Mapping behavioral specifications to model parameters in synthetic biology

With recent improvements of protocols for the assembly of transcriptional parts, synthetic biological devices can now more reliably be assembled according to a given design. The standardization of parts open up the way for in silico design tools that improve the construct and optimize devices with respect to given formal design specifications. The simplest such optimization is the selection of kinetic parameters and protein abundances such that the specified design constraints are robustly satisfied. In this work we address the problem of determining parameter values that fulfill specifications expressed in terms of a functional on the trajectories of a dynamical model. We solve this inverse problem by linearizing the forward operator that maps parameter sets to specifications, and then inverting it locally. This approach has two advantages over brute-force random sampling. First, the linearization approach allows us to map back intervals instead of points and second, every obtained value in the parameter region is satisfying the specifications by construction. The method is general and can hence be incorporated in a pipeline for the rational forward design of arbitrary devices in synthetic biology

Rigid/Flexible Transparent Electronics Based on Separated Carbon Nanotube Thin-Film Transistors and Their Application in Display Electronics

Transparent electronics has attracted numerous research efforts in recent years because of its promising commercial impact in a wide variety of areas such as transparent displays. High optical transparency as well as good electrical performance is required for transparent electronics. Preseparated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose due to their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report fully transparent transistors based on separated carbon nanotube networks. Using a very thin metal layer together with indium tin oxide as source and drain contacts, excellent electrical performance as well as high transparency (∼82%) has been achieved (350–800 nm). Also, devices on flexible substrates are fabricated, and only a very small variation in electric characteristics is observed during a flexibility test. Furthermore, an organic light-emitting diode control circuit with significant output light intensity modulation has been demonstrated with transparent, separated nanotube thin-film transistors. Our results suggest the promising future of separated carbon nanotube based transparent electronics, which can serve as the critical foundation for next-generation transparent display applications

One-Step Thermo-Chemical Synthetic Method for Nanoscale One-Dimensional Heterostructures

One-Step Thermo-Chemical Synthetic Method for Nanoscale One-Dimensional Heterostructure

Macroelectronic Integrated Circuits Using High-Performance Separated Carbon Nanotube Thin-Film Transistors

Macroelectronic integrated circuits are widely used in applications such as flat panel display and transparent electronics, as well as flexible and stretchable electronics. However, the challenge is to find the channel material that can simultaneously offer low temperature processing, high mobility, transparency, and flexibility. Here in this paper, we report the application of high-performance separated nanotube thin-film transistors for macroelectronic integrated circuits. We have systematically investigated the performance of thin-film transistors using separated nanotubes with 95% and 98% semiconducting nanotubes, and high mobility transistors have been achieved. In addition, we observed that while 95% semiconducting nanotubes are ideal for applications requiring high mobility (up to 67 cm2 V−1 s−1) such as analog and radio frequency applications, 98% semiconducting nanotubes are ideal for applications requiring high on/off ratios (>104 with channel length down to 4 μm). Furthermore, integrated logic gates such as inverter, NAND, and NOR have been designed and demonstrated using 98% semiconducting nanotube devices with individual gating, and symmetric input/output behavior is achieved, which is crucial for the cascading of multiple stages of logic blocks and larger scale integration. Our approach can serve as the critical foundation for future nanotube-based thin-film macroelectronics

Template-Free Directional Growth of Single-Walled Carbon Nanotubes on a- and r-Plane Sapphire

We report high-throughput growth of highly aligned single-walled carbon nanotube arrays on a-plane and r-plane sapphire substrates. This is achieved using chemical vapor deposition with ferritin as the catalyst. The nanotubes are aligned normal to the [0001] direction for growth on the a-plane sapphire. They are typically tens of micrometers long, with a narrow diameter distribution of 1.34 ± 0.30 nm. In contrast, no orientation was achieved for growth on the c-plane and m-plane sapphire, or when Fe films, instead of ferritin, were used as the catalyst. Such orientation control is likely related to the interaction between carbon nanotubes and the sapphire substrate, which is supported by the observation that when a second layer of nanotubes was grown, they followed the gas flow direction. These aligned nanotube arrays may enable the construction of integrable and scalable nanotube devices and systems

Imperceptible and Ultraflexible p‑Type Transistors and Macroelectronics Based on Carbon Nanotubes

Flexible thin-film transistors based on semiconducting single-wall carbon nanotubes are promising for flexible digital circuits, artificial skins, radio frequency devices, active-matrix-based displays, and sensors due to the outstanding electrical properties and intrinsic mechanical strength of carbon nanotubes. Nevertheless, previous research effort only led to nanotube thin-film transistors with the smallest bending radius down to 1 mm. In this paper, we have realized the full potential of carbon nanotubes by making ultraflexible and imperceptible p-type transistors and circuits with a bending radius down to 40 μm. In addition, the resulted transistors show mobility up to 12.04 cm² V^–1_S^–1, high on–off ratio (∼10⁶), ultralight weight (<3 g/m²), and good mechanical robustness (accommodating severe crumpling and 67% compressive strain). Furthermore, the nanotube circuits can operate properly with 33% compressive strain. On the basis of the aforementioned features, our ultraflexible p-type nanotube transistors and circuits have great potential to work as indispensable components for ultraflexible complementary electronics

Growth of Aligned Single-Crystalline Rutile TiO₂ Nanowires on Arbitrary Substrates and Their Application in Dye-Sensitized Solar Cells

TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, we report synthesis of single-crystalline rutile phase TiO2 nanowires on arbitrary substrates, including fluorine-doped tin oxide (FTO), glass slides, tin-doped indium oxide (ITO), Si/SiO2, Si(100), Si(111), and glass rods. By controlling the growth parameters such as growth temperature, precursor concentrations, and so forth, we demonstrate that anisotropic growth of TiO2 is possible leading to various morphologies of nanowires. Optimization of the growth recipe leads to well-aligned vertical array of TiO2 nanowires on both FTO and glass substrates. Effects of various titanium precursors on the growth kinetics, especially on the growth rate of nanowires, are also studied. Finally, application of vertical array of TiO2 nanowires on FTO as the photoanode is demonstrated in dye-sensitized solar cell with an efficiency of 2.9 ± 0.2%

Growth of Aligned Single-Crystalline Rutile TiO₂ Nanowires on Arbitrary Substrates and Their Application in Dye-Sensitized Solar Cells

TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, we report synthesis of single-crystalline rutile phase TiO2 nanowires on arbitrary substrates, including fluorine-doped tin oxide (FTO), glass slides, tin-doped indium oxide (ITO), Si/SiO2, Si(100), Si(111), and glass rods. By controlling the growth parameters such as growth temperature, precursor concentrations, and so forth, we demonstrate that anisotropic growth of TiO2 is possible leading to various morphologies of nanowires. Optimization of the growth recipe leads to well-aligned vertical array of TiO2 nanowires on both FTO and glass substrates. Effects of various titanium precursors on the growth kinetics, especially on the growth rate of nanowires, are also studied. Finally, application of vertical array of TiO2 nanowires on FTO as the photoanode is demonstrated in dye-sensitized solar cell with an efficiency of 2.9 ± 0.2%

Free-Standing LiNi_0.5Mn_1.5O₄/Carbon Nanofiber Network Film as Lightweight and High-Power Cathode for Lithium Ion Batteries

Lightweight and high-power LiNi0.5Mn1.5O4/carbon nanofiber (CNF) network electrodes are developed as a high-voltage cathode for lithium ion batteries. The LiNi0.5Mn1.5O4/CNF network electrodes are free-standing and can be used as a cathode without using any binder, carbon black, or metal current collector, and hence the total weight of the electrode is highly reduced while keeping the same areal loading of active materials. Compared with conventional electrodes, the LiNi0.5Mn1.5O4/CNF network electrodes can yield up to 55% reduction in total weight and 2.2 times enhancement in the weight percentage of active material in the whole electrode. Moreover, the LiNi0.5Mn1.5O4/carbon nanofiber (CNF) network electrodes showed excellent current rate capability in the large-current test up to 20C (1C = 140 mAh/g), when the conventional electrodes showed almost no capacity at the same condition. Further analysis of polarization resistance confirmed the favorable conductivity from the CNF network compared with the conventional electrode structure. By reducing the weight, increasing the working voltage, and improving the large-current rate capability simultaneously, the LiNi0.5Mn1.5O4/CNF electrode structure can highly enhance the energy/power density of lithium ion batteries and thus holds great potential to be used with ultrathin, ultralight electronic devices as well as electric vehicles and hybrid electric vehicles

Nanosignal Processing: Stochastic Resonance in Carbon Nanotubes That Detect Subthreshold Signals

Experiments confirm that small amounts of noise help a nanotube transistor detect noisy subthreshold electrical signals. Gaussian, uniform, and impulsive (Cauchy) noise produced this feedforward stochastic-resonance effect by increasing both the nanotube system's mutual information and its input−output correlation. The noise corrupted a synchronous Bernoulli or random digital sequence that fed into the thresholdlike nanotube transistor and produced a Bernoulli sequence. Both Shannon's mutual information and correlation measured the performance gain by comparing the input and output sequences. This nanotube SR effect was robust:  it persisted even when infinite-variance Cauchy noise corrupted the signal stream. Such noise-enhanced signal processing at the nanolevel promises applications to signal detection in wideband communication systems and biological and artificial neural networks