important role in flexible electronics. [1][2][3] Nonvolatile resistive random access memories (RRAM) have simple structure, excellent scalability, high switching speed, good retention, and low power consumption. Thus, they have been considered as promising candidates for charge-based memory and Flash. [4,5] In terms of flexible RRAM (FRRAM) applications, the investigations mainly focus on device processing, resistive switching (RS) behaviors, and mechanical flexibilities. [6][7][8] Many efforts have been devoted to achieve high performance FRRAMs with both small RS parameters variation and excellent flexibility. One of the representative obstacles is the nonuniformity of RS parameters, which leads to false programming and gives rise to readout hazards. [9,10] Some FRRAMs demonstrated fast programming speed, large storage window, excellent flexibility, and mechanical endurance. However, the coefficients of variation for the RS parameters were unexpectedly high. [10] On the basis of conducting filament (CF) theory in RRAM devices, the switching mechanism is highly depended on the CF formation/disruption during the writing/programming process, which in turn affects the device performance. As concerned as the valence change memory (VCM) RRAM, oxygen vacancies play an important role in a redox reaction, which determines the filament morphology. In order to enhance the performance and improve the distribution of switching parameters, bilayer RS structure such as /indium tin oxide (ITO), is proposed. Such RS layer can control the formation/rupture of CF consisting of oxygen vacancies. [11][12][13] HfO 2 and TiO 2 are typical high dielectric constant transition metal oxides in complementary metal oxide semiconductor (CMOS) integrated circuit applications. Due to the simple compositions and good compatibilities with CMOS processing, they have been widely investigated for memory device applications. [14] Especially, HfO 2 /TiO 2 bilayer structure has exhibited desired features, including self-rectification, multiple resistance states, self compliance, and stable bipolar RS property. [14,15] Bilayer structure based RRAM can operate at low voltage, which decreases the heat accumulation in the operating process and reduces the power consumption. [16] Thus, it is speculated that the stability of bilayer HfO 2 /TiO 2 FRRAM device will be improved by avoiding the undesirable heating during the read/write process. The low energy consumptions and high stabilities are highly desirable for wearable electronic applications.The authors declare no conflict of interest. Figure 6. a) The 1000th, 1500th, and 2000th I-V curves taken on FRRAM device. b) I-V curves at different stop voltages ranged between −1.3 and −1.6 V with step of 0.1 V.www.advancedsciencenews.com

Solubilities of sebacic acid in binary ethanol + water solvent mixtures were measured by the dynamic method using a laser monitoring observation technique at a temperature range from (288 to 352) K. The mole fraction of ethanol in the solvent mixtures ranges from 0 to 1. The melting temperature and enthalpy of fusion of sebacic acid were determined by differential scanning calorimetry. The experimental results show that the slope of the solubility-temperature curve increases significantly with an increase in the mole fraction of ethanol in the solvent. The Wilson equation is applied to describe measured systems. The model parameters of the Wilson equation were expressed as a function of temperature.

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Flexible pressure sensors can by further classified into four general types based on the mechanisms: resistive, [3][4][5][6] capacitive, [7][8][9][10][11][12] piezoelectric, and triboelectric [13][14][15][16][17][18] type. Particularly, capacitive sensors are quite attractive due to their low power consumption and fast response time. However the confined electrode distance restricted its sensitivity, making it subject to parasitic charges and environmental electromagnetic noises. [19] In 2011, Pan's group originally demonstrated a new sensing mechanism, known as iontronic sensing. [20] Owing to the supercapacitive nature of the electrical double layer (EDL), the values order of unit area capacitance (UAC) could rocket from pF cm -2 to nF cm -2 even μF cm -2 , therefore the novel iontronic sensors usually show a much higher sensitivity compared with traditional capacitive sensors. [21][22][23][24][25][26][27][28][29][30][31] Despite significant progress in improving sensitivity, linear and wide detection range is still highly desirable in many applications. [32] To improve linear sensing performance, different structural designs have been proposed. For instance, hierarchical and multilayer structure provide linear output for resistive sensors; [33][34][35] linear response of capacitive sensors was achieved by regulating the dielectric constant variation with deformation. [36] However, these methods cannot be applied directly to iontronic sensors due to their disparate sensing mechanisms. Analogous strategies suitable for iontronic sensors yet still need to be studied. Furthermore, in a defined dynamic range, high sensitivity in the beginning consumes a major deformation and thus the sensing range is limited. Conversely, a sensor with wide sensing range can hardly detect slight pressure. Therefore, it is still a challenge to balance the sensitivity and wide sensing-range. Coincidentally, nature has already provided the answer. Evolving through natural selection, insects have evolved a variety of adaptations to adapt to different habitats. To adapt the environmental stimuli with several orders of magnitude, different receptors are employed to perceive slight and big pressure respectively. For instance, the insect organs used for mechanical transduction can be morphologically divided into tactile hairs and campaniform sensilla. [37] Different structures are used to detect different magnitudes of forces to achieve corresponding functions. Figure 1a shows the microstructures of mechanoreceptors of a parasitoid fly. As

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1×1 μm 2 via hole structure ZnO-based resistive random access memory cells are fabricated and the resistive switching behavior is investigated. It can be found that with 5.7% hafniumdoped ZnO film, the memory cell shows remarkable 10 8 pulse endurance. An ON/OFF resistance ratio of at least two orders of magnitude is achieved and the resistive states can remain stable up to 10 4 s. In contrast, a Pt/ZnO/TiN control device presents an unstable resistive switching characteristic and endurance degradation. Compared with pure ZnO film, Hf-doped ZnO film has a relatively smoother surface and larger band gap. X-ray photoelectron spectroscopy analysis indicates that the Hf-doped element induces more non-lattice oxygen ions in the ZnO switching layer. We deduce that the conductive filament forms/ruptures in a fixed path along the Hf atoms. Based on I-V curve fitting and temperature-dependent current measurements, the Pt/Hf:ZnO/TiN device is demonstrated as a Schottky conduction mechanism, which shows reasonable agreement with the possible resistive switching mechanism in the hafnium-doped ZnO memristive device.

The solubilities of sebacic acid in mixed solvents n-propanol + water have been measured by a dynamic method using a laser monitoring observation technique over a temperature range (288 to 351) K. A synergistic effect on solubility was found to occur in sebacic acid + n-propanol + water mixed systems. To detect the synergistic effect, solubilities of sebacic acid in 14.35 %, 36.97 %, 79.81 %, and 90.00 % mole fraction ethanol aqueous solution were determined to supplement our previous report. A weak synergistic effect was found for sebacic acid + ethanol + water mixed systems. The solid-liquid equilibrium (SLE) data have been fitted using the λh equation, the Wilson equation, and the NRTL equation. The comparison between the experimental and the calculated solubilities for the three models is reasonable, and the root-meansquare deviations for each system range from (0.30 to 1.95) K.