Brad Nelson

ETH Zurich | ETH Zürich · Department of Mechanical and Process Engineering

Activity and autonomous motion are fundamental aspects of many living and engineering systems. Here, the scale of biological agents covers a wide range, from nanomotors, cytoskeleton, and cells, to insects, fish, birds, and people. Inspired by biological active systems, various types of autonomous synthetic nano- and micromachines have been designe...

The limited bioavailability, susceptibility to degradation, and adverse side effects of novel drugs often hinder their effective administration. Nanoparticles, with customizable properties and small size, have emerged as potential carriers, though their delivery efficiency remains low. With their ability to navigate fluid environments, micro- and n...

Interfacial strain engineering in ferroic nanomembranes can broaden the scope of ferroic nanomembrane assembly as well as facilitate the engineering of multiferroic‐based devices with enhanced functionalities. Geometrical engineering in these material systems enables the realization of 3‐D architectures with unconventional physical properties. Here...

Covalent Organic Frameworks (COFs) emerged as versatile materials with promising potential in biomedicine. Their customizable functionalities and tunable pore structures make them valuable for various biomedical applications such as biosensing, bioimaging, antimicrobial activity, and targeted drug delivery. Despite efforts made to create nanoscale...

Teleoperated robotic surgery is a rapidly growing field that promises to overcome geographical barriers and share expertise over long distances for a variety of minimally invasive procedures. A particularly promising technology for teleoperation is robotic magnetic navigation. In contrast to conventional surgical robots, a robotic magnetic navigati...

The initial delivery of small‐scale magnetic devices such as microrobots is a key, but often overlooked, aspect for their use in clinical applications. The deployment of these devices within the dynamic environment of the human body presents significant challenges due to their dispersion caused by circulatory flows. Here, a method is introduced to...

Regenerative medicine continually seeks effective methods to address spinal cord injuries (SCI), which are known for their limited regenerative potential. Despite advances in neural progenitor cell (NPC) transplants for spinal cord injuries, challenges related to graft survival, reliable in vivo differentiation, and neural integration significantly...

Iron oxide nanoparticles hold great potential for future biomedical applications but, to date, usually suffer from reduced magnetic properties compared to their bulk counterparts. The replacement of Fe(III) ions with Zn(II) ions can enhance their magnetic properties while keeping their biocompatibility characteristics. Yet, common synthesis methods...

Soft materials play a crucial role in small‐scale robotic applications by closely mimicking the complex motion and morphing behavior of organisms. However, conventional fabrication methods face challenges in creating highly integrated small‐scale soft devices. In this study, microfluidics is leveraged to precisely control reaction‐diffusion (RD) pr...

A major obstacle in applying machine learning for medical fields is the disparity between the data distribution of the training images and the data encountered in clinics. This phenomenon can be explained by inconsistent acquisition techniques and large variations across the patient spectrum. The result is poor translation of the trained models to...

Surface-engineered magnetic microparticles are used in chemical and biomedical engineering due to their ease of synthesis, high surface-to-volume ratio, selective binding, and magnetic separation. To separate them from fluid suspensions, existing methods rely on the magnetic force introduced by the local magnetic field gradient. However, this strat...

The advent of surgical robots has significantly enhanced the precision and efficiency of surgical procedures, paving the way for remote operation and telesurgery. Despite its potential for delivering expert care to remote regions and aiding in surgical training, the widespread adoption of telesurgery has been hindered by various challenges. To over...

Magnetic navigation systems are used to precisely manipulate magnetically responsive materials enabling the realization of new minimally invasive procedures using magnetic medical devices. Their widespread applicability has been constrained by high infrastructure demands and costs. The study reports on a portable electromagnetic navigation system,...

Thermal decomposition of iron oleate is a simple and widespread method for synthesizing monodispersed iron oxide nanoparticles (IONPs) with well‐defined morphology. However, the complexity of the underlying mechanism makes this method rather sensitive to variations in experimental conditions, and the lack of simple techniques to monitor the reactio...

Resonant electromagnetic navigation systems generate controllable oscillating and rotating magnetic fields using resonant electronic networks. This modality holds great potential to control untethered magnetic robots remotely for medical applications using fast rotating magnetic fields. However, the performance of these systems is limited at increa...

Endoscopes navigate within the human body to observe anatomical structures with minimal invasiveness. A major shortcoming of their use is their narrow field‐of‐view during navigation in large, hollow anatomical regions. Mosaics of endoscopic images can provide surgeons with a map of the tool's environment. This would facilitate procedures, improve...

Medical devices actuated by external magnetic fields can create opportunities for clinical adoption of precision telesurgery.

Treating vascular diseases in the brain requires access to the affected region inside the body. This is usually accomplished through a minimally invasive technique that involves the use of long, thin devices, such as wires and tubes, that are manually maneuvered by a clinician within the bloodstream. By pushing, pulling, and twisting, these devices...

Electric fields have been highlighted as a smart reagent in nature’s enzymatic machinery, as they can directly trigger or accelerate chemical processes with stereo- and regio-specificity. In enzymatic catalysis, controlled mass transport of chemical species is also key in facilitating the availability of reactants in the active reaction site. Howev...

Cardiac arrhythmia affects a large portion of the population, particularly the elderly. As the population ages, the number of patients suffering from this condition is expected to rise, underlining the importance of more efficient treatment methods. Radio-frequency (RF) catheter ablation is the treatment of choice for many cardiac arrhythmias. To r...

In minimally invasive surgery, such as cardiac ablation, magnetically steered catheters made of variable‐stiffness materials can enable higher dexterity and higher force application to human tissue. However, the long transition time between soft and rigid states leads to a significant increase in procedure duration. Here, a fast‐response, multisegm...

Magnetic microrobots have shown promise in the field of biomedical engineering, facilitating precise drug delivery, non-invasive diagnosis and cell-based therapy. Current techniques for controlling the motion of such microrobots rely on the assumption of homogenous magnetic fields and are significantly influenced by a microrobot’s properties and su...

Covalent organic frameworks (COFs) are crystalline materials with intrinsic porosity that offer a wide range of potential applications spanning diverse fields. Yet, the main goal in the COF research area is to achieve the most stable thermodynamic product while simultaneously targeting the desired size and structure crucial for enabling specific fu...

Magnetic microrobots have been developed for navigating microscale environments by means of remote magnetic fields. However, limited propulsion speeds at small scales remain an issue in the maneuverability of these devices as magnetic force and torque are proportional to their magnetic volume. Here, a microrobotic superstructure is proposed, which,...

An increasing presence of robotics and artificial intelligence in the Global South calls for responsible implementation.

*** Full paper available here: https://www.research-collection.ethz.ch/handle/20.500.11850/646580 *** Remote magnetic navigation provides a promising approach for improving the maneuverability and safety of surgical tools, such as catheters and endoscopes, in complex anatomies. The lack of existing localization systems compatible with this modalit...

Biomedical microrobots could overcome current challenges in targeted therapies

A long-standing challenge in skeletal tissue engineering is to reconstruct a three-dimensionally (3D) interconnected bone cell network in vitro that mimics the native bone microarchitecture. While conventional hydrogels are extensively used in studying bone cell behavior in vitro, current techniques lack the precision to manipulate the complex peri...

Synthetic micromotor has gained substantial attention in biomedicine and environmental remediation. Metal-based degradable micromotor composed of magnesium (Mg), zinc (Zn), and iron (Fe) have promise due to their nontoxic fuel-free propulsion, favorable biocompatibility, and safe excretion of degradation products Recent advances in degradable metal...

Microrobots have a high demand for multi‐agent control to enhance their effectiveness in performing various tasks. While light is a power source that can control many micro‐structures, the range of controllable objects is limited to polymeric structures, simple particles, or bio‐cells. This study presents a multi‐agent microrobot control platform t...

Microrobots have shown great potential in many applications, such as non‐invasive surgery, tissue engineering, precision medicine, and environmental remediation. Within the past decade, soft microrobot has become one of the important branches. It is aimed to create soft and deformable microrobots with high bioaffinity, which can perform complex tas...

Piezoelectric nanomaterials have become increasingly popular in the field of biomedical applications due to their high biocompatibility and ultrasound-mediated piezocatalytic properties. In addition, the ability of these nanomaterials to disaggregate amyloid proteins, which are responsible for a range of diseases resulting from the accumulation of...

Covalent organic frameworks (COFs) are crystalline materials with intrinsic porosity that offer a wide range of potential applications spanning diverse fields. Yet, the main goal in the COF research area is to achieve the most stable thermodynamic product while simultaneously targeting the desired size and structure crucial for enabling specific fu...

Stimuli-responsive functional micro-/nanorobots (srFM/Ns) are a class of intelligent, efficient, and promising microrobots that can react to external stimuli (such as temperature, light, ultrasound, pH, ion, and magnetic field) and perform designated tasks. Through adaptive transformation into the corresponding functional forms, they can perfectly...

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely employed in biomedical fields, including targeted delivery of antitumor therapy. Conventional magnetic tumor targeting has used simple static magnetic fields (SMFs), which cause SPIONs to linearly aggregate into a long chain-like shape. Such agglomeration greatly hinders the intra...

Metachronal motions are ubiquitous in terrestrial and aquatic organisms and have attracted substantial attention in engineering for their potential applications. Hard‐magnetic soft materials are shown to provide new opportunities for metachronal wave‐modulated robotic locomotion by multi‐agent active morphing in response to external magnetic fields...

Making reliable robots that effectively operate in unstructured environments can be deceptively hard.

Magnetoelectricity enables a solid-state material to generate electricity under magnetic fields. Most magnetoelectric composites are developed through a strain-mediated route by coupling piezoelectric and magnetostrictive phases. However, the limited availability of high-performance magnetostrictive components has become a constraint for the develo...

*** Full paper available here: https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/615040/ismr_cardiac_ablation.pdf *** Cardiac arrhythmia refers to a condition of an abnormal or irregular heartbeat, which usually results in disturbed blood flow. This can lead to a reduced cardiac output and an increased risk for blood clot for...

Piezo-photocatalysis has emerged as a promising strategy to address environmental pollution and the fast-growing energy shortage. Unfortunately, current efficiencies of piezo-photocatalysts are still far from ideal, and improving their catalytic efficiency remains challenging. In this paper, we introduce oxygen vacancies (OVs) in Bi4Ti3O12 (BIT) na...

The past decade has seen an upsurge in the development of small‐scale magnetic robots for various biomedical applications. However, many of the reported designs comprise components with biocompatibility concerns. Strategies for fabricating biocompatible and degradable microrobots are required. In this study, polyvinyl alcohol (PVA)‐based magnetic h...

Magnetic continuum soft robots can actively steer their tip under an external magnetic field, enabling them to effectively navigate in complex in vivo environments and perform minimally invasive interventions. However, the geometries and functionalities of these robotic tools are limited by the inner diameter of the supporting catheter as well as t...

Magnetoelectric (ME) oxide materials can convert magnetic input into electric output and vice versa, making them excellent candidates for advanced sensing, data storage, and communication. However, their application has been limited to rigid devices due to their brittle nature. Here, flexible ME oxide composite (BaTiO3/CoFe2O4) thin film nanostruct...

The shape recovery ability of shape-memory alloys vanishes below a critical size (~50 nm), which prevents their practical applications at the nanoscale. In contrast, ferroic materials, even when scaled down to dimensions of a few nanometers, exhibit actuation strain through domain switching, though the generated strain is modest (~1%). Here, we dev...

Selective control mechanisms of microrobots have attracted significant attention from researchers. So far, selective control within multiple/swarm magnetic microrobots has been achieved with many strategies, such as utilizing locally specified magnetic fields, applying electrostatic anchoring, taking the advantages of geometry/wettability heterogen...

Detecting gait phases with wearables unobtrusively and reliably in real-time is important for clinical gait rehabilitation and early diagnosis of neurological diseases. Due to hardware limitations of microcontrollers in wearable devices (e.g., memory and computation power), reliable real-time gait phase detection on the microcontrollers remains a c...

Motion capture systems are widely accepted as ground-truth for gait analysis and are used for the validation of other gait analysis systems. To date, their reliability and limitations in manual labeling of gait events have not been studied. Objectives Evaluate manual labeling uncertainty and introduce a hybrid stride detection and gait-event estim...

Science Robotics welcomes papers demonstrating technical and scientific advances, with potential for influence beyond robotics.

*** Full paper available here: https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/588302/IROS22_3111_FI.pdf?sequence=6 *** Variable stiffness catheters typically rely on thermally induced stiffness transitions with a transition temperature above body temperature. This imposes considerable safety limitations for medical applicat...

Advanced flexible electronics and soft robotics require the development and implementation of flexible functional materials. Magnetoelectric (ME) oxide materials can convert magnetic input into electric output and vice versa, making them excellent candidates for advanced sensing, actuating, data storage, and communication. However, their applicatio...

Twin‐to‐twin transfusion syndrome (TTTS) is a severe disorder that often leads to the death of monochorionic twin fetuses, if left untreated. Current prenatal interventions to treat the condition involve the use of rigid fetoscopes for targeted laser coagulation of the vascular anastomoses. These tools are limited in their area of operation, making...

Cell therapy refers to a treatment that involves the delivery of cells or cellular material by means of injection, grafting, or implantation in order to replace damaged tissue and restore its function, or to aid the body in fighting disease. However, limitations include poor targeting delivery and low therapeutic efficacy due to low cell survival....

Electric fields have been highlighted as a smart reagent in nature's enzymatic machinery, as they can directly trigger or accelerate redox and/or non-redox chemical processes with stereo- and regio-specificity. In natural catalysis, controlled mass transport of chemical species in confined spaces is also key in facilitating the transport of reactan...

*** Full paper available here: https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/570973/Gradiometer_based_magnetic_localization_for_medical_tools_for_IEEE_T_MAG_final.pdf?sequence=1 *** Remote magnetic navigation offers various possibilities for medical interventions. Magnetic catheters can be wirelessly steered with high preci...

*** Full paper available here: https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/566922/Workspace_eMNS_TRO_final.pdf *** In remote magnetic navigation, a magnetic navigation system is used to generate magnetic fields to apply mechanical wrenches to steer a magnetic object. This technique can be applied to navigate untethered mi...

To build better machines, roboticists need to ask the right questions.

Directed transport of microcargoes is essential for living organisms as well as for applications in microrobotics, nanotechnology and biomedicine. Existing delivery technologies often suffer from low speeds, limited navigation control and dispersal by cardiovascular flows. In cell biology, these issues are largely overcome by cytoskeletal motors th...

*** Full paper available here: https://www.research-collection.ethz.ch/handle/20.500.11850/551965 *** Remote magnetic navigation offers an ideal platform for automated catheter navigation. Magnetically guided catheters show great dexterity and can reach locations that are otherwise challenging to access. By automating aspects of catheterization pr...

The use of magnetic fields and field gradients to move magnetic material and devices within the human body has a surprisingly long history. Over the past two decades, there has been renewed interest in this area with the growth of magnetic medical microrobots. In this article, we focus on the state-of-the-art and future directions for magnetically...

*** Full text available here: https://www.research-collection.ethz.ch/handle/20.500.11850/555813 *** Remote magnetic navigation is a technology used to robotically steer magnetic medical instruments, such as magnetic catheters and guidewires, for minimally invasive surgery. The ability to model and simulate the behavior of these magnetic instrumen...

The gold-standard for treating some neurovascular diseases such as ischemic stroke is an effective and minimal invasive endovascular technique. The primary instruments used are catheters and guidewires that are inserted into the vasculature through a small incision at the groin [1]. Some instruments have a curved tip allowing for easier access of d...

In the last twenty years, radiofrequency ablation of cardiac arrhythmias has increasingly become the number one therapy as it is potentially curative and negates the need for long-term medication [1], [2]. Remote magnetic navigation is a proven technique used to reduce fluoroscopy [3] and assist navigation to sites with difficult anatomic locations...

The conventional systemic administration of drugs has been utilized in medicine for centuries. However, sys- temic drug administration limits the kind of drugs and the minimally required doses for treatment inside the human body. Furthermore, directly delivering pharma- ceuticals to the location inside the body where they are needed would increase...