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Jiuyun Shi

Publications and source records attributed to Jiuyun Shi.

3 recordsLinked to original sources

A monolithic fabrication platform for intrinsically stretchable polymer transistors and complementary circuits

Soft, stretchable organic field-effect transistors (OFETs) can provide powerful on-skin signal conditioning, but current fabrication methods are often material-specific: each new polymer semiconductor (PSC) requires a tailored process. The challenge is even greater for complementary OFET circuits, where two PSCs must be patterned sequentially, which often leads to device degradation. Here, we introduce a universal, monolithic photolithography process that enables high-yield, high-resolution stretchable complementary OFETs and circuits. This approach is enabled by a process-design framework that includes (i) a direct, photopatternable, solvent-resistant, crosslinked dielectric/semiconductor interface, (ii) broadly applicable crosslinked PSC blends that preserve high mobility, and (iii) a patterning strategy that provides simultaneous etch masking and encapsulation. Using this platform, we achieve record integration density for stretchable OTFTs (55,000 cm^-2), channel lengths down to 2 um, and low-voltage operation at 5 V. We demonstrate photopatterning across multiple PSC types and realize complementary circuits, including 3 kHz stretchable ring oscillators, the first to exceed 1 kHz and representing more than a 60-fold increase in stage switching speed over the state of the art. Finally, we demonstrate the first stretchable complementary OTFT neuron circuit, where the output frequency is modulated by the input current to mimic neuronal signal processing. This scalable approach can be readily extended to diverse high-performance stretchable materials, accelerating the development and manufacturing of skin-like electronics.

eess.SY

Self-dispersion of Two Natural Polysaccharides for Granular Composites

We envision that dispersion between two polymeric materials on mesoscales would create new composites with properties that are much more superior to the components alone. Here we elucidate the dispersion between two of most abundant natural polysaccharides, starch and chitosan, which form mesoscale composites that may promise many applications. By using X-ray microscopic imaging, small-angle X-ray scattering, and differential scanning calorimetry, we were able to characterize the interactions of chitosan and starch in the mesoscale composites. The morphology of the composite is far more complex from the simple mixture of starch granules with a nominal size of a few micrometers and chitosan microbundles of tens and hundreds of micrometers. This unique morphology can only be explained by the enhanced miscibility of chitosan in a starch granular matrix. It is evidenced that there is a possible ionic interaction between the amino group in chitosan and the hydroxyl groups in starch granules. Despite the limited solubility of chitosan in water, this ionic interaction allows for the disassembly of chitosan microbundles within the starch suspension. The result is a chemically stronger and more stable granular composite formed by two biocompatible and biodegradable polysaccharide polymers. The mechanism of chitosan to disperse throughout starch granules has implications for the application of chitosan in water and other solvents.

physics.chem-ph

Dynamic and programmable cellular-scale granules enable tissue-like materials

Tissue-like materials are required in many robotic systems to improve human-machine interactions. However, the mechanical properties of living tissues are difficult to replicate. Synthetic materials are not usually capable of simultaneously displaying the behaviors of the cellular ensemble and the extracellular matrix. A particular challenge is identification of a cell-like synthetic component which is tightly integrated with its matrix and also responsive to external stimuli at the population level. Here, we demonstrate that cellular-scale hydrated starch granules, an underexplored component in materials science, can turn conventional hydrogels into tissue-like materials when composites are formed. Using several synchrotron-based X-ray techniques, we reveal the mechanically-induced motion and training dynamics of the starch granules in the hydrogel matrix. These dynamic behaviors enable multiple tissue-like properties such as strain-stiffening, anisotropy, mechanical heterogeneity, programmability, mechanochemistry, impact absorption, and self-healability. The starch-hydrogel composites can be processed as robotic skins that maintain these tissue-like characteristics.

cond-mat.soft