11 research outputs found
Tailoring the Surface Chemistry of PEDOT:PSS to Promote Supported Lipid Bilayer Formation
This communication reports on a versatile and substrate-agnostic method to tune the surface chemistry of conducting polymers with the aim of bridging the chemical mismatch between bioelectronic devices and biological systems. As a proof of concept, the surface of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is grafted with a short-chain oligoethylene glycol monolayer to favor the formation of cell-derived supported lipid bilayers (SLBs). This method is tuned to optimize the affinity between the supported lipid bilayer and the conducting polymer, leading to significant improvements in bilayer quality and therefore electronic readouts. To validate the impact of surface functionalization on the system's ability to transduce biological phenomena into quantifiable electronic signals, the activity of a virus commonly used as a surrogate for SARS-CoV-2 (mouse hepatitis virus) is monitored with and without surface treatment. The functionalized devices exhibit significant improvements in electronic output, stemming from the improved SLB quality, therefore strengthening the case for the use of such an approach in membrane-on-a-chip systems
Low-voltage polyelectrolyte-gated polymer field-effect transistors gravure printed at high speed on flexible plastic substrates
We report the fabrication of polymer field effect transistors operating under a bias of |1V| in which the insulator and semiconductor are gravure printed on plastic at the high speed of 0.7 m s-1. Remarkably, the process does not necessitate any surface modification and relies solely on the careful selection and optimization of formulations based on solvent blends. In addition to demonstrating high-throughput fabrication, we fulfill another requirement for organic electronics and achieve low-voltage operation in ambient air by using a polyelectrolyte insulator, poly(4-styrenesulfonic acid) (PSSH). PSSH is a proton conductor that forms electrical double layers at the interfaces with the gate electrode and the semiconductor channel upon application of a small gate voltage (†|1 V|). Printed PSSH exhibits a high capacitance of 10 ΌF cm-2, leading to a printed poly(3-hexylthiophene) (P3HT) hole mobility above 0.1 cm2 V-1 s-1 in a bottom-gate, top-contact configuration
High performance photolithographically-patterned polymer thin-film transistors gated with an ionic liquid/poly(ionic liquid) blend ion gel
We demonstrate the fabrication of polymer thin-film transistors gated with an ion gel electrolyte made of the blend of an ionic liquid and a polymerised ionic liquid. The ion gel exhibits a high stability and ionic conductivity, combined with facile processing by simple drop-casting from solution. In order to avoid parasitic effects such as high hysteresis, high off-currents, and slow switching, a fluorinated photoresist is employed in order to enable high-resolution orthogonal patterning of the polymer semiconductor over an area that precisely defines the transistor channel. The resulting devices exhibit excellent characteristics, with an on/off ratio of 106, low hysteresis, and a very large transconductance of 3 mS. We show that this high transconductance value is mostly the result of ions penetrating the polymer film and doping the entire volume of the semiconductor, yielding an effective capacitance per unit area of about 200 ÎŒF cmâ2, one order of magnitude higher than the double layer capacitance of the ion gel. This results in channel currents larger than 1âmA at an applied gate bias of only â1âV. We also investigate the dynamic performance of the devices and obtain a switching time of 20âms, which is mostly limited by the overlap capacitance between the ion gel and the source and drain contacts
Nanoscale ion-doped polymer transistors
Organic transistors with submicron dimensions have been shown to deviate from the expected behaviour due to a variety of so-called 'short-channel' effects, resulting in nonlinear output characteristics and a lack of current saturation, considerably limiting their use. Here, using an electrochemically-doped polymer in which ions are dynamically injected and removed from the bulk of the semiconductor, we show that devices with nanoscale channel lengths, down to 50 nm, exhibit output curves with well-defined linear and saturation regimes. Additionally, they show very large on-currents on par with their microscale counterparts, large on-to-off ratios of 108, and record-high width-normalised transconductances above 10 S m-1. We believe this work paves the way for the fabrication of high-gain, high-current polymer integrated circuits such as sensor arrays operating at voltages below |1 V| and prepared using simple solution processing methods
High performance photolithographically-patterned polymer thin-film transistors gated with an ionic liquid/poly(ionic liquid) blend ion gel
Ion Pair Uptake in Ion Gel Devices Based on Organic Mixed IonicâElectronic Conductors
In organic mixed ionicâelectronic conductors (OMIECs), it is critical to understand the motion of ions in the electrolyte and OMIEC. Generally, the focus is on the movement of net charge during gating, and the motion of neutral anionâcation pairs is seldom considered. Uptake of mobile ion pairs by the semiconductor before electrochemical gating (passive uptake) can be advantageous as this can improve device speed, and both ions can participate in charge compensation during gating. Here, such passive ion pair uptake in high-speed solid-state devices is demonstrated using an ion gel electrolyte. This is compared to a polymerized ionic liquid (PIL) electrolyte to understand how ion pair uptake affects device characteristics. Using X-ray photoelectron spectroscopy, the passive uptake of ion pairs from the ion gel into the OMIEC is detected, whereas no uptake is observed with a PIL electrolyte. This is corroborated by X-ray scattering, which reveals morphological changes to the OMIEC from the uptake of ion pairs. With in situ Raman, a reorganization of both anions and cations is then observed during gating. Finally, the speed and retention of OMIEC-based neuromorphic devices are tuned by controlling the freedom of charge motion in the electrolyte
Recommended from our members
Tailoring the Surface Chemistry of PEDOT:PSS to Promote Supported Lipid Bilayer Formation
This communication reports on a versatile and substrateâagnostic method to tune the surface chemistry of conducting polymers with the aim of bridging the chemical mismatch between bioelectronic devices and biological systems. As a proof of concept, the surface of poly(3,4âethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is grafted with a shortâchain oligoethylene glycol monolayer to favor the formation of cellâderived supported lipid bilayers (SLBs). This method is tuned to optimize the affinity between the supported lipid bilayer and the conducting polymer, leading to significant improvements in bilayer quality and therefore electronic readouts. To validate the impact of surface functionalization on the system's ability to transduce biological phenomena into quantifiable electronic signals, the activity of a virus commonly used as a surrogate for SARSâCoVâ2 (mouse hepatitis virus) is monitored with and without surface treatment. The functionalized devices exhibit significant improvements in electronic output, stemming from the improved SLB quality, therefore strengthening the case for the use of such an approach in membraneâonâaâchip systems
Energetic control of redox-active polymers toward safe organic Bioelectronic materials
Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive sideâproducts. This is particularly important for bioelectronic devices, which are designed to operate in biological systems. While redoxâactive materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical sideâreactions with molecular oxygen during device operation. Here, electrochemical side reactions with molecular oxygen are shown to occur during organic electrochemical transistor (OECT) operation using highâperformance, stateâofâtheâart OECT materials. Depending on the choice of the active material, such reactions yield hydrogen peroxide (H2O2), a reactive sideâproduct, which may be harmful to the local biological environment and may also accelerate device degradation. A design strategy is reported for the development of redoxâactive organic semiconductors based on donorâacceptor copolymers that prevents the formation of H2O2 during device operation. This study elucidates the previously overlooked sideâreactions between redoxâactive conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyteâgated devices in applicationârelevant environments
Side chain redistribution as a strategy to boost organic electrochemical transistor performance and stability
A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [ÎŒC*] and current retentions up to 98% over 700 electrochemical switching cycles are developed