Abstract
By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. The purpose was to build up a system that mimics the motion of neurotransmitters in the synaptic cleft by obtaining an electrical to chemical signal transport. Fourier transform infrared (FTIR) spectroscopy and Raman measurements have demonstrated that electrochemical overoxidation region which separates the pristine PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The ultimate goal was to achieve the highest equilibrium current density at the lowest applied voltage via enhancing the electrical conductivity of PEDOT:PSS and ionic conductivity of electrochemically overoxidized region. The highest equilibrium current density, which corresponds to 4.81 × 1017 number of ions of acetylcholine was about 41 μA cm−2 observed for the OEIP with the electrical conductivities of 54 S cm−1. This was a threshold electrical conductivity beyond which the OEIP performances were not changed much. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 μA cm−2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here may provide a clue for their effortless mass production in the near future.
Highlights
Recent advancements in the electrochemical applications of conjugated polymers have increased the demand for their utilization in several progressive fields such as biosensors [1,2], actuators [3,4], transistors, and flexible electronics [5]
It was assumed that the electrochemical overoxidation of PEDOT:polystyrene groups (PSS) as a result leads to cutting off the electrical conductivity of overall conjugated polymer would end up in significant changes in its chemical structure
The deposition of PEDOT:PSS on flexible poly(ethylene terephthalate) (PET) substrate in pre-determined shapes was done by a line-patterning method, followed by drop-casting [5,9]
Summary
Recent advancements in the electrochemical applications of conjugated polymers have increased the demand for their utilization in several progressive fields such as biosensors [1,2], actuators [3,4], transistors, and flexible electronics [5]. In some cases multiple steps of patterning processes hinder the larges-scale production of these devices This field of study is quite advanced, there are still some restrictions related to the performance of organic electronic devices for their low release rates, high voltage demands, and limitations in design parameters. In this study a straightforward, but cost-effective and time-saving, method called line patterning is used to selectively deposit PEDOT:PSS conjugated polymer on PET substrate at desired shapes required for better ion pump performances. For the organic electronic ion pump (OEIP) structure, these conductivity values have never been reported In these studies it was indicated that the utilized PEDOT:PSS solution was of high conductivity grade [6,7,8].
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