Soft robotics represents a paradigm shift in how we design and deploy machines. Unlike their rigid, jointed predecessors, soft robots are built from compliant materials—silicones, hydrogels, elastomers—that allow them to bend, stretch, twist, and squeeze in ways that mimic biological organisms. This inherent flexibility makes them ideal for operating in cluttered, fragile, or unpredictable environments. However, the very compliance that gives soft robots their advantage also presents a fundamental control challenge: how do you precisely actuate and steer a robot that has no rigid links or traditional motors?

Enter magnetic fields. Over the past decade, the use of magnetic actuation has emerged as one of the most promising solutions for remotely controlling soft robots. By embedding magnetic particles directly into the robot’s body, researchers can apply external magnetic fields to deform the robot, generate locomotion, and even perform complex tasks—all without any physical tether or internal power source. This approach offers unparalleled precision, safety, and versatility, opening doors to applications ranging from targeted drug delivery to deep-sea exploration. In this article, we dive deep into the physics, engineering, and future potential of magnetically actuated soft robots.

Understanding Magnetic Actuation in Soft Robotics

At its core, magnetic actuation relies on the interaction between an externally applied magnetic field and magnetic materials embedded within the soft robot. The principle is straightforward: when a magnetic material is placed in a magnetic field, it experiences a torque (rotation) and/or a translational force. In a soft robot, these forces cause the robot’s body to deform, which can be harnessed for gripping, crawling, swimming, or rolling.

The Role of Magnetic Materials

The choice of magnetic filler is critical. Common materials include neodymium-iron-boron (NdFeB) microparticles, which have high remanent magnetization, or superparamagnetic iron oxide nanoparticles (SPIONs) that respond strongly to fields but are non-magnetic in the absence of an external stimulus. The particles are typically dispersed in a polymer matrix during fabrication. The resulting composite can be magnetized in a specific pattern (e.g., a programmed magnetization profile) so that when an external field is applied, the robot deforms in a predetermined way.

Generating the Magnetic Fields

External magnetic fields can be produced by permanent magnets or electromagnets. For lab-scale experiments and clinical prototypes, systems of multiple electromagnet coils arranged around the workspace are common. These coils can generate fields of up to 0.1–1 T and can be rapidly switched or rotated to produce dynamic sequences. Some advanced setups use eight-coil configurations (e.g., OctoMag, MiniMag) that allow full six-degree-of-freedom control of both the field direction and magnitude. Permanent magnets offer simplicity and strong fields but lack the dynamic control of electromagnets.

Actuation Modes

Soft robots can be actuated in several distinct ways using magnetic fields:

  • Bending and twisting: A magnetized beam or sheet bends when a field is applied perpendicular to its magnetization direction.
  • Snap-through buckling: Fast transitions between bistable shapes, allowing fast jumping or grasping.
  • Undulatory locomotion: Sequential bending waves propagate along the body, similar to a worm or sperm cell.
  • Rolling and tumbling: Spherical or cylindrical soft bodies roll under rotating fields.

Advantages of Magnetic Actuation for Soft Robots

Compared to other actuation methods—such as pneumatic, hydraulic, thermal, or electrostatic—magnetic actuation offers unique benefits that make it especially attractive for remote and delicate applications.

True Remote and Tetherless Control

Because magnetic fields pass through most non-magnetic materials (air, water, tissue, plastic) with little attenuation, the robot can be driven from a distance. There is no need for wires, tubes, or batteries onboard. This eliminates the size and weight constraints of power sources and enables miniaturization down to micrometer scales.

High Precision and Programmable Motion

By carefully shaping the magnetization profile of the robot and tuning the external field, engineers can achieve highly repeatable and accurate motions. For example, a magnetically programmed “soft crawler” can be made to follow a specific path or grip objects with controlled force. The precision can reach sub-millimeter levels, suitable for micromanipulation.

Non-Invasive and Safe for Biomedical Use

Magnetic fields at the strengths used in soft robotics (typically 0.1–1 T) are generally considered safe for biological tissues. Unlike electrical actuation, there is no need for contacts or implants that could cause trauma. This makes magnetic soft robots ideal candidates for minimally invasive surgery, drug delivery, and diagnostic imaging.

Multi-Modal Capabilities

A single magnetic field can produce multiple deformation modes: bending, twisting, stretching, and even shape locking. By varying the field amplitude, frequency, and direction, a soft robot can switch between different gaits or functions without mechanical reconfiguration.

Key Applications of Magnetically Actuated Soft Robots

The unique characteristics of magnetic soft robots have led to their exploration in a wide array of fields. Here we highlight the most impactful current and emerging applications.

Biomedical Devices

This is perhaps the most active area of research. Magnetically steered soft robots can navigate through the body’s narrow, tortuous pathways to deliver therapies or perform procedures. Examples include:

  • Targeted drug delivery: A soft microrobot loaded with chemotherapeutic agents can be guided via an external magnetic field to a tumor site. The robot then releases its payload in response to a specific pH or temperature trigger. Researchers at ETH Zurich have demonstrated a hydrogel-based soft robot that can swim through blood vessels (Nature Communications, 2019).
  • Minimally invasive surgery: Magnetic catheters and endoscopes can be steered with greater flexibility than conventional tools. A soft robotic manipulator with a magnetized tip has been used for retinal surgery, where precision is paramount (Science Robotics, 2019).
  • Micro-grippers: Millimeter-scale soft grippers that close in response to a magnetic field can retrieve tissue samples or foreign objects without damaging surrounding tissue.

Search and Rescue

Soft robots that can squeeze through gaps and crawl over rubble are attractive for disaster scenarios. Magnetic control allows a single operator to guide them from a safe distance, while the robot’s soft body avoids damaging victims or structures. Researchers at Harvard’s Wyss Institute have developed a magnetically actuated soft robot that can crawl and jump over obstacles (Wyss Institute, 2020).

Industrial Automation

In manufacturing and logistics, soft grippers are used to handle delicate items such as food, glassware, or electronic components. Magnetic actuation provides a gentle yet firm grip, and the absence of pneumatic tubes simplifies the system. Moreover, magnetic fields can be synchronized with conveyor systems for high-speed sorting.

Environmental Monitoring and Exploration

Magnetically controlled soft robots can traverse complex terrains—sandy deserts, muddy wetlands, underwater reefs—without motors or tracks. They can be deployed for water sampling, pollution mapping, or inspection of pipelines. Their resilience and low cost make them ideal for environmental sensing networks.

Challenges Facing Magnetic Soft Robots

Despite the promise, several technical hurdles must be overcome before magnetic soft robots become commonplace.

Limited Magnetic Field Penetration Depth

Although magnetic fields pass through most non-magnetic media, their strength decays with distance. For a robot deep inside the body (e.g., in the stomach or colon), the field from an external coil may be too weak to produce useful forces. This limitation restricts the size and depth of the workspace. Solutions under investigation include using stronger local coils (e.g., inserted via endoscope) or miniaturized onboard magnets that amplify the external field.

Material Challenges

The composite materials used must be biocompatible, flexible, and durable. High concentrations of magnetic particles can stiffen the elastomer, reducing compliance. Conversely, too few particles reduce actuation force. Researchers are exploring new particle shapes (rods, disks) and surface coatings to improve dispersion and mechanical properties. Additionally, the magnetization can degrade over time, especially if the robot is subjected to repeated large deformations.

Control Complexity

Soft robots are inherently more difficult to model than rigid ones because they exhibit nonlinear deformation, hysteresis, and viscoelasticity. Precise magnetic control requires real-time feedback of the robot’s shape and position, which may rely on imaging modalities (X-ray, ultrasound, MRI). Closed-loop control algorithms that fuse sensor data with magnetic field computation are still an active area of research.

Miniaturization and Power

For true microrobots (sub-millimeter), generating a strong enough field gradient to propel them becomes more difficult. The robot’s own magnetic moment scales with volume, while the magnetic force scales with the gradient. At small scales, Brownian motion and viscous drag dominate. Nevertheless, teams have demonstrated bacteria-sized magnetic swimmers that can move through viscous fluids (Science Robotics, 2018).

Future Directions and Emerging Innovations

The field of magnetic soft robotics is moving fast. Several exciting developments point to what the next decade may bring.

Advanced Magnetic Composites

New materials such as liquid metal–magnetic particle hybrids, shape-memory magnetic polymers, and stretchable magnetic skins are being tested. These could enable robots that change stiffness on demand or self-heal after damage.

Multi-Field Actuation Hybrids

Combining magnetic fields with other stimuli—light, heat, pH, ultrasound—can provide orthogonal control. For example, a soft robot can be magnetically steered to a target, then triggered to release a drug by a near-infrared laser. This multi-modal approach increases functionality.

AI and Machine Learning for Control

Deep reinforcement learning is being applied to discover optimal magnetic field sequences for complex gaits or tasks. Instead of manually programming a crawling pattern, an algorithm can learn it through trial and error, adapting to different environments. Such approaches could make magnetic soft robots truly autonomous.

Clinical Translation

The first human trials of magnetically guided soft capsules for gastrointestinal endoscopy are already underway. Companies like Endostart and MagBot are developing steerable soft robots for colonoscopy and drug delivery. Regulatory approvals and safety studies will be critical before widespread use.

Scalable Manufacturing

Techniques like 3D printing with magnetic filaments, injection molding of magnetized elastomers, and roll-to-roll fabrication are lowering production costs. This paves the way for disposable soft robots for one-time medical procedures or environmental clearance missions.

Conclusion

Magnetic actuation has unlocked a new dimension in soft robotics. It provides the ability to remotely control compliant machines with high precision, safety, and versatility. From navigating the bloodstream to wrangling rubble, these robots are poised to address some of the most demanding challenges in medicine, industry, and exploration. While obstacles remain—limited penetration depth, material optimization, and control complexities—ongoing research in advanced materials, AI-driven control, and hybrid actuation is rapidly closing the gap.

The combination of magnetic fields and soft materials represents a convergence of physics, materials science, and robotics. As this technology matures, we can expect to see soft robots that are not only flexible but also intelligent, responsive, and truly untethered. The era of magnetic soft robotics is just beginning.