplanar transitions and 2.5-dimensional (2.5D) trajectories, enabled by magnetic levitation and electrostatic trapping. These innovations expand the mobility of JPs into 3D space, allowing dynamic operation beyond the limitations of traditional surface-bound motion. Key functionalities include obstacle crossing, transitions to elevated surfaces, and discrete surface patterning enabling highly localized interventions. Using this set of tools, we also showcase the controlled out-of-plane transport of both synthetic and biological cargo. Together, these advancements lay the groundwork for novel microrobot-related applications in microfluidic systems and biomedical research.

cs.RO↗

arXiv2024

Toward an Ion-Based Large-Scale Integrated Circuit: Circuit Level Design, Simulation, and Integration of Iontronic Components

Iontronics combines ions as charge carriers with electronic-like operations, enabling unique information processing, chemical regulation, and enhanced bio-integrability. Standard simulation tools encounter difficulties in effectively modeling the behavior of integrated iontronic components, highlighting the need for specialized design and simulation approaches. This paper presents a design methodology for iontronic integrated circuits, inspired by well-established electronic design methodologies and made possible by the development of a compact model for the iontronic bipolar diode. Grounded in the diode's physical properties and observed behavior, this model provides a conceptual framework that could be applied to other iontronic components. It is implemented using standard VLSI (Very Large-Scale Integration) electronic design tools, enabling simulations that demonstrate diode-based iontronic circuit behaviors and laying the groundwork for the design and simulation of hybrid systems integrating electronic and iontronic circuits. The proposed iontronic circuit simulation approach enables the exploration of how component uniformity influences circuit behavior, as well as the impact of diode parameters and a deeper understanding of diode characteristics from a circuit perspective. These insights are expected to contribute to the development of more complex and efficient iontronic circuits, bringing us closer to practical and groundbreaking applications in the field.

cs.ET↗

arXiv2024

Understanding the Origin of a Second Mobility Reversal in Optoelectrically Powered Metallo-Dielectric Janus Particles

While previous studies indicated the mobility reversal of an electrically-powered metallo-dielectric Janus particle (JP) with increasing frequency, here we report an intriguing second mobility reversal observed in optoelectronically-driven JPs. In contrast to the commonly used setup with parallel ITO-coated glass substrates to induce a uniform electric field orthogonal to the velocity direction, this setup incorporates a thin photoconductive layer deposited on the bottom ITO-coated glass substrate. We have found that the reversal is associated with the asymmetry of the bottom substrate's photoconductivity, localized underneath the JP, resulting from the self-shading effect of the metallic hemisphere under top optical illumination. Numerous control tests, including optical illumination from the bottom, along with numerical simulations, support this hypothesized mechanism

cond-mat.mtrl-sci↗

arXiv2024

Biohybrid Microrobots Based on Jellyfish Stinging Capsules and Janus Particles for In Vitro Deep-Tissue Drug Penetration

Microrobots engineered from self-propelling active particles, extend the reach of robotic operations to submillimeter dimensions and are becoming increasingly relevant for various tasks, such as manipulation of micro/nanoscale cargo, particularly targeted drug delivery. However, achieving deep-tissue penetration and drug delivery remain a challenge. This work developed a novel biohybrid microrobot consisting of jellyfish stinging capsules, which act as natural nanoinjectors for efficient penetration and delivery, assembled onto an active Janus particle (JP). While microrobot transport and navigation was externally controlled by magnetic field-induced rolling, capsule loading onto the JP surface was controlled by electric field. Following precise navigation of the biohybrid microrobots to the vicinity of target tissues, the capsules were activated by a specific enzyme introduced to the solution, which then triggered tubule ejection and release of the preloaded molecules. Use of such microrobots for penetration of and delivery of the preloaded drug/toxin to targeted cancer spheroids and live Caenorhabditis elegans was demonstrated in-vitro. The findings offer insights for future development of bio-inspired microrobots capable of deep penetration and drug delivery. Future directions may involve encapsulation of various drugs within different capsule types for enhanced versatility. This study may also inspire in-vivo applications involving deep tissue drug delivery.

cs.RO↗

arXiv2024

Programmable Motion of Optically Gated Electrically Powered Engineered Microswimmer Robots

Here, we report on a new class active particles capable of dynamically programmable motion powered by electricity. We have implemented physical principles that separate the propulsion and steering mechanisms of active motion using optically activated, patterned, photoresponsive semiconductor coatings on intricate microstructures. Our engineered microswimmer robots employ an induced-charge electro-phoresis (ICEP) mechanism to achieve linear motion and optically modulated electrokinetic propulsion (OMEP) for steering. Optical modulation is achieved by manipulating the polarizability of patterned ZnO semiconductor coating through exposure to light with wavelengths above its bandgap, exploiting the semiconductor's photoconductive properties. Unlike previous methods that rely on changing the direction of optical illumination or spatially controlling narrow optical beams, our approach achieves optical steering under uniform ambient illumination conditions, thereby greatly reducing the complexity of the optical system. The decoupling of propulsion and steering allows for the programming of micromotor trajectories in both open and closed-loop control modes. We anticipate that our findings will pave the way for efficient optically gated control of the trajectory of photoresponsive active particles. Furthermore, they will enable the selective manipulation of specific subgroups of engineered active microparticles with various semiconducting coatings having different band gaps.

cond-mat.soft↗

arXiv2023

Optoelectronic Trajectory Reconfiguration and Directed Self-Assembly of Self-Propelling Electrically-Powered Active Particles

Self-propelling active particles are an exciting and interdisciplinary emerging area of research with projected biomedical and environmental applications. Due to their autonomous motion, control over these active particles that are free to travel along individual trajectories, is challenging. This work used optically patterned electrodes on a photoconductive substrate using a digital micromirror device (DMD) to dynamically control the region of movement of self-propelling particles (i.e. metallo-dielectric Janus particles (JPs)). This extends previous studies where only a passive micromotor was optoelectronically manipulated with a translocating optical pattern that illuminated the particle. In contrast, the current system used the optically patterned electrode merely to define the region within which the JPs moved autonomously. Interestingly, the JPs avoided crossing the optical region edge, which enables constraint of the area of motion and to dynamically shape the JP trajectory. Using the DMD system to simultaneously manipulate several JPs enabled to self-assemble the JPs into stable active structures (JPs ring) with precise control over the number of participating JPs and passive particles. Since the optoelectronic system is amenable to closed-loop operation using real-time image analysis, it enables exploitation of these active particles as active microrobots that can be operated in a programmable and parallelized manner

physics.flu-dyn↗

arXiv2022

A Magnetically and Electrically Powered Hybrid Micromotor in Conductive Solutions: Synergistic Propulsion Effects and Label-Free Cargo Transport and Sensing

Electrically powered micro- and nanomotors are promising tools for in-vitro single-cell analysis. In particular, single cells can be trapped, transported and electroporated by a Janus particle (JP) using an externally applied electric field. However, while dielectrophoretic (DEP)-based cargo manipulation can be achieved at high-solution conductivity, electrical propulsion of these micromotors becomes ineffective at solution conductivities exceeding 0.3mS/cm. Here, we successfully extended JP cargo manipulation and transport capabilities to conductive near-physiological (<6mS/cm) solutions by combining magnetic field-based micromotor propulsion and navigation with DEP-based manipulation of various synthetic and biological cargos. Combination of a rotating magnetic field and electric field resulted in enhanced micromotor mobility and steering control through tuning of the electric field frequency. conditions are necessary. In addition, we demonstrated the micromotors ability of identifying apoptotic cell among viable and necrotic cells based their dielectrophoretic difference, thus, enabling to analyze the apoptotic status in the single cell samples for drug discovery, cell therapeutics and immunotherapy. We also demonstrated the ability to trap and transport live cells towards regions containing doxorubicin-loaded liposomes. This hybrid micromotor approach for label-free trapping, transporting and sensing of selected cells within conductive solutions, opens new opportunities in drug delivery and single cell analysis, where close-to-physiological media

physics.flu-dyn↗

arXiv2022

Designing with Iontronic Logic Gates -- From a Single Polyelectrolyte Diode to Small Scale Integration

This article presents the implementation of on-chip iontronic circuits via small-scale integration of multiple ionic logic gates made of bi-polar polyelectrolyte diodes. These ionic circuits are analogous to solid-state electronic circuits, with ions as the charge carriers instead of electrons/holes. We experimentally characterize the responses of a single fluidic diode made of a junction of oppositely charged polyelectrolytes (i.e., anion and cation exchange membranes), with a similar underlying mechanism as a solid-state p- and n-type junction. This served to carry out pre-designed logical computations in various architectures by integrating multiple diode-based logic gates, where the electrical signal between the integrated gates was transmitted entirely through ions. The findings shed light on the limitations affecting the number of logic gates that can be integrated, the degradation of the electrical signal, their transient response, and the design rules that can improve the performance of iontronic circuits.

physics.flu-dyn↗

arXiv2022

Electro-Orientation and Electro-Rotation of Metallodielectric Janus Particles

The electro-rotation (EROT) and electro-orientation (EOR) behavior of metallodielectric (MD) spherical Janus particles (JP) are studied analytically and verified experimentally. This stands in contrast to previous either heuristic or numerically computed models of JP dipoles. First, we obtain frequency-dependent analytic expressions for the corresponding dipole terms for a JP composed of a dielectric and metallic hemispheres, by applying the standard (weak-field) electrokinetic model and using a Fourier-Legendre collocation method for solving two sets of linear equations. EROT and EOR spectra, describing the variation of the JP angular velocity on the forcing frequency of a rotating and non-rotating spatially uniform electric field, respectively, are explicitly determined and compared against experiments (different JP size and solution conductivity). A favorably good qualitative agreement between theory and experimental measurements was found.

physics.flu-dyn↗

arXiv2022

Microvalve-Based Tunability of Electrically Driven Ion Transport Through a Microfluidic System with Ion-Exchange Membrane

Microfluidic channels with embedded ion permselective medium under the application of electric current are commonly used for electrokinetic processes as on-chip ion concentration polarization (ICP) and bioparticle preconcentration to enhance biosensing. Herein, we demonstrate the ability to dynamically control the electrically driven ion transport by integrating individually addressable microvalves. The microvalves are located along a main microchannel that is uniformly coated with a thin layer of an ion-exchange membrane (IEM). The interplay of ionic transport between the solution within the microchannel and the thin IEM, under an applied electric current, can be locally tuned by the deformation of the microvalve. This tunability provides a robust and simple means of implementing new functionalities into lab-on-a-chip devices, e.g., dynamic control over multiple ICP layers and their associated preconcentrated molecule plugs, multiplex sensing, suppression of biofouling as well as plug dispersion, while maintaining the well-known application of microvalves as steric filtration.

physics.flu-dyn↗

arXiv2022

Optically Modulated Propulsion of Electric Field Powered Photoconducting Janus Particles

Herein we demonstrate the ability to optically tune the mobility of electrically powered Janus particles (JP) that are half coated with various Zinc Oxide (ZnO) semiconducting layers, i.e. polycrystalline, amorphous and amorphous with a SiO2 passivation layer. The ZnO semiconductor photo-response enables increase in its electrical conductivity with light having wavelengths of sufficient photon energy with respect to the semiconductor bandgap. This effect, termed optically modulated electrokinetic propulsion (OMEP), can be harnessed to increase the contrast in polarizability between the dielectric and semiconducting hemispheres, which in turn, results in an increased electrokinetic mobility. The addition of optical activation to the electrical field enables an additional degree of control of JP mobility. We also demonstrate optical control of collective behavior and particle-particle interactions for dense semi-conducting Janus particle populations.

cond-mat.mtrl-sci↗

arXiv2020

Periodic Concentration-Polarization-Based Formation of a Biomolecule Preconcentrate for Enhanced Biosensing

Ionic concentration-polarization (CP)-based biomolecule preconcentration is an established method for enhancing the detection sensitivity of target biomolecules. However, the formed preconcentrated biomolecule plug rapidly sweeps over the surface-immobilized antibodies, resulting in a short-term overlap between the capture agent and the analyte, and subsequently suboptimal binding. To overcome this, we designed a setup allowing for periodic formation of a preconcentrated biomolecule plug by activating the CP for predetermined on/off intervals. This work demonstrated the feasibility of the cyclic CP actuation and optimized the sweeping conditions required to obtain maximum retention time of a preconcentrated plug over a desired sensing region and enhanced detection sensitivity. The ability of this method to efficiently preconcentrate different analytes and to successfully increase immunoassay sensitivity, underscore its potential in immunoassays serving the clinical and food testing industries.

physics.app-ph↗

arXiv2020

Dielectrophoretic Equilibrium of Complex Particles

In contrast to the commonly used spherical Janus particles, here we used engineered Janus particles that are fabricated using photolithography technique for precise control over their geometry and coated regions. Specifically, we studied a lollipop-shaped complex particle where its head is coated with gold while its tail is left bare. Due to their distinct electrical properties (i.e. electrical polarizability) the particle exhibits force equilibrium where opposite dielectrophoretic forces acting on its head and tail exactly cancel each other to yield a stable equilibrium position. This was realized in a quadrupolar electrode array where the equilibrium position of the engineered particle could be tuned by the frequency. This stands in contrast to the standard dielectrophoretic behavior where the particle shifts positions from either the center of the quad to the very edge of the electrodes when shifting from a negative to positive dielectrophoretic response, respectively. This opens new opportunities for positioning control of such complex particles for self-assembly, biosensing, biomimetic spermatozoa and more.

cond-mat.soft↗

arXiv2019

Active Particles as Mobile Microelectrodes for Selective Bacteria Electroporation and Transport

Self-propelling micromotors are emerging as a promising microscale and nanoscale tool for single-cell analysis. We have recently shown that the field gradients necessary to manipulate matter via dielectrophoresis can be induced at the surface of a polarizable active (self-propelling) metallo-dielectric Janus particle (JP) under an externally applied electric field, acting essentially as a mobile floating microelectrode. Here, we successfully demonstrated for the first time, that the application of an external electric field can singularly trap and transport bacteria and can selectively electroporate the trapped bacteria. Selective electroporation, enabled by the local intensification of the electric field induced by the JP, was obtained under both continuous alternating current and pulsed signal conditions. This approach is generic and is applicable to bacteria and JP, as well as a wide range of cell types and micromotor designs. Hence, it constitutes an important and novel experimental tool for single-cell analysis and targeted delivery.

cond-mat.soft↗

arXiv2019

Analysis of Cargo Loading Modes and Capacity of an Electrically-Powered Active Carrier

The use of active colloids for cargo transport offers unique potential for applications ranging from targeted drug delivery to lab-on-a-chip systems. Previously, Janus particles (JPs), acting as mobile microelectrodes have been shown to transport cargo which is trapped by a dielectrophoretic mechanism [Boymelgreen et al. (2018)]. Herein, we aim to characterize the cargo loading properties of mobile Janus carriers, across a broad range of frequencies and voltages. In expanding the frequency range of the carrier, we are able to compare the influence of different modes of carrier transport on the loading capacity as well as highlight the differences between cargo trapped by positive and negative dielectrophoresis. Specifically it is shown that cargo trapping results in a reduction in carrier velocities with this effect more pronounced at low frequencies where cargo is trapped close to the substrate. Interestingly, we observe the existence of a maximum cargo loading capacity which decreases at large voltages suggesting a strong interplay between trapping and hydrodynamic shear. Finally, we demonstrate that control of the frequency can enable different assemblies of binary colloidal solutions on the JP. The resultant findings enable the optimization of electrokinetic cargo transport and its selective application to a broad range of targets.

cond-mat.soft↗

arXiv2019

Electrothermal active control of preconcentrated biomolecule plugs

Concentration polarization (CP) based biomolecule preconcentration is highly effective in enhancing the detection sensitivity, yet fails to precisely and dynamically control the location of the preconcentrated biomolecule plug to ensure overlap with the sensing region (e.g. immobilized molecular probes). Here, we used electrothermal (ET) stirring as a means of controlling the location of a preconcentrated biomolecule plug. The applied microfluidic device consisted of a Nafion membrane to induce the CP, and an array of individually addressable microscale heaters for active local ET stirring. The experimental results demonstrated that such a novel platform enabled active control of the location of the preconcentrated plug of target biomolecules, ensuring its overlap with the functionalized microparticles, ultimately yielding enhanced detection sensitivity and binding kinetics. This was demonstrated using avidin-biotin particles as a simple bead-based bioassay model.

cond-mat.soft↗