Enabling and Localizing Omnidirectional Nonlinear Deformation in Liquid Crystalline Elastomers.

Liquid crystalline elastomers (LCEs) are widely recognized for their exceptional promise as actuating materials. Here, the comparatively less celebrated but also compelling nonlinear response of these materials to mechanical load is examined. Prior examinations of planarly aligned LCEs exhibit unidirectional nonlinear deformation to mechanical loads. A methodology is presented to realize surface-templated homeotropic orientation in LCEs and omnidirectional nonlinearity in mechanical deformation. Inkjet printing of the homeotropic alignment surface localizes regions of homeotropic and planar orientation within a monolithic LCE element. The local control of the self-assembly and orientation of the LCE, when subject to rational design, yield functional materials continuous in composition with discontinuous mechanical deformation. The variation in mechanical deformation in the film can enable the realization of nontrivial performance. For example, a patterned LCE is prepared and shown to exhibit a near-zero Poisson's ratio. Further, it is demonstrated that the local control of deformation can enable the fabrication of rugged, flexible electronic devices. An additively manufactured device withstands complex mechanical deformations that would normally cause catastrophic failure.

Solution-Processed Organic and Halide Perovskite Transistors on Hydrophobic Surfaces.

Solution-processable electronic devices are highly desirable due to their low cost and compatibility with flexible substrates. However, they are often challenging to fabricate due to the hydrophobic nature of the surfaces of the constituent layers. Here, we use a protein solution to modify the surface properties and to improve the wettability of the fluoropolymer dielectric Cytop. The engineered hydrophilic surface is successfully incorporated in bottom-gate solution-deposited organic field-effect transistors (OFETs) and hybrid organic-inorganic trihalide perovskite field-effect transistors (HTP-FETs) fabricated on flexible substrates. Our analysis of the density of trapping states at the semiconductor-dielectric interface suggests that the increase in the trap density as a result of the chemical treatment is minimal. As a result, the devices exhibit good charge carrier mobilities, near-zero threshold voltages, and low electrical hysteresis.

Versatile organic transistors by solution processing.

A selection of the latest developments in organic electronic materials and organic field-effect transistor (OFET) devices is reviewed here with an emphasis on the synthetic and manufacturing versatility, ease of processing, and low cost offered by solution processability. At the heart of these benefits is the nature of the weak van der Waals intermolecular interactions inherent to organic compounds. This allows processability with a relatively small amount of energy investment. Material solubility, in particular, creates unique pathways for film fabrication and the design of new device architectures, while presenting new manufacturing challenges to explore. In this review we provide a chronological presentation of the important developments in the solution-deposited organic small-molecule semiconductor, dielectric, and electrode materials used in OFETs, making specific note of current benchmarks. Organic device architectures and fabrication methods that are characterized by reduced complexity and ease of implementation are discussed.

Synthesis and charge transport studies of stable, soluble hexacenes.

Acenes larger than pentacene are predicted to possess enticing electronic properties, but are insoluble and prone to rapid decomposition. Utilizing a combination of functionalization strategies, we present stable, solution-processable hexacenes and an evaluation of their hole and electron transport properties.