Following the trend of miniaturization as per Moore's law, and facing the strong demand of next-generation electronic devices that should be highly portable, wearable, transplantable, and lightweight, growing endeavors have been made to develop novel flexible data storage devices possessing nonvolatile ability, high-density storage, high-switching speed, and reliable endurance properties. Nonvolatile organic data storage devices including memory devices on the basis of floating-gate, charge-trapping, and ferroelectric architectures, as well as organic resistive memory are believed to be favorable candidates for future data storage applications. In this Review, typical information on device structure, memory characteristics, device operation mechanisms, mechanical properties, challenges, and recent progress of the above categories of flexible data storage devices based on organic nanoscaled materials is summarized.

Recent Advances of Flexible Data Storage Devices Based on Organic Nanoscaled Materials.

Tissue engineering is a promising strategy to treat tissue and organ loss or damage caused by injury or disease. During the past two decades, mesenchymal stem cells (MSCs) have attracted a tremendous amount of interest in tissue engineering due to their multipotency and self-renewal ability. MSCs are also the most multipotent stem cells in the human adult body. However, the application of MSCs in tissue engineering is relatively limited because it is difficult to guide their differentiation toward a specific cell lineage by using traditional biochemical factors. Besides biochemical factors, the differentiation of MSCs also influenced by biophysical cues. To this end, much effort has been devoted to directing the cell lineage decisions of MSCs through adjusting the biophysical properties of biomaterials. The surface topography of the biomaterial-based scaffold can modulate the proliferation and differentiation of MSCs. Presently, the development of micro- and nano-fabrication techniques has made it possible to control the surface topography of the scaffold precisely. In this review, we highlight and discuss how the main topographical features (i.e., roughness, patterns, and porosity) are an efficient approach to control the fate of MSCs and the application of topography in tissue engineering.

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Topography: A Biophysical Approach to Direct the Fate of Mesenchymal Stem Cells in Tissue Engineering Applications.

Non-destructive profiling of volatile organic compounds using HS-SPME/GC-MS and its application for the geographical discrimination of white rice.

The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices Each individual component can be varied and acts cooperatively to tune gels' structure and function The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel The gel response is rapid, reversible, and reproducible These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.201700803

Tunable Gas Sensing Gels by Cooperative Assembly

Ferroelectric non-volatile memory devices are the most promising type of memory for future use in commercial applications. However, conventional planar organic ferroelectric memory transistors usually show poor performance in current density, operating speed and mechanical stability. There are three main factors which restrict the performance of organic ferroelectric memory transistors: the intrinsic low charge mobility of the organic semiconductor material; the large surface roughness of the ferroelectric layer; and the relative long channel length. In this research, a novel device architecture with an ultra-short channel length was invented. Benefiting from the short channel length, the memory device devised in this research exhibits a large current density of up to 6.32 mA cm−2 and a fast operating speed. Furthermore, the current flows across the semiconductor layer from the bottom mesh source electrode to the top drain electrode, which reduced the influence of the poor interface quality caused by the use of poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF–TrFe)] and enhances the performance of mechanical stability under bending. In addition, the main memory properties are comparable or superior to previously reported organic ferroelectric memories and inorganic ferroelectric memory with a vertical structure. Therefore, benefiting from the ultra-short channel length and special device structure, the ferroelectric memory in this research exhibited a large driving force, excellent bending characteristics and outstanding storage performance, which has great potential for wearable and flexible electric devices.

Flexible ultra-short channel organic ferroelectric non-volatile memory transistors

We fabricated ultra-flexible organic non-volatile ferroelectric 
field-effect transistors (FeFETs) with poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] on polyimide substrates, which adopted a solution-based top-contact/bottom-gate structure for low cost process without patterning. P(VDF-TrFE) gate dielectric layers and regioregular poly(3-hexylthiophene) active layers were formed by the spin-coating method. The field-effect mobility (μ
FE) was ∼0.28 cm2/V s, the on/off ratio was approximately 5.6 × 103, and the memory window (threshold voltage shift) was approximately 7 V. In addition, FeFETs were operated even at small bend radii without considerable changes in these values.

Solution-processed organic ferroelectric field-effect transistors on ultra-flexible substrates

A non-invasive method to characterize human mesenchymal stromal cells during adipogenic differentiation was developed for the first time. Seven fatty acid methyl esters (FAMEs), including methyl laurate, methyl myristate, methyl palmitate, methyl linoleate, methyl oleate, methyl elaidate and methyl stearate, were used for characterizing adipogenic differentiation using headspace solid-phase microextraction (HS-SPME) which is a very simple and non-invasive method for the extraction of volatile compounds. Glassware was used for culturing mesenchymal stromal cells rather than the common plasticware to minimize contamination by volatile impurities. The optimal SPME fiber was selected by comparing diverse fibers containing two pure liquid polymers (PDMS and PA) and two porous solids (PDMS/DVB and CAR/PDMS). Using optimized procedures, we discovered that seven FAMEs were only detected in adipogenic differentiated mesenchymal stromal cells and not in the mesenchymal stromal cells before differentiation. These data could support the quality control of clinical mesenchymal stromal cell culture in the pharmaceutical industry in addition to the development of many clinical applications using mesenchymal stromal cells.

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Non-invasive characterization of the adipogenic differentiation of human bone marrow-derived mesenchymal stromal cells by HS-SPME/GC-MS

Precursor films based on poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and P(VDF-TrFE) blended with Pb(Zr,Ti)O3 (PZT) were spin-coated on Si substrates and subsequently annealed at 150, 170, or 190°C. X-ray diffraction studies showed that the crystallization from the amorphous precursor films to the £ phase starts at higher annealing temperatures without involving the formation of other polymorphs when the P(VDF-TrFE) is blended with PZT, and the PZT content increases, resulting in an amorphous phase and/or crystalline £ phase. Nevertheless, a larger memory window width and much higher accumulation capacitance are induced by the blended PZT within the low operating voltage ranges from ¹0.5 to 2.0V and from ¹2.0 to 6.0V for 76.7 and 96.7wt% PZT blending, respectively. Furthermore, these improvements in the hysteretic characteristics in the capacitance­voltage measurements are also directly correlated with the degree of P(VDF-TrFE) crystallization and the presence of PZT. This approach enables viable routes toward the commercialization of nonvolatile ferroelectric memory devices and their market extension to potential applications as functional devices.

Crystallization and ferroelectric properties of the amorphous precursor films of Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) blended with Pb(Zr,Ti)O3

Kyung Eun Park

Papers

Solution-processed organic ferroelectric field-effect transistors on ultra-flexible substrates

Non-invasive characterization of the adipogenic differentiation of human bone marrow-derived mesenchymal stromal cells by HS-SPME/GC-MS

Crystallization and ferroelectric properties of the amorphous precursor films of Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) blended with Pb(Zr,Ti)O3

Ferroelectric properties of the organic films of poly(vinylidene fluoride-trifluoroethylene blended with inorganic Pb(Zr, Ti)O3

Characterizations of Blended PVDF/P(VDF-TrFE) Films for Ferroelectric Organic Field-Effect Transistors