Biocompatible, biodegradable, and solid‐state electrolyte‐based organic transistors are demonstrated. As the electrolyte is composed of all edible materials, which are levan polysaccharide and choline‐based ionic liquid, the organic transistor fabricated on the electrolyte can be biocompatible and biodegrable. Compared to the other ion gel based electrolytes, it has superior electrical and mechanical properties, large specific capacitance (≈40 µF cm−2), non‐volatility, flexibility, and high transparency. Thus, it shows mechanical reliability by maintaining electrical performances under up to 1.11% of effective bending strain, 5% of stretching, and have low operation voltage range when it is utilized in organic transistors. Moreover, the biodegradable electrolyte‐based organic transistors can be applied to bio‐integrated devices, such as electrocardiogram (ECG) recordings on human skin and the heart of a rat. The measured ECG signals from the transistors, compared to signals from electrode‐based sensors, has a superior signal‐to‐noise ratio. The biocompatible and biodegradable materials and devices can contribute to the development of many bioelectronics.
Bioelectronics needs to continuously monitor mechanical and electrophysiological signals for patients. However, the signals always include artifacts by patients’ unexpected movement (such as walking and respiration under approximately 30 hertz). The current method to remove them is a signal process that uses a bandpass filter, which may cause signal loss. We present an unconventional bandpass filter material—viscoelastic gelatin-chitosan hydrogel damper, inspired by the viscoelastic cuticular pad in a spider—to remove dynamic mechanical noise artifacts selectively. The hydrogel exhibits frequency-dependent phase transition that results in a rubbery state that damps low-frequency noise and a glassy state that transmits the desired high-frequency signals. It serves as an adaptable passfilter that enables the acquisition of high-quality signals from patients while minimizing signal process for advanced bioelectronics.
Squaraine dyes (SQs) are an important class of polymethine dyes with a unique reasonable‐stabilized zwitterionic structure, in which electrons are highly delocalized over the conjugated bridge. These dyes can not only be easily synthesized via a condensation, but also exhibit intense absorption and emission in the visible and near‐infrared region with excellent photochemical stability, making them attractive material candidates for many photoelectric and biomedical applications. Thus, in this review, after an introduction of SQs, the recent advances of SQs in the photovoltaic field are comprehensively summarized including dye‐sensitized solar cells, organic solar cells, and perovskite solar cells. Then, the important advances in the use of SQs as the biosensors, biological imaging, and photodynamic/photothermal therapy reagents in the biomedical field are also discussed. Finally, a summary and outlook will be provided with some new perspectives for the future design of SQs.
We
suggest gelatin hydrogel as an electrolyte and demonstrate organic
electrochemical transistors (OECTs) based on a sheet of gelatin. We
also modulate electrical characteristics of the OECT with respect
to pH condition of the gelatin hydrogel from acid to base and analyze
its characteristics based on the electrochemical theory. Moreover,
we extend the gelatin-based OECT to electrochemical logic circuits,
for example, NOT, NOR, and NAND gates.
As one of conducting polymers, PEDOT:PSS, is commonly used in organic electronics, especially for bioelectronics due to its advantages such as high electrical and ionic conductivity, solution-processability and biocompatibility. Creating bioelectronics with the PEDOT:PSS requires advanced techniques to obtain physical/chemical modification of the PEDOT:PSS for improved performance and various applications. To satisfy these demands, fibrillary gelation of PEDOT:PSS by injection to choline acetate, an ionic liquid, with a constant flow rate was used in this study to make a conductive fiber and improve characteristics of PEDOT:PSS. Conductive fibers by fibrillary gelation showed enhanced electrical conductivity of about 400 S cm−1 and volumetric capacitance of about 154 F cm−3 which would be strongly beneficial to be utilized for organic electrochemical transistors (OECTs), resulting in a high transconductance of 19 mS in a depletion-mode. Moreover, dedoping of the conductive fibers by PEI (polyethyleneimine) enabled the creation of enhancement-mode OECTs. Interdigitated inverters were then fabricated by connecting depletion and enhancement-mode OECTs. These results demonstrate that these conductive fibers and electronic-textiles are suitable candidates for applications in bio-integrated electronics.
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