Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices.

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbon-based semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices

Bias-dependent effects in planar perovskite solar cells based on CH3NH3PbI3−xClx films

A unique bias-dependent phenomenon in CH3NH3PbI3-xClx based planar perovskite solar cells has been demonstrated, in which the photovoltaic parameters derived from the current-voltage (I-V) curves are highly dependent on the initial positive bias of the I-V measurement. In FTO/CH3NH3PbI3-xClx/Au devices, the open-circuit voltage and short-circuit current increased by ca. 337.5% and 281.9% respectively, by simply increasing the initial bias from 0.5 V to 2.5 V. (C) 2015 Elsevier Inc. All rights reserved

Dynamic 13C Flux Analysis Captures the Reorganization of Adipocyte Glucose Metabolism in Response to Insulin.

Cellular metabolism is dynamic, but quantifying non-steady metabolic fluxes by stable isotope tracers presents unique computational challenges. Here, we developed an efficient 13C-tracer dynamic metabolic flux analysis (13C-DMFA) framework for modeling central carbon fluxes that vary over time. We used B-splines to generalize the flux parameterization system and to improve the stability of the optimization algorithm. As proof of concept, we investigated how 3T3-L1 cultured adipocytes acutely metabolize glucose in response to insulin. Insulin rapidly stimulates glucose uptake, but intracellular pathways responded with differing speeds and magnitudes. Fluxes in lower glycolysis increased faster than those in upper glycolysis. Glycolysis fluxes rose disproportionally larger and faster than the tricarboxylic acid cycle, with lactate a primary glucose end product. The uncovered array of flux dynamics suggests that glucose catabolism is additionally regulated beyond uptake to help shunt glucose into appropriate pathways. This work demonstrates the value of using dynamic intracellular fluxes to understand metabolic function and pathway regulation

A Personal Respirator to Improve Protection for Healthcare Workers Treating COVID-19 (PeRSo)

Introduction: SARS-CoV-2 infection is a global pandemic. Personal Protective Equipment (PPE) to protect healthcare workers has been a recurrent challenge in terms of global stocks, supply logistics and suitability. In some settings, around 20% of healthcare workers treating COVID-19 cases have become infected, which leads to staff absence at peaks of the pandemic, and in some cases mortality.Methods: To address shortcomings in PPE, we developed a simple powered air purifying respirator, made from inexpensive and widely available components. The prototype was designed to minimize manufacturing complexity so that derivative versions could be developed in low resource settings with minor modification.Results: The “Personal Respirator – Southampton” (PeRSo) delivers High-Efficiency Particulate Air (HEPA) filtered air from a battery powered fan-filter assembly into a lightweight hood with a clear visor that can be comfortably worn for several hours. Validation testing demonstrates that the prototype removes microbes, avoids excessive CO2 build-up in normal use, and passes fit test protocols widely used to evaluate standard N95/FFP2 and N99/FFP3 face masks. Feedback from doctors and nurses indicate the PeRSo prototype was preferred to standard FFP2 and FFP3 masks, being more comfortable and reducing the time and risk of recurrently changing PPE. Patients report better communication and reassurance as the entire face is visible.Conclusion: Rapid upscale of production of cheaply produced powered air purifying respirators, designed to achieve regulatory approval in the country of production, could protect healthcare workers from infection and improve healthcare delivery during the COVID-19 pandemic

Lactate production is a prioritized feature of adipocyte metabolism

Adipose tissue is essential for whole-body glucose homeostasis, with a primary role in lipid storage. It has been previously observed that lactate production is also an important metabolic feature of adipocytes, but its relationship to adipose and whole-body glucose disposal remains unclear. Therefore, using a combination of metabolic labeling techniques, here we closely examined lactate production of cultured and primary mammalian adipocytes. Insulin treatment increased glucose uptake and conversion to lactate, with the latter responding more to insulin than did other metabolic fates of glucose. However, lactate production did not just serve as a mechanism to dispose of excess glucose, because we also observed that lactate production in adipocytes did not solely depend on glucose availability and even occurred independently of glucose metabolism. This suggests that lactate production is prioritized in adipocytes. Furthermore, knocking down lactate dehydrogenase specifically in the fat body of Drosophila flies lowered circulating lactate and improved whole-body glucose disposal. These results emphasize that lactate production is an additional metabolic role of adipose tissue beyond lipid storage and release

Mitochondrial oxidants, but not respiration, are sensitive to glucose in adipocytes

Insulin action in adipose tissue is crucial for whole-body glucose homeostasis, with insulin resistance being a major risk factor for metabolic diseases such as type 2 diabetes. Recent studies have proposed mitochondrial oxidants as a unifying driver of adipose insulin resistance, serving as a signal of nutrient excess. However, neither the substrates for nor sites of oxidant production are known. Since insulin stimulates glucose utilisation, we hypothesised that glucose oxidation would fuel respiration, in turn generating mitochondrial oxidants. This would impair insulin action, limiting further glucose uptake in a negative feedback loop of ‘glucose-dependent’ insulin resistance. Using primary rat adipocytes and cultured 3T3-L1 adipocytes, we observed that insulin increased respiration, but notably this occurred independently of glucose supply. In contrast, glucose was required for insulin to increase mitochondrial oxidants. Despite rising to similar levels as when treated with other agents that cause insulin resistance, glucose-dependent mitochondrial oxidants failed to cause insulin resistance. Subsequent studies revealed a temporal relationship whereby mitochondrial oxidants needed to increase before the insulin stimulus to induce insulin resistance. Together, these data reveal that a) adipocyte respiration is principally fuelled from non-glucose sources, b) there is a disconnect between respiration and oxidative stress, whereby mitochondrial oxidant levels do not rise with increased respiration unless glucose is present, and c) mitochondrial oxidative stress must precede the insulin stimulus to cause insulin resistance, explaining why short-term insulin-dependent glucose utilisation does not promote insulin resistance. These data provide additional clues to mechanistically link nutrient excess to adipose insulin resistance.DEJ was supported by a National Health and Medical Research Council (NHMRC) Senior Principal Research Fellowship (APP1019680) and NHMRC project grants (GNT1061122, GNT1086851). GJC was supported by a Professorial Research Fellowship from the University of Sydney Medical School. DEJ and GJC were also supported by an NHMRC project grant (GNT1086850). JRK was funded by an NHMRC Early Career Fellowship (APP1072440), Australian Diabetes Society Skip Martin Early-Career Fellowship, Diabetes Australia Research Program grant, and CPC Early-Career Seed Funding grant. DJF was funded by Medical Research Council Career Development Award (MR/S007091/1)

Fabrication and characterisation of organic thin-film transistors for sensing applications

Research Doctorate - Doctor of Philosophy (PhD)Organic thin-film transistors (OTFTs) are a family of devices in the area of organic electronics which are generating a large amount of interest due to the wide variety of potential applications for transistors which have all the benefits associated with using organic materials. These benefits include low-temperature and low-power fabrication possibilities, the use of flexible substrates and the low cost of materials. Previous literature on OTFTs comprising poly-3-hexylthiophene (P3HT) semiconductor layers, poly(4-vinylphenol) (PVP) dielectric layers and poly(3,4-ethylenedioxy-thiophene) poly(styrenesulfonate) (PEDOT:PSS) gate electrodes have reported on their relatively high performance at low operating voltages. However, there still remains the potential for further investigations to discover more about the nature of the current modulation mechanism(s) in these types of OTFTs. Several experiments were carried out to probe their operation mechanisms and determine their suitability for applications such as biosensors. The results of many of these experiments indicated that ions donated from the acidic PEDOT:PSS gate material as well as those liberated from water in air contribute to current modulation by doping and de-doping of the P3HT semiconductor. Poly(vinyl-pyridine) (PVPy) was then introduced as a dielectric material to replace PVP. PVPy contrasts in its chemical properties with PVP: rather than allowing and contributing to the free movement of protons within it as the acidic PVP does, the chemically basic PVPy will tend to bind protons to its pyridal groups, restricting their movement. It was shown that this change in material reduces the off current (I_OFF) of the devices (by inhibiting any doping of P3HT which occurs upon PEDOT:PSS deposition), however the on current (I_ON) was also reduced and thus no real improvement in current modulation ration(I_ON/I_OFF) was achieved. Whilst some aspects of device performance were improved when PVPy was used as the dielectric layer instead of PVP, the current modulation ratio remained low. Subsequent experiments showed that the addition of a dopant salt (LiClO₄) to the PVPy layer can substantially increase the current modulation ratio of the OTFTs. In fact, it was demonstrated that the current modulation ratio can be controlled by varying the amount of salt added to each device. The nature of the drain current (I_D) response to changes in gate voltage (V_GS) in the time domain indicates that electrochemical doping, and not an electrostatic mechanism, is the nature of the mechanism causing current modulation (similar to the previous un-doped devices). NaClO₄ was also trialled as a candidate for the dopant salt and, despite Na⁺ being larger than Li⁺, it appeared to move more freely within the device which is consistent with a hydration sphere model and therefore supports the idea that the dielectric layer is moisture-rich when operating in air. Finally, OTFTs incorporating the enzyme glucose oxidase (GOX) were fabricated for use as glucose sensors. GOX selectively oxidises glucose and it was hypothesised that the ions liberated in this oxidation reaction could contribute to the ionic processes which contribute to current modulation in the devices and therefore a relationship between the quantity of glucose exposed to the device and the I_D level could be established. The results presented here show that devices with embedded GOX do indeed show a relationship between glucose concentration and I_D when an analyte solution is deposited onto the device