Sambeeta Das

• PhD, Pennsylvania State University
• PostDoc Position at University of Pennsylvania

Artificial active colloids are an active area of research in the field of active matter and microrobotic systems. In particular, light‐driven semiconductor particles are shown to display interesting behaviors ranging from phototaxis (movement toward or away from a light source), rising from the substrate, interparticle attraction, attraction to the...

Control of individual micromotors within a group would allow for improved efficiency, greater ability to accomplish complex tasks, higher throughput, and increased adaptability. However, independent control of micromotors remains a...

The field of microrobotics has emerged as a promising area of research with significant applications in biomedicine, both in vitro and in vivo, such as targeted cargo delivery, microsurgery, and cellular manipulation. Microrobots actuated with multiple modalities have the potential for greater adaptability, robustness, and capability to perform var...

The field of microrobotics has immensely grown in the last few decades, exhibiting several challenges as new features such as shapes, sizes, and actuation mechanisms are explored. Two of the biggest challenges faced in microrobotics are the development of a control system suited for precise microrobotic manipulation, and the ability to navigate mic...

This paper presents a control framework for magnetically actuated micron-scale robots ($\mu$bots) designed to mitigate disturbances and improve trajectory tracking. To address the challenges posed by unmodeled dynamics and environmental variability, we combine data-driven modeling with model-based control to accurately track desired trajectories us...

Micron-scale robots (μbots) have recently shown great promise for emerging medical applications. Accurate control of μbots, while critical to their successful deployment, is challenging. In this work, we consider the problem of tracking a reference trajectory using a μbot in the presence of disturbances and uncertainty. The disturbances primarily c...

This research introduces a quadrupole magnetic tweezers which can be used for precise cell transportation by actuating magnetic spherical microrobots. The focus of the system is on navigating and manipulating cells within environments characterized by high cellular density. Demonstrating efficacy in moving cells through densely packed cell samples,...

Micromotors have been proposed for applications such as targeted drug delivery, thrombolysis, or sensing. However, single micrormotors are limited in the amount of payload they can deliver or force they can exert. Swarms of micromotors can overcome many of these challenges, however creating and controlling such swarms presents many challenges of it...

Mobile magnetic microrobots have been extensively used in a wide range of in vitro biomedical applications due to their numerous advantages. Magnetic microrobots in particular have been developed and shown great potential over the past two decades for the manipulation and migration of both single cells and cell aggregates. The efficient clearance o...

Microrobots, untethered miniature devices capable of performing tasks at the microscale, have gained significant attention in the fields of robotics and biomedicine. These devices hold immense potential for various industrial and scientific applications, including targeted drug delivery and cell manipulation. In this study, we present a novel magne...

Micro-sized magnetic particles (also known as microrobots [MRs]) have recently been shown to have potential applications for numerous biomedical applications like drug delivery, microengineering, and single cell manipulation. Interdisciplinary studies have demonstrated the ability of these tiny particles to actuate under the action of a controlled...

Liquid–liquid or liquid–air interfaces provide interesting environments to study colloids and are ubiquitous in nature and industry, as well as relevant in applications involving emulsions and foams. They present a particularly intriguing environment for studying active particles that exhibit a host of phenomena not seen in passive systems. Active...

Mobile microrobots have the potential to transform medical treatments based on therapeutic delivery. Specifically, microrobots are promising candidates for cell transportation in cell-based therapies. Despite recent progress in cellular manipulation by microrobots, there is a significant need to design and fabricate microrobots to advance the field...

Using a spatially varying light pattern with light activated semi‐conductor based magnetic micromotors, we study the difference in micromotor flux between illuminated and non‐illuminated regions in the presence and absence of an applied magnetic field. We find that the magnetic field enhances the flux of the motors which we attribute to a straighte...

In this study, we propose a simple and efficient method to fabricate three-lobed nonspherical Janus microrobots. These microrobots can be actuated by a harmless magnetic field. Utilizing organosilica as the material of choice, we leverage its versatile silane chemistry to enable various surface modifications and functionalities. The fabricated micr...

Our study presents an accurate and automated control mechanism for Janus micromotors powered by catalytic reactions. This system utilizes fully controllable electromagnetic coils to direct the magnetic field toward a reference point, causing the particles to move in response to the catalytic decomposition of hydrogen peroxide. Magnetic torques with...

Electromagnetic systems have been used extensively for the control of magnetically actuated objects, such as in microrheology and micro- robotics research. Therefore, optimizing the design of such systems is highly desirable. Some of the features that are lacking in most cur- rent designs are compactness, portability, and versatility. Portability i...

Micron-scale robots (ubots) have recently shown great promise for emerging medical applications, and accurate control of ubots is a critical next step to deploying them in real systems. In this work, we develop the idea of a nonlinear mismatch controller to compensate for the mismatch between the disturbed unicycle model of a rolling ubot and traje...

Therapeutic delivery of anti-cancer drugs is a major goal of modern medicine. In particular, microrobots (MRs) have recently been studied for their ability to navigate difficult-to-reach regions in the human body to deliver therapeutics for microscopically localized interventions. However, the control of individual and swarms of MRs to precisely ta...

Untethered robots of the size of a few microns have attracted increasing attention for the potential to transform many aspects of manufacturing, medicine, health care, and bioengineering. Previously impenetrable environments have become available for high-resolution in situ and in vivo manipulations as the size of the untethered robots goes down to...

Therapeutic delivery of anti-cancer drugs is a major goal of modern medicine. In particular, microrobots (MRs) have recently been studied for their ability to navigate difficult-to-reach regions in the human body to deliver therapeutics for microscopically localized interventions. However, the control of individual and swarms of MRs to precisely ta...

We report a closed-loop control system for paramagnetic catalytically self-propelled Janus microrobots. We achieve this control by employing electromagnetic coils that direct the magnetic field in a desired orientation to steer the microrobots. The microrobots move due to the catalytic decomposition of hydrogen peroxide, during which they align the...

Electromagnetic systems have been used extensively for the control magnetically actuated objects, such as in microrheology and microrobotics research. Therefore, optimizing the design of such systems is highly desired. Some of the features that are lacking in most current designs are compactness, portability, and versatility. Portability is especia...

The control of swarm systems is relatively well understood for simple robotic platforms at the macro scale. However, there are still several unanswered questions about how similar results can be achieved for microrobots. In this paper, we propose a modeling framework based on a dynamic model of magnetized self-propelling Janus microrobots under a g...

cell-membrane fusion using microrobots can be a useful technique for delivering bioactive compounds to cellular systems. The role of membrane curvature and lipid ordering in the cell membrane penetration process is well known. However, once the fusion into the cell membrane is already initiated, the fluid dynamics of microrobot penetration based on...

Many biomedical applications, such as targeted drug delivery or cell manipulation, are well suited for the deployment of microrobots, untethered devices that are capable of carrying out tasks at the microscale. One biocompatible means of driving microrobots relies on magnetic actuation. In particular, microrobots driven using rotating fields rather...

Having the advantage of being relatively fast and powerful, as well as readily fabricated, spherical bubble-propelled microrobots are particularly well suited for applications such as cargo delivery, micromanipulation, and biological or environmental remediation. However, there have been limited examples of control and manipulation with these micro...

The control of swarm systems is relatively well understood for simple robotic platforms at the macro scale. However, there are still several unanswered questions about how similar results can be achieved for microrobots. In this paper, we propose a modeling framework based on a dynamic model of magnetized self-propelling Janus microrobots under a g...

Microrobots have many potential uses in microbiology since they can be remotely actuated and precisely manipulated in biochemical fluids. Cellular function and response depends on biochemicals. Therefore, various delivery methods have been developed for delivering biologically relevant cargo using microrobots. However, localized targeting without p...

The ability to direct microrobots in the low Reynolds number regime has broad applications in engineering, biology and medicine. In contrast to externally driven robots, catalytically driven microrobots utilize chemical reactions to hyphenate all instances in solution. Controlling multiple self propelled microrobots in the same workspace has been a...

The directed transport of microparticles in microfluidic devices is vital for efficient bioassays and fabrication of complex microstructures. There remains, however, a need for methods to propel and steer microscopic cargo that do not require modifying these particles. Using theory and experiments, we show that catalytic surface reactions can be us...

The video (a snapshot is shown in Supplementary Figure 1) shows convective transport of 500 tracers in a three-dimensional rectangular domain (3 mm × 1 mm × 3 mm). The enzyme (catalase) on the bottom plane coats a pattern consisting of parallel stripes oriented along the z-direction (similar to the experimental setup shown in Fig. 6). The stripe wi...

The video (a snapshot is shown in Supplementary Figure 2) shows convective transport of 500 tracers in a three-dimensional rectangular domain (3 mm × 1 mm × 3 mm) with catalase homogeneously coating the whole bottom plane. The reaction rate per unit area on the bottom is rmax= 0.85×10−3 molm−2s−1, which is half of the rate used on the stripes in Su...

The urease pump is comprised of strips of gold with enzymes attached to them and the gel is soaked with 500 mM urea in phosphate buffer. 2 μm (radius) tracer particles demonstrate the direction of the flow after 5 min. As we change the focal plane and move vertically in the system, the reversal of the direction of tracer particles is seen, due to f...

Supplementary Notes and Supplementary Figures

The video shows results presented in Fig. 2 for C0= 0.1 M and rmax= 1.7×10−5 mol m−2s−1. The results presented in Fig. 3, 4, and 5 for C0= 0.1 M at other reaction rates demonstrate similar behavior.

The video shows results presented in Fig. 5 for C0= 0.2 M and rmax= 1.7×10−2 mol m−2s−1. The results presented in Fig. 5 for C0= 0.2 M at other reaction rates demonstrate similar behavior.

The platinum pump is comprised of strips of platinum and the gel is soaked with 0.59 M H2O2. 2 μm (radius) tracer particles demonstrate the direction of the flow after 5 min. As we change the focal plane and move vertically in the system, the reversal of the direction of tracer particles is seen, due to fluid continuity.

The platinum pump is comprised of strips of platinum and the gel is soaked with 0.29 M H2O2. The video was taken after 60 min. As we move along the pattern, the settled tracers can be seen and the changes in their density can be measured.

The video shows results presented in Fig. 5 for C0= 0.05 M and rmax= 1.7×10−2 mol m−2s−1. The results presented in Fig. 5 for C0= 0.05 M at other reaction rates demonstrate similar behavior.

The platinum pump is comprised of strips of platinum and the gel is soaked with DI water. 2 μm (radius) tracer particles demonstrate the absence of the flow after 5 min, with the tracers undergoing Brownian diffusion.

The urease pump is comprised of strips of gold with enzymes attached to them and the gel is soaked with phosphate buffer only. 2 μm (radius) tracer particles demonstrate the absence of the flow after 5 min, with the tracers undergoing Brownian diffusion.

The urease pump is comprised of strips of gold with enzymes attached to them and the gel is soaked with 500 mM urea in phosphate buffer. The video was taken after 60 min. As we move along the pattern, the settled tracers can be seen and the changes in their density can be measured.

The advent of autonomous self-propulsion has instigated research towards making colloidal machines that can deliver mechanical work in the form of transport, and other functions such as sensing and cleaning. While much progress has been made in the last 10 years on various mechanisms to generate self-propulsion, the ability to steer self-propelled...

Synthetic nano- and microscale machines move autonomously in solution or drive fluid flows by converting sources of energy into mechanical work. Their sizes are comparable to analytes (sub-nano- to microscale), and they respond to signals from each other and their surroundings, leading to emergent collective behavior. These machines can potentially...

We demonstrate a procedure for the separation of enzymes based on their chemotactic response towards an imposed substrate concentration gradient. The separation is observed within a two-inlet, five-outlet microfluidic network, designed to allow mixtures of active (ones that catalyze substrate turnover) and inactive (ones that do not catalyze substr...