Hao Qi

Hybrid electrolytes with controlled network structures for lithium metal batteries.

Solid polymer electrolytes (SPEs) with tunable network structures are prepared by a facile one-pot reaction of polyhedral oligomeric silsesquioxane and poly(ethylene glycol). These SPEs, with high conductivity and high modulus, exhibit superior resistance to lithium dendrite growth even at high current densities. Measurements of lithium metal batteries with a LiFePO4 cathode show excellent cycling stability and rate capability.

Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery.

Correlated Perovskites as a New Platform for Super-Broadband-Tunable Photonics

We report strong and non-volatile optical modulation utilizing electron-doping induced phase change of a perovskite, SmNiO<inf>3</inf>. Broadband modulation (λ=400nm–17μm) is demonstrated using thin-film SmNiO<inf>3</inf>, and narrowband modulation is realized with metasurfaces integrated with SmNiO<inf>3</inf>.

Precisely Assembled Cyclic Gold Nanoparticle Frames by 2D Polymer Single‐Crystal Templating

In recent decades, extensive studies have been devoted to assembling nanoparticles (NPs) into various ordered structures to achieve novel optical properties. However, it still remains a challenging task to assemble NPs into cyclic one-dimensional (1D) shapes, such as rings and frames. Herein, we report a directed assembly method to precisely assemble NPs into well-defined, free-standing frames using polymer single crystals (PSCs) as the template. Preformed poly(ethylene oxide) (PEO) single crystals were used as the template to direct the crystallization of block copolymer (BCP) poly(ethylene oxide)-b-poly(4-vinylpyridine) (PEO-b-P4VP), which directs the gold NPs (AuNPs) to form AuNP frames. By controlling the PSC growth, we were able to, for the first time, precisely tune both the size and width of the AuNP frame. These novel AuNP frames topologically resemble NP nanorings and cyclic polymer chains, and show unique surface plasmon resonance (SPR) behaviors.

Impacts of maturation on the micromechanics of the meniscus extracellular matrix

To elucidate how maturation impacts the structure and mechanics of meniscus extracellular matrix (ECM) at the length scale of collagen fibrils and fibers, we tested the micromechanical properties of fetal and adult bovine menisci via atomic force microscopy (AFM)-nanoindentation. For circumferential fibers, we detected significant increase in the effective indentation modulus, Eind, with age. Such impact is in agreement with the increase in collagen fibril diameter and alignment during maturation, and is more pronounced in the outer zone, where collagen fibrils are more aligned and packed. Meanwhile, maturation also markedly increases the Eind of radial tie fibers, but not those of intact surface or superficial layer. These results provide new insights into the effect of maturation on the assembly of meniscus ECM, and enable the design of new meniscus repair strategies by modulating local ECM structure and mechanical behaviors.

Active metasurface devices based on correlated perovskites

There has been persistent exploration of new active materials and novel device architectures to dynamically control light with larger modulation depth and increased spectral range, at faster speed, and using less power. In this presentation, I will present experimental results showing that samarium nickelate (SmNiO3), a prototypical phase-change perovskite nickelate, exhibits reversible large refractive index changes over an ultra-broad spectral range, from the visible to the long-wavelength mid-infrared (λ = 400 nm-17 μm). The super broadband performance is due to strong electron correlation effects that allow extraordinarily large bandgap tuning of the order of 3 eV, and this new mechanism can be exploited to create active photonic devices.

Correlated perovskites as a new platform for super broadband tunable photonics

We report strong and non-volatile optical modulation utilizing electron-doping induced phase change of a perovskite, SmNiO 3 . Broadband modulation (λ=400nm–17μm) is demonstrated using thin-film SmNiO 3 , and narrowband modulation is realized with metasurfaces integrated with SmNiO 3 .