Application Cases

Introduction

Owing to its high‑resolution capability, the inverted microscope has become a core tool for biological and medical research. When integrated with micromanipulation technologies, it enables sophisticated manipulation and analysis of biological samples. Nevertheless, existing micromanipulation systems and tools are mostly custom‑built for specific single tasks, presenting notable functional limitations. In non‑contact manipulation, magnetic, electric, optical and fluidic force fields are widely adopted to actuate micro‑objects. However, direct application of field forces may damage biological samples, whereas indirect actuation requires micro‑robots as manipulation intermediaries. In recent years, rigid magnetically‑controlled micro‑robots (featuring large driving forces) and soft magnetically‑controlled micro‑robots (possessing programmable deformation capabilities) have attracted substantial research interest. Their fabrication mostly relies on photopolymerization for precision machining of arbitrary three‑dimensional structures.Nevertheless, magnetization and actuation of micro‑robots in current solutions generally depend on two separate magnetic‑field systems. Post‑fabrication transfer and assembly across multiple platforms result in cross‑platform workflows, long processing durations and high sample loss rates. Furthermore, the conventional combination of Helmholtz coils and Maxwell coils is difficult to integrate due to the extremely limited Z‑axis space of inverted microscopes. Accordingly, integrating in‑situ digital photopolymerization fabrication and a multimodal electromagnetic actuation system under an inverted microscope to achieve on‑site fabrication and immediate actuation of magnetically‑controlled micro‑robots, while satisfying the operational requirements for both uniform and gradient magnetic‑field modes, represents a critical research direction in this field. It addresses the bottleneck of “decoupled fabrication‑actuation” and facilitates the convenient and multi‑functional advancement of biomedical micromanipulation.

This study builds upon the classical magnetic actuation mechanisms—where uniform magnetic fields drive soft-body deformation and gradient magnetic fields drive rigid-body translation—while overcoming the inherent paradigm of conventional magnetically actuated robots, where fabrication and actuation are separated and require cross-platform transfer and assembly. By integrating a digital photopolymerization system into the optical path of an inverted microscope and embedding multi-axis pluggable iron-core electromagnetic coils into the microscope stage, it enables simultaneous generation of uniform magnetic fields (for magnetization and soft-body actuation) and gradient magnetic fields (for rigid-body actuation) within the same field of view.

The system supports in-situ fabrication and on-site actuation of two categories of magnetically actuated robots: soft robots (serpentine, centipede, and butterfly configurations) and rigid robots (Y-shaped carriers). It reduces process duration by over 50% and sample loss rate to below 10%, and breaks through the bottleneck that conventional Helmholtz-Maxwell coils cannot be integrated into inverted microscopes due to Z-axis space constraints.Rather than subverting the fundamental principles of magnetic actuation, this study provides a universal integrated system for the in-situ fabrication and multifunctional on-site actuation of magnetically actuated robots on a high-resolution microscopic platform. It represents a significant technological advancement that propels magnetically actuated robots from single-function, cross-platform operation toward multifunctional integration and in-situ practical application.

Research Direction

In-situ Digital Photopolymerization Fabrication System Under an Inverted Microscope,Compact Magnetic Actuation System with Multi-axis Pluggable Iron-core Electromagnetic Coils,Programmable Deformation Actuation of Soft Bionic Microrobots,Magnetically Actuated Micro/nanorobots.

Experimental objective

The motion of photopolymerized microrobots under an inverted microscope is controlled by multimodal magnetic fields generated by electromagnetic coils.

Testing equipment

High-precision Digital Tesla Meter,Motorized XYZ Stage,sCMOS Camera (pco. edge 4.2 LT),Voltage Amplifier (Aigtek ATA-2042),Inverted Microscope (Nikon ECLIPSE TI2-E).

Experimental process

Three ATA-2042 high-power amplifiers are connected to the output terminals of the microcontroller chip and the five coils of the electromagnetic coil system, respectively. Commands sent from the host computer are amplified by a specific factor via the amplifiers to realize control over the electromagnetic coil system, which generates magnetic fields of designated intensity and frequency through the electromagnetic effect.The high-power amplifiers are compatible with our high-resistance coils and deliver effective, timely signal response. Different amplification factors can be configured to adapt to the two operating modes: gradient magnetic field and uniform magnetic field. When placed at the center of the electromagnetic coils, the photopolymerized magnetically actuated microrobots can effectively respond to the magnetic field and achieve controlled motion.

Figure1 Experimental setup of the proposed instant tool kit. 

Figure2  experimental setup.

Experimental results

As shown in Figure 3, gradient magnetic fields and uniform magnetic fields can be effectively generated by adjusting the position of the iron core in the electromagnetic coil system in conjunction with controlling the input voltage intensity via the amplifiers. The rapid response of the amplifiers to host computer signals enables the electromagnetic coil system to flexibly regulate magnetic field modes.

Figure 4 presents a crawling multi-legged robot and a flying butterfly robot fabricated via photopolymerization. Driven by the high-frequency signals output from the amplifiers, the electromagnetic coils can rapidly vary the direction, frequency and intensity of the magnetic field. For the crawling robot, multi-directional coordinated control of its multiple legs is realized, supporting crawling locomotion as well as posture and orientation adjustment. The butterfly robot can achieve wing-flapping motion accordingly.

Figure3 Multimodal magnetic fields generated by multiple electromagnetic coils with withdrawable iron cores. (a) Insertion of the iron cores to

generate a gradient magnetic field. (b) Simulation of the generated gradient magnetic fields with big intensity variations and dense magnetic field

isolines under an applied voltage of 25V. (c) Measurement of the generated gradient magnetic fields under various applied voltages.(d)Withdrawal of iron cores to generate a uniform magnetic field. (e) Simulation of the generated uniform magnetic fields with small intensity variations and sparse magnetic field isolines under an applied voltage of 25 V. (f) Measurement of the generated uniform magnetic fields under various applied voltages and gaps. (g) Z-axis coil to generate the uniform magnetic field. (h) Simulation of the generated uniform magnetic fields with small intensity variations and sparse magnetic field isolines in the X–Z plane under an applied voltage of 75 V. (i) Simulation of magnetic field intensity distribution along the Z-axis of the generated uniform magnetic fields under various applied voltages.

Figure4  (c) Biomimetic centipede. (d) Biomimetic butterfly. The scale bar is 200 µm.

The effectiveness of the amplifier in this experiment

1. Amplify the low-voltage control signals output by the MCU into high-voltage/high-current signals sufficient to drive the electromagnetic coils.

2. Adjust the coil current by varying the amplification factor, thereby precisely controlling the intensity of uniform and gradient magnetic fields.

3. Respond rapidly to host computer commands to realize real-time dynamic switching of magnetic field frequency and direction.

4. Provide independent actuation for multi-axis (X, Y, Z) electromagnetic coils, supporting flexible regulation of spatial magnetic fields.

5. Work in conjunction with high-impedance coils to ensure timely and effective signal transmission free from delay and distortion.

Application fields

Biomedical Single-Cell Manipulation,Smart Valves and Switches in Microfluidic Chips,Targeted Drug Delivery and Minimally Invasive Surgery,Bionic Soft Robots,Microassembly and Micro/Nano Manufacturing.