Organic electrochemical transistors (OECTs) are attracting a great deal of interest for biosensing and bioelectronics applications. However, their device physics is not yet well-understood. In this paper, we focus on the effect of the gate electrode material on the response of OECTs. We studied OECTs made from the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate), and which utilized halide electrolytes. We demonstrate that OECTs with Ag gate electrodes show larger current modulation compared to OECTs with Pt gate electrodes. This effect is due to a change in the OECT regime of operation from capacitive, in case of a Pt gate electrode, to Faradaic, in the case of an Ag electrode.

This perspective deals with the coupling of ionic and electronic transport in organic electronic devices, focusing on electrolyte-gated transistors. These include electrolyte-gated organic field-effect transistors (EG-OFETs) and organic electrochemical transistors (OECTs). EG-OFETs, based on molecules and polymers, can be operated at low electrical bias (about 1 V or below) and permit unprecedented charge carrier densities within the transistor channel. OECTs can be operated in aqueous environment as efficient ion-to-electron converters, thus providing an interface between the worlds of biology and electronics. The exploration and the exploitation of coupled ionic and electronic transport in organic materials brings together different disciplines such as materials science, physics, chemistry, electrochemistry, organic electronics and biology.

The golden rule in tissue engineering is the creation of a synthetic device that simulates the native tissue, thus leading to the proper restoration of its anatomical and functional integrity, avoiding the limitations related to approaches based on autografts and allografts. The emergence of synthetic biocompatible materials has led to the production of innovative scaffolds that, if combined with cells and/or bioactive molecules, can improve tissue regeneration. In the last decade, silk fibroin (SF) has gained attention as a promising biomaterial in regenerative medicine due to its enhanced bio/cytocompatibility, chemical stability, and mechanical properties. Moreover, the possibility to produce advanced medical tools such as films, fibers, hydrogels, 3D porous scaffolds, non-woven scaffolds, particles or composite materials from a raw aqueous solution emphasizes the versatility of SF. Such devices are capable of meeting the most diverse tissue needs; hence, they represent an innovative clinical solution for the treatment of bone/cartilage, the cardiovascular system, neural, skin, and pancreatic tissue regeneration, as well as for many other biomedical applications. The present narrative review encompasses topics such as (i) the most interesting features of SF-based biomaterials, bare SF’s biological nature and structural features, and comprehending the related chemo-physical properties and techniques used to produce the desired formulations of SF; (ii) the different applications of SF-based biomaterials and their related composite structures, discussing their biocompatibility and effectiveness in the medical field. Particularly, applications in regenerative medicine are also analyzed herein to highlight the different therapeutic strategies applied to various body sectors.

A single natural cotton fiber has been functionalized with poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) conductive polymer by a simple soaking process and used as a channel of an organic electrochemical transistor (OECT), directly interfaced with a liquid electrolyte in contact with an Ag wire gate. The device shows a stable and reproducible current modulation and has been demonstrated to be very effective for electrochemical sensing of NaCl concentration in water. The single wire cotton fiber OECT results to be a simple and low cost device, which is very attractive for wearable electronics in fitness and healthcare.

We investigate and optimize the Aerosol Jet Printing of PEDOT:PSS by studying the role of parameters determining the final quality of the printed features. Printing thin films of organic materials requires a high control in the deposition process to control the morphology/structure of the films that determine the electrical and functional performance of organic devices. We studied aerosol jet printed lines of the PEDOT:PSS semiconductive polymer on flexible Kapton substrates. We choose the focus ratio, defined as the ratio between the sheath and carrier gas flow rates, as the main parameter that best characterizes the process and hence the characteristics of printed lines. A detailed analysis of the line width and thickness, as a function of the focus ratio and carrier gas flow for different nozzle sizes and sheath gas flow rates, is reported. The edge profile definition of printed PEDOT:PSS lines has been found to be affected by a combination of overspray, typical of aerosol deposition, and pinholes due to the Kapton/PEDOT:PSS interaction, while their core profile results to be almost defects free. An optimal printing window for different nozzle sizes has been determined in terms of a minimization of overspray/pinholes effects with respect to the whole line width. Finally, an array of whole-plastic, planar Organic Electrochemical Transistors, having both the channel and the gate electrode made of PEDOT:PSS, has been manufactured using the best combination of process parameters. Transistors have been characterized for different channel/gate area ratios and the transconductance analysed as a function of channel to gate area.