MRC Laboratory of Molecular Biology
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Inkjet Printed Circuits with 2D Semiconductor Inks for High-Performance Electronics
No full textAir-stable semiconducting inks suitable for complementary logic are key to create low-power printed integrated circuits (ICs). High-performance printable electronic inks with 2D materials have the potential to enable the next generation of high performance low-cost printed digital electronics. Here, the authors demonstrate air-stable, low voltage (<5 V) operation of inkjet-printed n-type molybdenum disulfide (MoS2), and p-type indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors (FETs), estimating an average switching time of τMoS2 ≈ 4.1 μs for the MoS2 FETs. They achieve this by engineering high-quality MoS2 and air-stable IDT-BT inks suitable for inkjet-printing complementary pairs of n-type MoS2 and p-type IDT-BT FETs. They then integrate MoS2 and IDT-BT FETs to realize inkjet-printed complementary logic inverters with a voltage gain |Av| ≈ 4 when in resistive load configuration and |Av| ≈ 1.4 in complementary configuration. These results represent a key enabling step towards ubiquitous long-term stable, low-cost printed digital ICs
Preferences for nutrients and sensory food qualities identify biological sources of economic values in monkeys
No full textValue is a foundational concept in reinforcement learning and economic choice theory. In these frameworks, individuals choose by assigning values to objects and learn by updating values with experience. These theories have been instrumental for revealing influences of probability, risk, and delay on choices. However, they do not explain how values are shaped by intrinsic properties of the choice objects themselves. Here, we investigated how economic value derives from the biologically critical components of foods: Their nutrients and sensory qualities. When monkeys chose nutrient-defined liquids, they consistently preferred fat and sugar to low-nutrient alternatives. Rather than maximizing energy indiscriminately, they seemed to assign subjective values to specific nutrients, flexibly trading them against offered reward amounts. Nutrient-value functions accurately modeled these preferences, predicted choices across contexts, and accounted for individual differences. The monkeys' preferences shifted their daily nutrient balance away from dietary reference points, contrary to ecological foraging models but resembling human suboptimal eating in free-choice situations. To identify the sensory basis of nutrient values, we developed engineering tools that measured food textures on biological surfaces, mimicking oral conditions. Subjective valuations of two key texture parameters- viscosity and sliding friction-explained themonkeys' fat preferences, suggesting a texture-sensing mechanism for nutrient values. Extended reinforcement learning and choice models identified candidate neuronal mechanisms for nutrient-sensitive decision-making. These findings indicate that nutrients and food textures constitute critical reward components that shape economic values. Our nutrientchoice paradigm represents a promising tool for studying food- reward mechanisms in primates to better understand human-like eating behavior and obesity
Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides (ACS Nano (2021) 15:5 (8780−8789) DOI: 10.1021/acsnano.1c01220)
No full textIn the methods section, “Device Preparation and Measurement”, the caption of Figure 5 incorrectly stated, “An example of the gate voltage versus mobility for different chemical treatment steps.” This should instead state, “Example transfer curves showing the conductivity, σ, as a function of back gate, VG, for MoS2 devices after different treatments.” This is correctly described in the text referring to this figure, but the caption was mislabeled. The amended Figure 5 appears below. We apologize for the mistake in the original submission
IoT-to-the-Rescue: A Survey of IoT Solutions for COVID-19-like Pandemics
No full textThe atmospheric buoyancy and intangible nature of fatal communicable viruses lead to rapid transmissions among individuals, resulting in global pandemics. Strategic lockdowns and mandatory social distancing are immediate solutions in such scenarios. However, this leads to operational disruptions in education, manufacturing, economy, transportation, governance, and community. Although technological assistance is beneficial in overcoming such issues, the current Internet of Things (IoT) infrastructure has limitations. In this paper, we provide a comprehensive review of the possible IoT-based solutions that have the capacity of combating the COVID-19-like viruses. We highlight the societal impacts due to pandemics and identify the specific lacunae in current IoT solutions. We also provide comprehensive detail on how to overcome the challenges along with directions towards the possible technological trends for future research. Compared to existing reviews, our work offers a holistic view of the cause, effects, and the possible solutions that are existing, along with already existing solutions that can be customized to serve the special needs during the pandemic
Experimental Observation of Temperature and Pressure Induced Frequency Fluctuations in Silicon MEMS Resonators
No full textSilicon MEMS resonators are increasingly being adopted for applications in timing and frequency control, as well as precision sensing. It is well established that a key limitation to performance is associated with sensitivity to environmental variables such as temperature and pressure. As a result, technical approaches to address these factors such as vacuum sealing and ovenization of the resonators in a temperature controlled system have been introduced. However, residual sensitivity to such effects can still serve as a significant source of frequency fluctuations and drift in precision devices. This is experimentally demonstrated in this paper for a precision oven-controlled and vacuum-sealed silicon resonators. The frequency fluctuations of oscillators constructed using two separate nearly-identical co-located resonators on the same chip are analysed and differential frequency fluctuations are examined as a means of reducing the impact of common-mode effects such as temperature and pressure. For this configuration, our results show that the mismatch of temperature and pressure coefficients between the resonators ultimately limits the frequency stability. [2020-0395
Non-isothermal phase-field simulations of laser-written in-plane SiGe heterostructures for photonic applications
No full textAdvanced solid-state devices, including lasers and modulators, require semiconductor heterostructures for nanoscale engineering of the electronic bandgap and refractive index. However, existing epitaxial growth methods are limited to fabrication of vertical heterostructures grown layer by layer. Here, we report the use of finite-element-method-based phase-field modelling with thermocapillary convection to investigate laser inscription of in-plane heterostructures within silicon-germanium films. The modelling is supported by experimental work using epitaxially-grown Si0.5Ge0.5 layers. The phase-field simulations reveal that various in-plane heterostructures with single or periodic interfaces can be fabricated by controlling phase segregation through modulation of the scan speed, power, and beam position. Optical simulations are used to demonstrate the potential for two devices: graded-index waveguides with Ge-rich (>70%) cores, and waveguide Bragg gratings with nanoscale periods (100–500 nm). Periodic heterostructure formation via sub-millisecond modulation of the laser parameters opens a route for post-growth fabrication of in-plane quantum wells and superlattices in semiconductor alloy films
Local and distributed manufacturing during the COVID-19 pandemic: Is crisis a window of opportunity for sustainable development in the Global South?
No full textShortages of critical items during the COVID-19 pandemic have led to a widespread mobilization of open, local and distributed manufacturing. In this paper, we examine the potential systemic impacts of these activities in the Global South, using the Multi-Level Perspective from literature on sustainability transitions. We conduct a longitudinal case study of a non-governmental organization that has been pioneering distributed manufacturing solutions in the Global South for almost a decade. We illustrate that the pandemic is a major landscape event that is having profound impacts on the existing socio-technical regime and niche levels. We show how niches mature over time, and that the pandemic has created an opportunity for niche replication and alignment. We present an initial analysis of factors that support and resist the path dependency of the existing regime. Thus, we speculate about the possibility to transition away from a development model predicated on the transfer of products from the North to the South, to an endogenous model of sustainable development that is underpinned by local design and production in the South. Here we show that crisis creates a key window of opportunity for sustainable development in the Global South through the formation of distributed manufacturing networks
Linearisation Method of DML-based Transmitters for Optical Communications, Part I: Theory and Simulation Studies
No full textThe performance of directly-modulated lasers (DMLs) is severely impaired by nonlinear behaviour when operating at high symbol rates. We propose a new linearization method for DML-based transmitters which can significantly reduce nonlinearity. This method, named the Stretched A (StrA) method, relies on the generation of an approximation to the ideal modulating current that generates a linear optical output waveform. In Part I of this work, the theoretical framework of the proposed method is presented and detailed simulation studies illustrate its implementation and demonstrate the benefits it offers. Although the method is applicable to any type of DML, the simulation studies presented herein focus on optical links based on vertical-cavity surface-emitting lasers (VCSELs) as these comprise the vast majority of short-reach optical links. Part II of this work presents the proof-of-principle experimental demonstration of this new linearization method and discusses its possible implementations using either analog or digital electronics