Qing Zhang

All Publications

• Flow-induced periodic chiral structures in an achiral nematic liquid crystal. Nature communications Zhang, Q., Wang, W., Zhou, S., Zhang, R., Bischofberger, I. 2024; 15 (1): 7

  Abstract

  Supramolecular chirality typically originates from either chiral molecular building blocks or external chiral stimuli. Generating chirality in achiral systems in the absence of a chiral input, however, is non-trivial and necessitates spontaneous mirror symmetry breaking. Achiral nematic lyotropic chromonic liquid crystals have been reported to break mirror symmetry under strong surface or geometric constraints. Here we describe a previously unrecognised mechanism for creating chiral structures by subjecting the material to a pressure-driven flow in a microfluidic cell. The chirality arises from a periodic double-twist configuration of the liquid crystal and manifests as a striking stripe pattern. We show that the mirror symmetry breaking is triggered at regions of flow-induced biaxial-splay configurations of the director field, which are unstable to small perturbations and evolve into lower energy structures. The simplicity of this unique pathway to mirror symmetry breaking can shed light on the requirements for forming macroscopic chiral structures.

  View details for DOI 10.1038/s41467-023-43978-6

  View details for PubMedID 38191525

  View details for PubMedCentralID PMC10774319

• Dendritic patterns from shear-enhanced anisotropy in nematic liquid crystals. Science advances Zhang, Q., Zhou, S., Zhang, R., Bischofberger, I. 2023; 9 (2): eabq6820

  Abstract

  Controlling the growth morphology of fluid instabilities is challenging because of their self-amplified and nonlinear growth. The viscous fingering instability, which arises when a less viscous fluid displaces a more viscous one, transitions from exhibiting dense-branching growth characterized by repeated tip splitting of the growing fingers to dendritic growth characterized by stable tips in the presence of anisotropy. We controllably induce such a morphology transition by shear-enhancing the anisotropy of nematic liquid crystal solutions. For fast enough flow induced by the finger growth, the intrinsic tumbling behavior of lyotropic chromonic liquid crystals can be suppressed, which results in a flow alignment of the material. This microscopic change in the director field occurs as the viscous torque from the shear flow becomes dominant over the elastic torque from the nematic potential and macroscopically enhances the liquid crystal anisotropy to induce the transition to dendritic growth.

  View details for DOI 10.1126/sciadv.abq6820

  View details for PubMedID 36638169

  View details for PubMedCentralID PMC9839321

• Editorial: First Annual APS DSOFT Gallery of Soft Matter. Physical review. E Shishkov, O., Blonder, A., Gowen, S., Jones, T. J., Jouanlanne, M., Zhang, Q., Del Gado, E., Bischofberger, I. 2022; 106 (5-1): 050001

  View details for DOI 10.1103/PhysRevE.106.050001

  View details for PubMedID 36559464

• Single-Shot Quantitative Polarization Imaging of Complex Birefringent Structure Dynamics. ACS photonics Ge, B., Zhang, Q., Zhang, R., Lin, J. T., Tseng, P. H., Chang, C. W., Dong, C. Y., Zhou, R., Yaqoob, Z., Bischofberger, I., So, P. T. 2021; 8 (12): 3440-3447

  Abstract

  Polarization light microscopes are powerful tools for probing molecular order and orientation in birefringent materials. While a number of polarization microscopy techniques are available to access steady-state properties of birefringent samples, quantitative measurements of the molecular orientation dynamics on the millisecond time scale have remained a challenge. We propose polarized shearing interference microscopy (PSIM), a single-shot quantitative polarization imaging method, for extracting the retardance and orientation angle of the laser beam transmitting through optically anisotropic specimens with complex structures. The measurement accuracy and imaging performance of PSIM are validated by imaging a birefringent resolution target and a bovine tendon specimen. We demonstrate that PSIM can quantify the dynamics of a flowing lyotropic chromonic liquid crystal in a microfluidic channel at an imaging speed of 506 frames per second (only limited by the camera frame rate), with a field-of-view of up to 350 × 350 μm2 and a diffraction-limit spatial resolution of ~2 μm. We envision that PSIM will find a broad range of applications in quantitative material characterization under dynamical conditions.

  View details for DOI 10.1021/acsphotonics.1c00788

  View details for PubMedID 37292495

  View details for PubMedCentralID PMC10249439

• Structures and topological defects in pressure-driven lyotropic chromonic liquid crystals. Proceedings of the National Academy of Sciences of the United States of America Zhang, Q., Zhang, R., Ge, B., Yaqoob, Z., So, P. T., Bischofberger, I. 2021; 118 (35)

  Abstract

  Lyotropic chromonic liquid crystals are water-based materials composed of self-assembled cylindrical aggregates. Their behavior under flow is poorly understood, and quantitatively resolving the optical retardance of the flowing liquid crystal has so far been limited by the imaging speed of current polarization-resolved imaging techniques. Here, we employ a single-shot quantitative polarization imaging method, termed polarized shearing interference microscopy, to quantify the spatial distribution and the dynamics of the structures emerging in nematic disodium cromoglycate solutions in a microfluidic channel. We show that pure-twist disclination loops nucleate in the bulk flow over a range of shear rates. These loops are elongated in the flow direction and exhibit a constant aspect ratio that is governed by the nonnegligible splay-bend anisotropy at the loop boundary. The size of the loops is set by the balance between nucleation forces and annihilation forces acting on the disclination. The fluctuations of the pure-twist disclination loops reflect the tumbling character of nematic disodium cromoglycate. Our study, including experiment, simulation, and scaling analysis, provides a comprehensive understanding of the structure and dynamics of pressure-driven lyotropic chromonic liquid crystals and might open new routes for using these materials to control assembly and flow of biological systems or particles in microfluidic devices.

  View details for DOI 10.1073/pnas.2108361118

  View details for PubMedID 34446562

  View details for PubMedCentralID PMC8536355

• Growth morphology and symmetry selection of interfacial instabilities in anisotropic environments. Soft matter Zhang, Q., Amooie, A., Bazant, M. Z., Bischofberger, I. 2021; 17 (5): 1202-1209

  Abstract

  The displacement of a fluid by another less viscous one in a quasi-two dimensional geometry typically leads to complex fingering patterns. In an isotropic system, dense-branching growth arises, which is characterized by repeated tip-splitting of evolving fingers. When anisotropy is present in the interfacial dynamics, the growth morphology changes to dendritic growth characterized by regular structures. We introduce anisotropy by engraving a six-fold symmetric lattice of channels on a Hele-Shaw cell. We show that the morphology transition in miscible fluids depends not only on the previously reported degree of anisotropy set by the lattice topography, but also on the viscosity ratio between the two fluids, ηin/ηout. Remarkably, ηin/ηout and the degree of anisotropy also govern the global features of the dendritic patterns, inducing a systematic change from six-fold towards twelve-fold symmetric dendrites. Varying either control parameter provides a new method to tune the symmetry of complex patterns, which may also have relevance for analogous phenomena of gradient-driven interfacial dynamics, such as directional solidification or electrodeposition.

  View details for DOI 10.1039/d0sm01706j

  View details for PubMedID 33427833

• Cyclic compressive creep-elastoplastic behaviors of in situ TiB₂/Al-reinforced composite MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING Zhang, Q., Zhang, W., Liu, Y., Guo, B. 2016; 666: 1-9

  View details for DOI 10.1016/j.msea.2016.04.010

  View details for Web of Science ID 000377312600001

• Evaluation and mathematical modeling of asymmetric tensile and compressive creep in aluminum alloy ZL109 MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING Zhang, Q., Zhang, W., Liu, Y. 2015; 628: 340-349

  View details for DOI 10.1016/j.msea.2015.01.032

  View details for Web of Science ID 000351965800043

• Exergy-based assessment and optimisation for energy transportation: a case study of Inner Mongolia-Tianjin INTERNATIONAL JOURNAL OF EXERGY Zhang, Q., Liu, Y., Zhang, W., Wu, X., Xia, X. 2015; 18 (3): 298-322

  View details for DOI 10.1504/IJEX.2015.072892

  View details for Web of Science ID 000364809300003