Current Projects

Halftone-Enabled 4D Printing of Stimulus-Reconfigurable Binary Domains for Synthetic Smart Skins

Personnel: Haoqing Yang, Haotian Li, and Moonsung Park (Ph.D. students)

We develop smart soft “skins” capable of fine-tuning versatile material properties and responsive behaviors, such as optical, mechanical, iontronic, and capacitive characteristics, as well as reconfigurable texture and shape morphing in response to stimulus (e.g., heat, light, force). To achieve this, we introduce a 4D printing technique that creates halftone patterning to control multiple dynamic features over time. Through spatially control of photo-polymerization, we encode designed features into our synthetic smart “skins,” demonstrating promising potential for applications in graphic information encryption and decryption, adaptable camouflage, self-powered sensing, and more. 

H. Yang, H. Li, J. Zhang, T. Liu,  H. J Qi*, and H. Sun*, "Halftone-Encoded 4D Printing of Stimulus-Reconfigurable Binary Domains for Cephalopod-Inspired Synthetic Smart Skins" Nature Communications, 2025, 16, 9931 . 

4D Printing of Shape-Morphing Soft Materials​

Personnel: Haoqing Yang,  Haotian Li and Moonsung Park  (Ph.D. student)

We develop a 4D printing approach to program two-dimensional (2D) hydrogel films for transformation into targeted three-dimensional (3D) shapes. For example, to spatiotemporally encode growth functions (η) into 2D films, we implement a gradient design using concentric circles. This design features rings of low-shrinking domains (under high exposure) encircled by high-shrinking domains (under low exposure), as shown by the spatial distribution of exposure times (Figure). These programmed in-plane dimensional changes drive the transformation of 2D films into 3D caps with precisely controlled Gaussian curvatures via out-of-plane buckling.    

H. Yang, T. Liu, L, Jin, Y. Huang*, X. Duan*, and H. Sun*, "Tailoring Smart Hydrogels Through Manipulation of Heterogeneous Subdomains," Nature Communications, 2024, 15, 9268.

Spatiotemporal Control of Multiscale Heterogeneities to Tailor Mechanical Properties​

Personnel: Haoqing Yang, Haotian Li  (Ph.D. students)

The tissues in soft living organisms feature meticulously arranged cellular units that are mechanically intertwined with their neighbors, exerting mutual forces and interacting with their environment. The characteristics of these cellular unit building blocks, which shape both local and global features, offer invaluable inspiration for designing synthetic soft materials. In our research, we develop synthetic smart hydrogels featuring stiff, cellular-like domains to customize their mechanical properties. Specifically, by spatiotemporal control of photo-polymerization via dynamic light projection grayscale lithography, our approach enables the regulation of multiscale heterogeneities, spanning from molecular-level dual crosslinked networks, meso- to macro-scale cellular units with localized heterogeneous subdomains, to macro-scale integrations with multiple “phases,” resulting in structural complexities across hierarchical scales (Figure). Unlike previous approaches that incorporate rigid inclusions into soft matrices to tailor material properties, our method manipulates the localization, integration, and interaction of subdomain building blocks within the soft film, allowing for extensive tuning of both local and global behaviors. This represents a new strategy for designing synthetic hydrogels. ​

H. Yang, T. Liu, L, Jin, Y. Huang*, X. Duan*, and H. Sun*, "Tailoring Smart Hydrogels Through Manipulation of Heterogeneous Subdomains," Nature Communications, 2024, 15, 9268.

Designing Bio-Inspired Interfaces and Heterogeneities in Smart Materials for Customized Actuation Behaviors​

Personnel: Haotian Li (Ph.D. student)

Natural materials are often intricate composites, endowed with unique and sometimes contradictory properties that surpass the performance of their individual components. Achieving this level of synergy in synthetic materials, however, remains a substantial challenge, with the underlying mechanisms not yet fully understood. To address this, we introduce a grayscale stereolithography-enabled printing approach to fabricate shape memory polymers (SMPs) with bio-inspired interfaces. These localized transition interfaces smooth abrupt variations between heterogeneous domains in SMPs, promoting effective integration of dissimilar features to achieve tailored mechanical and thermoresponsive behaviors. The heterogeneous mechanical features are visualized and validated through real-time full-field strain mapping using digital image correlation (DIC) analysis. Our strategy, characterized by the manipulation of heterogeneous domains and their transition interfaces, pioneers a new direction for designing and fabricating intelligent materials and advanced actuation devices.​

Z. Zhao, H. Yang, M. Li, C. Gudi, K. Kanumuru, R. Voigt, O. Babaniyi, T. Liu, Y. Chen*, and H. Sun*,"Engineering Heterogeneous Domains and Interfaces in Shape Memory Fibers for Tunable Responsive Behaviors," Chemical Engineering Journal, 2024, 480, 147936.