Soft Intelligent Materials Laboratory, Prof. Renee Zhao
SIMLab at Stanford: Smart materials, structures, and devices
Prof. Ruike Renee Zhao leads the Soft Intelligent Materials Laboratory (SIMLab) at Stanford.
SIMLab focuses on interdisciplinary research, with the members’ backgrounds in Solid Mechanics, Mechanical Engineering, Materials Science, and Electrical Engineering.
Smart materials, or active materials, show large and programmable shape morphing in response to external stimuli, such as heat, light, pH, or magnetic field in a controllable manner. The shape manipulation capabilities and integrated functionalities distinguish smart materials from conventional rigid materials, finding diverse applications in soft actuators, soft robotics, flexible electronics, morphing structures, and biomedical devices. There is an increasing demand on the fundamental understanding of smart material systems when exploiting their applications in different engineering fields.
SIMLab aims at addressing challenges in development and application of smart materials through interdisciplinary studies utilizing analytical, numerical, and experimental tools. Research in SIMLab focuses on several aspects including: advances of various types of smart materials; origami and shape morphing metamaterials with engineered properties; 3D printing of smart materials/structures; biomedical devices based on smart materials/structures.
1. Smart Materials
Advances in smart materials lay the foundation for the development of soft and intelligent systems. Based on the design, smart materials behave differently upon external stimuli such as stress, temperature, light, and electric or magnetic fields. We study a wide range of materials, especially polymers, including magnetic soft materials (MSMs), shape memory polymers (SMPs), dynamic polymers (DPs), and liquid crystal elastomers (LCEs). MSMs are composite materials which consist of magnetic particles embedded in an inactive polymer matrix, exhibiting merits of untethered, fast, and reversible morphing under precise magnetic field control. Dr. Qiji Ze, whose background is in Electrical Engineering, has established electromagnetic actuation systems in SIMLab for the precise control of MSMs. Combining magnetic particles with other active polymer matrices, for example SMPs that show stiffness change under heating, Qiji and others develop magnetic shape memory polymers (MSMPs) with integrated multifunctionalities. PhD student Yilong Chang, master student Victor Maurin, and undergraduate student Sophie Leanza are also actively studying soft actuators and sensors based on LCEs and DPs. Additionally, Dr. Yucan Peng is using smart materials to pursue novel battery designs with self-healing capability.
2. Origami and shape morphing metamaterials
The structural design of smart material systems enables more complex shape morphing, like origami folding. Origami, the ancient art of paper folding, allows the reshaping of flat sheets into intricate 3D structures. Origami-based reconfigurable systems enable various deformations and motions that can be applied in morphing structures, soft robotics, and biomedical devices. For example, inspired by the soft-bodied cephalopod biosystem, we engineer compliant origami robotic arms to achieve multimodal deformations that integrate stretching, folding, omnidirectional bending, and twisting. We also demonstrate an alternative folding strategy called ring origami. Ring origami uses a snap-folding mechanism triggered by the buckling instability of rods under either bending or twisting load. It is demonstrated that the snap-through instability leads to a self-guided folding behavior while showing high packing abilities for rings with different geometries. Dr. Lu Lu, whose background is in Solid Mechanics, is working on theoretical modeling of various deformable systems, including paper-folding origami and foldable rings. Sophie Leanza, PhD student Shuai Wu, and master student Jize Dai are working on finite element simulation-guided ring design for foldable electronics.Metamaterials, or materials exhibiting properties not found in nature, often consist of specifically designed periodic patterns and are capable of tailorable mechanical, acoustic, optical, or electromagnetic properties. Reconfigurable metamaterials, also called active metamaterials, facilitate more versatile and programmable use, as they possess actively tunable patterns and/or physical properties. PhD students Shuai Wu, Chunping Ma, and Yilong Chang are developing metamaterials that actively tune the deformations and their physical properties. They also explore combining mechanics-guided design with optimization algorithms and machine learning to create active metamaterials with desired properties.
3. 3D printing
Advances in three-dimensional (3D) printing technology allow for the fabrication of smart materials, and we study both single- and multi-material printing, which further enhances the structural programmability of smart materials. Victor Maurin and Sophie Leanza are currently working on 3D printing for multi-material systems that show response to coupled thermal and magnetic stimuli, realizing various deformation modes in one structure. With the large design space of 3D printed smart materials (MSMs, MSMPs, LCEs, etc.), guidance for rational 3D printing is essential to effectively engineer the material composition, distribution, or combination of multiple materials. SIMLab relies on the mechanics of reconfigurable systems through methods of material constitutive law development, theoretical prediction, or finite element simulation of shape morphing structures.
4. Biomedical devices
Based on smart materials and structures, SIMLab members aim to push the boundary of soft and intelligent materials for next generation devices in biomedical applications such as drug delivery robots, biomedical tubes, insulin pumps, non-invasive surgery tools for blood clot, kidney stone, and plaque removal. Currently, Dr. Qiji Ze and Yilong Chang are working towards creating millimeter scale magnetic soft robots that actively sense, decide, and react to external environments. Working with Yilong Chang, undergraduate student Maya Grant is working on intubation tubes for infants. Together with Jize Dai, undergraduate student Shelby Scott is finding solutions for miniaturized insulin pumps which utilize magnetically responsive materials. PhD students Six Skov, Ethan Darwin, Yilong Chang, and Shuai Wu are developing biomedical tools for effectively removing blood clots in blood vessels, and undergraduate Grace Pan is developing biomedical tools for the treatment of kidney stones.