How do electrochemical transistors work

Abstract:Introduction: Organic electrochemical transistors based on the polymer poly (3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) are biosensors, which p-type transistor show characteristics based on the movement of Cations in and out of the polymer layer. The sensor configuration consists of three Contacts: the source, the drain and the gate electrode, with the polymer layer is separated from the gate electrode by an electrolyte. The cations from the Electrolytes are fed into the PEDOT: PSS by the applied voltage, where they compensate for the open sulfonate anions of the PSS. This in turn increases the Density of the holes in the PEDOT, which leads to a drop in the drain current. This A drop in current results in the sensor being switched off. This sensor behavior can can be used for a wide variety of biological measurements. The OECTs can be used and allow for the detection of electrically active cells at the same time the measurement of cell adhesion. The use of these sensors for the Measurement of data from confluent cell layers up to single cell measurements in Combination with a mathematical description of the results has been used so far not shown yet. Results: In order to produce universally applicable, highly sensitive and transparent sensors, Established clean room processes were used in a new and simplified way. Factors that cause damage to the polymer layer during sensor production such as ultraviolet radiation have been completely eliminated. The Sensors have been used in Tested in both wet and dry conditions. The test procedure made the Establishing the optimal parameters for the production of organic electrochemical transistors. The most important factor for sensor behavior was determines the volume of the polymer layer. The volume of the PEDOT: PSS is determined the electrical properties of the sensors. What remains is the volume of the polymer layer constant for the sensors, the same transconductance is measured, one However, change in the layer thickness leads to a different behavior with regard to the Cutoff frequency. Thinner layers show an increase in the cutoff frequency, whereby thicker layers show the opposite effect. Because of this, had to be a optimized design to ensure the correct function of the sensors for the planned experiments. Different cell types were used to test a wide range of applications for the fabricated sensors. Heart cells were used to measure extracellular action potentials. The sensors tested showed a very good signal-to-noise ratio fast measurement times, making them ideal sensors for action potential measurements makes. At the same time transistor transfer function measurements were carried out, to explore the capabilities of the sensors in the area of ‚Äč‚Äčimpedance measurements. This type of measurement has not yet been published. By using of densely growing Madin-Darbey kidney cells could change the Cell impedance can be measured by changes in the cell connections. in the In contrast to the Madin-Darbey Kidney cells, Human Embryo Kidney grows Cells without cell connections. Since the measurement of dense cell cultures is only indicative allowed over the population of cells as a whole, new protocols have been developed to measure at the single cell level. The organic electrochemical transistors demonstrated the ability to act potentials of cells as well as their adhesion with high Measure reproducibility and precision. Organic electrochemical Transistors that perform the transistor transfer function down to the single cell level benefits have not yet been shown. In addition, a mathematical model was created designed to determine the cell parameters from the data obtained. The mathematical model serves to improve the understanding regarding the interaction of cells and the sensors. The combination of those shown Biosensors with optical transparency and the possibility of mathematical Fitting the data allows for innumerable experiments. Outlook: The sensors shown offer an excellent platform for biosensing with the Possibility for many future uses. The sensors are not on that applications shown are limited, but can be used with simple means for the can be adapted to a wide variety of purposes.
Summary: Organic electrochemical transistors based on the polymer poly (3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) are biosensors which use the movement of cations into and out of the polymer layer to generate a behavior that mimics p-type transistor. The device configuration has a source contact, a drain contact, and a gate electrode, which is separated from the polymer layer by an electrolyte. The cations of the electrolyte enter the PEDOT: PSS and compensate the pendant sulfonate anions on the PSS which increases the hole density in PEDOT. This results in a decrease in the drain current and a switching of the device into the off state. Using this device behavior, several biological signals can be detected. The OECTs can be used for the detection of action potentials of electrogenic cells, but also enable the measurement of the adhesion of cells to the device. The utilization of these devices for the measurement of confluent cell layers down to single cells in combination with a mathematical description was not shown so far. Results: In order to achieve versatile, highly sensitive, and transparent sensors, the fabrication of the devices with standard cleanroom processes was established in a unique and simplified way. Deteriorating factors such as exposure to ultraviolet radiation and contact with water were eliminated from the fabrication process. The sensors were characterized in regards to their electrical performance and stability in dry and wet conditions. The gathered results were used to generate a protocol for the best performing chips. Based on the generated data protocols for the fabrication, chemical post-treatment, as well as device operation, were established. Different sensing areas of the polymer layer were tested to determine their advantages for biosensing. The crucial factor for the devices was based on the volume of the deposited polymer layer. By keeping the volume of the PEDOT: PSS constant the transconductance remains the same, however thicker PEDOT: PSS layers resulted in devices with a comparatively lower cutoff frequency while thinner polymer layers resulted in a comparatively higher cutoff frequency. Therefore, an optimized chip layout had to be made to guarantee the functionality of the devices for their applications. Different cell types were used to test the devices towards their cell-sensing capabilities. Cardiomyocytes were used to establish the sensors for action potential measurements, and it was found that the sensors inherit a high signal-to-noise ratio making these devices ideal candidates for action potential measurements. At the same time, the impedimetric capabilities of the devices were investigated according to transistor-transfer function measurements which were not shown before with PEDOT: PSS based organic electrochemical transistor. By using densely growing cells, such as the Madin-Darby canine kidney cells, the change in impedance spectra towards changes in gap junction resistance could be proven. Human embryo kidney cells were used to investigate the behavior of dense cell cultures when no gap junctions are present. Since the observation of dense cellular cultures only allows for experiments on an arbitrary amount of cells, a protocol was established, and the devices were tested for measurements on a single cell level. The devices showed the capability for measurements of action potentials with the additional impedimetric data in high precision and reproducibility. Devices utilizing transistor-transfer function measurements with organic electrochemical transistors down to single cell level have not been shown so far. In addition, a new mathematical model was developed in order to calculate the cell-related parameters which demonstrate the distance between the cell and the polymer, offering a closer insight into the cellular attachment and detachment behavior. In combination with the fitting, the present platform was established with several possible applications ranging from confluent cells down to single cells while also offering the possibility of optically controlling the cell behavior due to the transparency of the devices. Outlook: The established devices offer an excellent biosensing platform which can be used in several future applications. The devices are not limited to the applications shown and can be altered to fit the desired use.