Research Philosophy: Mastering Chirality as a Design Principle

Our research focuses on the bottom-up construction of functional soft materials through supramolecular self-assembly. A central theme is the exploitation of molecular chirality—a fundamental geometric property where a molecule cannot be superimposed on its mirror image—to control the assembly process across multiple length scales, from nanometers to micrometers and beyond. We view molecular chirality not merely as a structural feature, but as a powerful information code that can be precisely written into molecular building blocks, transmitted and amplified through supramolecular self-assembly, and ultimately expressed as programmable macroscopic functions. We specifically engineer C₂-symmetric chiral gelators, molecules with a unique two-fold symmetric axis of chirality, to create hydrogels with precisely defined hierarchical structures and emergent functions.

Foundational Achievement: Molecular Design & Precision Chirality Control

The key to our approach is the rational design of C₂-symmetric building blocks. This symmetry enforces a specific spatial arrangement during assembly, leading to highly ordered and predictable one-dimensional growth into nanofibers. The chirality embedded in the side chains or core is not only preserved but amplified through the assembly process, translating molecular information into supramolecular chirality.

Distinctive Features and Advantages

Our C₂-symmetric chiral hydrogels exhibit remarkable properties that distinguish them from conventional gels:

• Precise Chirality Control: The inherent C₂ symmetry allows for strict control over the supramolecular helical sense, enabling the creation of purely left- or right-handed gel networks.
• Stimuli-Responsiveness: The gels can dynamically respond to external cues such as pH, temperature, ions, or light, leading to reversible sol-gel transitions or chiral switching.
• Nanoscale Order in a Hydrated 3D Matrix: They provide a unique, water-rich environment with a highly ordered nanostructure, mimicking the essential features of the extracellular matrix (ECM).
• Circularly Polarized Luminescence (CPL): By doping with or covalently attaching luminophores, the chiral scaffolds can transfer their handedness to emitted light, generating CPL—a property valuable for advanced optical devices and encryption.

Research Thrust I: Advanced Chiral Modulation Strategies

Beyond static chirality, we have developed a toolbox for dynamic chiral control, making our materials responsive and adaptive.

• Stimuli-Responsive Chiral Switching

A: pH-Triggered Inversion: Incorporating pH-sensitive groups (e.g., carboxylates, amines) allows the protonation state to modulate intermolecular interactions, leading to reversible helical sense inversion. This mimics the dynamic chirality found in some biological systems.

B: Photo-Driven Chirality Modulation: Using azobenzene or other photo-switches as part of the C₂-symmetric core enables light-induced trans-cis isomerization. This changes the molecular shape and packing, dynamically altering the supramolecular chirality or even triggering gel-sol transitions.

C: Ion-Responsive Handedness Selection: Specific metal ions (e.g., Cu²⁺, Zn²⁺) can coordinate with ligand sites on the gelator, forming chiral complexes that nucleate assembly with a handedness different from the metal-free system, enabling ion-selective chiral outputs.

• Kinetic Pathway Control for Metastable Chirality

We have demonstrated that the assembly kinetics—controlled by cooling rate, ultrasound, or seeding—can trap the system in metastable chiral states. This provides a way to access multiple chiral architectures from a single molecular building block, expanding the structural and functional landscape.

• Co-Assembly for Chirality Fine-Tuning

By co-assembling our C₂-symmetric gelators with other chiral/achiral additives (e.g., amino acids, drugs, chiral polymers), we can finely tune the expression of supramolecular chirality. The additive can act as a "chiral dopant," perturbing the assembly to subtly shift helical pitch or stability, or even induce a complete handedness switch if its chiral influence is strong enough. This is a powerful method for creating chiral gradients or patterns.

Research Thrust II: Functional Applications Enabled by Chirality Control

Our work explores several frontiers where these intelligent gels can have transformative impacts, unlocking the unique applications of chiral materials.

• 3D Cell Culture and Chiral Biology

The hydrogel's nanoarchitecture and chirality significantly influence cell behavior—adhesion, proliferation, migration, and differentiation. We investigate "chiral recognition" at the cell-material interface, exploring how left- vs. right-handed matrices can differentially interact with cells, offering new insights in tissue engineering and regenerative medicine.

• Chiral Optics & Information Storage

The strong and switchable chiral signals (CD/CPL) of our materials make them candidates for chiroptical devices and security features. We have created gels whose CPL color or intensity changes reversibly with a stimulus, offering potential for anti-counterfeiting tags or optical memory elements with multiple states defined by chiral configuration.

• Enantioselective Adsorption and Separation

Our chiral hydrogels act as selective matrices for resolving racemic mixtures. The handedness of the network can preferentially adsorb, template the crystallization of, or retard the diffusion of one enantiomer over its mirror image. This enables their application in enantiomeric purification (resolution), a critical challenge in pharmaceutical synthesis, and in the design of chiral sensors.

• Smart Chiral Actuators and Soft Robotics

By patterning chiral regions or creating gradients, we fabricate chiral constructs that undergo predictable, directional deformation. Upon swelling or stimulus response, these actuators twist, coil, or bend in a manner dictated by their programmed chiral architecture, enabling the design of soft grippers and micro-swimmers. This "chiral actuation" paves the way for soft robots, microfluidic valves, and artificial muscles.

Future Vision: Towards Intelligent Chiral Systems

We are pushing the boundaries of this field by:

• Developing dynamic, reconfigurable chiral systems with life-like adaptivity.
• Integrating multi-chirality for more complex information coding and functions.
• Exploring therapeutic applications, such as chiral drug delivery systems or antimicrobial chiral surfaces.
• Coupling chirality with electronic or ionic conductivity for chiral electroactive materials.
• Exploring how chiral signals can be transmitted between different material components or even to biological entities.

In summary, the research on C₂-symmetric chiral supramolecular hydrogels establishes a powerful paradigm for creating bio-inspired, intelligent soft materials. By developing sophisticated strategies to program, modulate, and switch chirality at will, we transform this fundamental geometric property into a versatile toolkit for creating the next generation of smart, adaptive, and bio-inspired functional materials. The research opens new avenues in nanotechnology, biomedicine, and beyond, bridging the gap between fundamental supramolecular chemistry and advanced functional applications.