Publications

Soft magnetic miniature devices are crucial for applications in minimally invasive medicine, soft electronics, and robotics. While substantial progress has been made, current magnetic programming techniques are inherently tied to template-based and sequential fabrication processes. These processes limit scalability, precision, and programmability. Here, we present a template-free, integrative strategy that leverages interlayer stress-induced 3D shape morphing in xerogel-PDMS bilayer materials triggered by temperature variations. This process induces preprogrammed deformation and fixes the 3D structure via interlayer stress and solid–liquid phase transition. It is akin to an insect encased in amber, resulting in a soft machine with precisely tailored magnetic domains upon saturated magnetization. The approach eliminates the need for predesigned molds, which offers scalable, template-free programmable magnetization, reducing time and labor costs. It paves the way for advanced multiscale and programmable soft magnetic devices. 

Han, J.#, Wang, S.#, Zheng Z.*, Sitti, M.*, Dong Li. et al. "Template-free 3D programmable magnetization of soft millirobots induced by interlayer stress", Proceedings of the National Academy of Sciences (PNAS), 2025, 122 (23) e2426846122

This paper introduces a single-step methodology for crafting soft millirobots capable of intricate multistep shape morphing in response to independently decoupled environmental stimuli. The unique feature of decoupling shape morphing empowers the independent programming of each transformation step, resulting in a substantial augmentation of both degrees of freedom and overall system functionality. Our approach facilitates the realization of multistep shape morphing, giving rise to a myriad of intricate three-dimensional (3D) structures, encompassing biomimetic shapes, expressive gestures, kirigami architectures, pop-ups, and bistable configurations. This technique embodies a versatile paradigm for crafting multifunctional and adaptable 3D devices, applicable across a diverse spectrum of fields. 

Zheng Z.#, Han, J.#, Sitti, M.*, et al. "Single-step precision programming of decoupled multiresponsive soft millirobots", Proceedings of the National Academy of Sciences (PNAS), 2024, 121 (13) e2320386121

The ability to sense environmental cues encoded in fluid flows could enable intelligent behaviors of artificial cilia for versatile applications such as aquatic environmental monitoring and exploration. Our proposed actuation-enhanced sensing mechanism and sensor-integrated cilium (SIC) allow for the ability of recovering environmental information such as fluid apparent viscosity, environment boundaries, and fluid flow speed with a reconfigurable sensitivity and sensing range, all by actively interacting with the fluidic environments. By incorporating the actuation-enhanced sensing mechanism, our demonstrated artificial cilia devices are promising for enabling sensing complex and dynamic cues in fluidic environments, which paves the way for developing the next generation of soft robots and devices with enhanced environmental awareness and adaptation for diverse fluidic and environmental applications.

Han, J.#, Dong, X., Sitti, M.*, et al. "Actuation-enhanced multifunctional sensing and information recognition by magnetic artificial cilia arrays", Proceedings of the National Academy of Sciences (PNAS), 2023, 120 (42) e2308301120

To navigate in complex and unstructured real-world environments, soft miniature robots need to possess multiple functions, including autonomous environmental sensing, self-adaptation, and multimodal locomotion. However, to achieve multifunctionality, artificial soft robots should respond to multiple stimuli, which can be achieved by multimaterial integration using facile and flexible fabrication methods. Here, a multimaterial integration strategy for fabricating soft millirobots that uses electrodeposition to integrate two inherently non-adherable materials, superhydrophilic hydrogels and superhydrophobic elastomers, together via gel roots is proposed. This approach enables the authors to electrodeposit sodium alginate hydrogel onto a laser-induced graphene-coated elastomer, which can then be laser cut into various shapes to function as multi-stimuli-responsive soft robots (MSRs). Each MSR can respond to six different stimuli to autonomously transform their shapes, and mimic flowers, vines, mimosas, and flytraps. It is demonstrated that MSRs can climb slopes, switch locomotion modes, self-adapt between air-liquid environments, and transport cargo between different environments. This multimaterial integration strategy enables creating untethered soft millirobots that have multifunctionality, such as environmental sensing, self-propulsion, and self-adaptation, paving the way for their future operation in complex real-world environments.

Zheng, Z.#, Han, J.#, Demir, S. O., Sitti, M.*, et al. "Electrodeposited Superhydrophilic-Superhydrophobic Composites for Untethered Multi-Stimuli-Responsive Soft Millirobots." Adv. Sci. 2023, 2302409.

为解决传统水下机器人功耗大、噪声大、机电特征易被探测的缺点,受河鲀应激防御时体型变化的启发,设计并制造了一种基于液气相变驱动的柔性水下悬停机器人（简称悬停机器人）。机器人基体由柔性硅橡胶材料制成,内部预设一腔体,腔体内封装低沸点驱动液体（3MTM NovecTM7000,沸点35℃）,通过加热驱动液体使其发生液气相变,作用在内腔壁面上的饱和蒸气压使悬停机器人的体积发生变化从而改变悬停机器人的浮力;通过控制驱动温度实现悬停机器人的上浮下潜运动与定深悬停。实验表明:悬停机器人在自封装15mL驱动液体时的驱动温度范围为50～100℃,最大可提供约为自重1.95倍的浮力;在驱动温度为53℃时,可实现定深悬停;在驱动温度范围内,浮力测量值误差小于5%。基于液气相变驱动的柔性水下悬停机器人回避了传统的机电驱动传动,自带工质,尺寸小质量轻,适合水下复杂环境作业;工作功耗小,驱动过程无噪声。

张鸿健，韩捷，蒋维涛，等。西安交通大学学报. 2021,55(02)

There is a growing interest in the design and fabrication of small-scale soft actuators and robotics, especially the realization of functionalities mimicking biological systems with biomimetic motions in response to external stimuli. However, the mobility and self-weight are still the critical challenges for further improvement and broader application of soft actuators. It is attractive to develop untethered and ultra-light small-scale robotics by integrating the actuators and drivers while achieving the ability to respond to external stimuli. Inspired by the spiders that rely on electrostatic forces in the environment to stay airborne by their ballooning silk, a positively charged fiber-paper structure-based soft actuator is proposed. Utilizing electrospinning of tetraethyl orthosilicate (TEOS) solution, this ultra-light soft actuator can realize the movement of bending and high-frequency vibration with the stimuli of electrostatic force in the electric field. Programmable motions, i.e., continuous bending with a series of angles, variable frequency vibration, can be realized by regulating the external electric field. The 3D fluffy structure of the silica micro-nanofibers and the paper-based structure endow the soft actuator with ultra-lightweight and excellent flexibility. The untethered, ultra-light soft actuator suggests a feasible approach to develop ultra-light, soft and autonomous robotics and holds promise in reconnaissance and environmental detection.

Han, Jie, et al. "Untethered, ultra-light soft actuator based on positively charged 3D fluffy silica micro-nanofibers by electrospinning." Journal of Materials Science 55.27 (2020): 12789-12800.