In this work, we present an alternative system to standard microelectrode arrays for monitoring the electrical activity of 3D cellular aggregates such as neurospheroids, which are known to better replicate the complex architecture and cellular interactions of native neural tissue than 2D cultures. The system is based on an ultra-sensitive organic sensor called Organic Charge-Modulated Field Effect Transistor (OCMFET) fabricated through low-resolution, low-cost fabrication techniques. This peculiar organic charge sensor offers interesting features like the absence of a reference electrode in the culture medium, a direct charge amplification, mechanical flexibility, and optical transparency. As a preliminary validation, the OCMFET system has been coupled to rtTA/Ngn2-positive human induced pluripotent stem cell (hiPSC)-derived neurospheroids and was able to reliably detect their spontaneous electrical activity exhibiting a high SNR. This preliminary validation lays the foundation for the development of simple, low-cost, and ultra-flexible organic transistor-based systems for high-performing, reliable interfacing with 3D neuronal structures.

In this study, we present the development of an advanced multivariable sensing platform that combines a flexible extended-gate organic thin-film transistor (ExG-OTFT) with a surface plasmon resonance (SPR) readout of its sensing surface. This device architecture overcomes the limitations of prior combined SPR and field-effect transistor (FET)-based systems, thanks to the spatial separation of the sensing surface from the transistor body, and the implementation of a pseudo-reference electrode, which significantly improves the system reliability. We demonstrate the potential of this solution through the simultaneous electrical and optical detection of layer-by-layer formation of polyelectrolyte multilayers in real-time. While the SPR-based transduction is sensitive to local refractive index changes associated with a mass uptake on the sensing surface, the electronic transduction provides complementary information about collective charge carrier distribution. The ExG-OTFT architecture ensures compatibility with commercially available SPR instrumentation, enabling straightforward upgrades to SPR/FET functionality with minimal modifications. More interestingly, we introduce a flexible SPR/FET sensor, offering a scalable, robust and cost-effective solution (thanks to the use of convenient printing techniques for the fabrication of the organic FET) for multivariable sensing applications across diverse fields to advance the next generation of sensing platforms.

Electroencephalography (EEG) is a non-invasive electrophysiological measurement that plays a pivotal role in diagnosing neurological disorders. Apart from the clinical use, EEG gained progressive attention in the assessment and recognition of emotional states, the development of noninvasive human-machine interfaces, and for biofeedback. In such contexts, the development of innovative bioelectrodes, able to improve comfort and unobtrusiveness, fabricated by means of scalable, large-area fabrication techniques, is an important research goal. Herein, we present a novel approach for the fabrication of EEG textile bioelectrodes, which are based on large-area, spray coated poly(3,4-ethylenedioxythiophene) polystyrene sulfonate conductive polymer, mixed with an ionic additive. The bioelectrodes exhibit comparable performance with a commercial wearable device for EEG signal acquisition (i.e., the MuseT headset), when analyzing the EEG power spectral density during both eyes closed and eyes open conditions. These results suggest that the proposed textile electrodes could be an efficient alternative to state-of-the- art EEG electrodes, particularly in applications where unobtrusive and comfortable sensing is required.

Acquiring biopotentials from the surface of the body is a common procedure both in the clinical practice and in non-clinical applications as sport and human- machine interfaces. To avoid bulky recording systems and to allow optimal long-term measurements, several tattooable solutions were recently developed, aiming at high-quality and imperceptible electrodes. However, a seamless connection with epidermal electrodes still represents one of the biggest challenges in this field. In this paper, we propose a simple and efficient approach for the fabrication of free-standing epidermal electrodes that can be contacted using small magnetic connectors, thus directly tackling this issue. The proposed electrodes are fabricated using a conductive ink based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) deposited by spray coating, and can be easily contacted using magnetic connectors without disrupting their conformability, thanks to the presence of ferrite nanoparticles integrated within the thin film itself. These electrodes have been successfully employed for the detection of different biopotentials, namely electrocardiogram, electromyogram and electro-oculogram, demonstrating excellent performances for the detection of biosignals from delicate body parts, such as the face, thus demonstrating the effectiveness of the approach for the development of a new generation of magnetically connectable epidermal electrodes for critical biopotentials monitoring.

Organic biosensors are a class of devices specifically designed for the detection and quantification of bioanalytes and/or chemical-physical parameters whose variations occur within a biologically relevant environment. They provide the electronic transduction of chemico-physical properties by means of devices that, thanks to the peculiar properties (i.e., mechanical flexibility, ionic conductance) of organic materials, are biocompatible in a very broad sense, i.e., not only safe for biological tissues but also because they share with them a complete material affinity. For this reason, they are revolutionizing the world of biosensors, paving the way to a variety of novel tools for applications including electrophysiology, bioanalytical chemistry, brain-machine interfaces.

In this paper, the development of a simple and reproducible approach for the fabrication of n‐type organic field‐effect transistors with a 350 nm‐long channel on flexible substrates is reported. The critical feature of the device, the channel length, is obtained using a self‐alignment process that exploits the vertical step of a plasma‐etched thin Parylene C layer, according to the so‐called step‐edge architecture. The fabricated devices can operate in continuous mode and show an average and maximum transition frequency of 2.5 MHz and 5.5 MHz, respectively. The possibility of easily obtaining high‐performing, short channel organic transistors on flexible substrates, without the use of expensive and high‐resolution techniques, represents an interesting step toward the miniaturization of flexible circuits in the field of large‐area organic electronics.

: In this work, we present a prototype of a smart technical underwear for first responders involved in search-and-rescue operations, to be worn under the rescuer’s professional uniform. Polymer-based electrodes able to detect ECG and EMG signals, and organic transistor for joint angles estimation are embedded into the smart garment. The technical underwear implements a body sensor network of BLE nodes able to acquire, process in real-time and transmit electrophysiological and biomechanical data from the sensors to a custom Android app on the rescuer’s smartphone. The app geolocates the data by using the information of the GPS integrated into the smartphone and sends them to the control center for remote monitoring. The system features high modularity, as the rescuer can adopt a subset of sensors depending on the specific operative context, without any app configuration.

In an increasingly interconnected world, where electronic devices permeate every aspect of our lives, wearable systems aimed at monitoring physiological signals are rapidly taking over the sport and fitness domain, as well as biomedical fields such as rehabilitation and prosthetics. With the intent of providing a novel approach to the field, in this paper we discuss the development of a wearable system for the acquisition of EEG signals based on a portable, low-power custom PCB specifically designed to be used in combination with non-conventional ultra-conformable and imperceptible Parylene-C tattoo electrodes. The proposed system has been tested in a standard rest-state experiment, and its performance in terms of discrimination of two different states has been compared to that of a commercial wearable device for EEG signal acquisition (i.e., the Muse headset), showing comparable results. This first preliminary validation demonstrates the possibility of conveniently employing ultra-conformable tattoo-electrodes integrated portable systems for the unobtrusive acquisition of brain activity.

In this manuscript, we report on a novel architecture for the fabrication of highly sensitive multimodal tactile transducers, for the simultaneous detection of temperature and force. Such devices are based on a flexible Organic Charge Modulated Field Effect Transistor (OCMFET) coupled with a pyro/piezoelectric element, namely a commercial film of poly-vinylene difluoride (PVDF). The reduction of the channel length, obtained by employing a low-resolution vertical channel architecture, allowed to maximize the ratio between the sensing area and the transistor’s channel area, a technological approach that allows to considerably enhance both temperature and force sensitivity, while at the same time minimize the sensor’s dimensions. Thanks to the employment of a straightforward, up-scalable, and highly reproducible fabrication process, this solution represents an interesting alternative for all those applications requiring high-density, high-sensitivity sensors such as robotics and biomedical applications.

A breathable tattoo electrode for bio-potential recording based on a Parylene C nanofilm is presented in this study. The proposed approach allows for the fabrication of micro-perforated epidermal submicrometer-thick electrodes that conjugate the unobtrusiveness of Parylene C nanofilms and the very important feature of breathability. The electrodes were fully validated for electrocardiography (ECG) measurements showing performance comparable to that of conventional disposable gelled Ag/AgCl electrodes, with no visible negative effect on the skin even many hours after their application. This result introduces interesting perspectives in the field of epidermal electronics, particularly in applications where critical on-body measurements are involved.

In this manuscript we report about a novel concept for the fabrication of highly sensitive, flexible force sensors. The proposed devices have been fabricated on a flexible plastic substrates, using an Organic Charge Modulated Field Effect Transistor configuration. The transistor-based sensor is characterized by a floating gate coupled with a Piezoelectric material, namely PVDF. The main step forward in this work consists of the employment of short channel OTFT, fabricated by means of an easy, up-scalable and highly reproducible process, allowing to achieve a much higher sensitivity of the final device. Such an approach could be useful for all those applications in which high device density and high sensor sensitivity is required.

The past decade has been characterized by an impressive surge of wearable electronics devices for biopotential recording applications. Due to its important potential impact, the recording of EEG (electroencephalography) signals recently raised considerable interest within this new paradigm of human-electronics interfacing. Ideally, this application would require minimally-invasive wearable acquisition devices and highly comfortable recording electrodes, two important and complex features that have not been completely resolved. The main problems concerning the implementation of a wearable electronic system for EEG recordings are thus related, on one hand, to the processing/acquisition electronic board and, on the other hand, to the employed acquisition electrodes and their contact with the skin. In particular, the readout electronics for this application should be low-power and possibly easy to integrate in a wearable system, while the electrodes should be as imperceptible as possible, thus allowing comfortable long-term acquisitions. With the intent of providing an efficient solution to both issues, we propose a a very low size and weight (13x15x2cm, 46g), low power, with estimated battery duration of 28h, wearable electronic system for EEG monitoring that has been preliminary validated by the means of ultra-conformable epidermal electrodes.

In vitro electrogenic cells monitoring is an important objective in several scientific and technological fields, such as electrophysiology, pharmacology and brain machine interfaces, and can represent an interesting opportunity in other translational medicine applications. One of the key aspects of cellular cultures is the complexity of their behavior, due to the different kinds of bio-related signals, both chemical and electrical, that characterize these systems. In order to fully understand and exploit this extraordinary complexity, specific devices and tools are needed. However, at the moment this important scientific field is characterized by the lack of easy-to-use, low-cost devices for the sensing of multiple cellular parameters. To the aim of providing a simple and integrated approach for the study of in vitro electrogenic cultures, we present here a new solution for the monitoring of both the electrical and the metabolic cellular activity. In particular, we show here how a particular device called Micro Organic Charge Modulated Array (MOA) can be conveniently engineered and then used to simultaneously record the complete cell activity using the same device architecture. The system has been tested using primary cardiac rat myocytes and allowed to detect the metabolic and electrical variations thar occur upon the administration of different drugs. This first example could lay the basis for the development of a new generation of multi-sensing tools that can help to efficiently probe the multifaceted in vitro environment.

Interfacing ultrathin functional films for epidermal applications with external recording instruments or readout electronics still represents one of the biggest challenges in the field of tattoo electronics. With the aim of providing a convenient solution to this ever-present limitation, in this work we propose an innovative free-standing electrode made of a composite thin film based on the combination of the conductive polymer PEDOT:PSS and ferrimagnetic powder. The proposed epidermal electrode can be directly transferred onto the skin and is structured in two parts, namely a conformal conductive part with a thickness of 3 μm and a ferrimagnetic-conductive part that can be conveniently connected using magnetic connections. The films were characterized for ECG recordings, revealing a performance comparable to that of commercial pre-gelled electrodes in terms of cross-spectral coherence, signal-to-noise ratio, and baseline wandering. These new, conductive, magnetically interfaceable, and free-standing conformal films introduce a novel concept in the domain of tattoo electronics and can set the basis for the development of a future family of epidermal devices and electrodes.

Objective. Wearable devices have created new opportunities in healthcare and sport sciences by unobtrusively monitoring physiological signals. Textile polymer-based electrodes proved to be effective in detecting electrophysiological potentials but suffer mechanical fragility and low stretch resistance. The goal of this research is to develop and validate in dynamic conditions cost-effective and easily manufacturable electrodes characterized by adequate robustness and signal quality. Methods. We here propose an optimized screen printing technique for the fabrication of PEDOT:PSS-based textile electrodes directly into finished stretchable garments for surface electromyography (sEMG) applications. A sensorised stretchable leg sleeve was developed, targeting five muscles of interest in rehabilitation and sport science. An experimental validation was performed to assess the accuracy of signal detection during dynamic exercises, including sit-to-stand, leg extension, calf raise, walking, and cycling. Results. The electrodes can resist up to 500 stretch cycles. Tests on five subjects revealed excellent contact impedance, and cross-correlation between sEMG envelopes simultaneously detected from the leg muscles by the textile and Ag/AgCl electrodes was generally greater than 0.9, which proves that it is possible to obtain good quality signals with performance comparable with disposable electrodes. Conclusions. An effective technique to embed polymer-based electrodes in stretchable smart garments was presented, revealing good performance for dynamic sEMG detections. Significance. The achieved results pave the way to the integration of unobtrusive electrodes, obtained by screen printing of conductive polymers, into technical fabrics for rehabilitation and sport monitoring, and in general where the detection of sEMG in dynamic conditions is necessary.

In this chapter, we will focus on the recent developments within the very promising, and fairly new field of wearable, flexible, and organic (bio)electronics. A deep analysis of the most interesting devices and systems that have provided significant advances within biomedical fields such as biomechanics, clinical electrophysiology, and bioelectronics will be also provided, in order to tackle the newest approaches and techniques that are driving us toward a seamless, easier, and more "imperceptible" interaction with the human body.

Modern electrophysiology has been constantly fueled by the parallel development of increasingly sophisticated tools and materials. In turn, discoveries in this field have driven technological progress in a back-and-forth process that ultimately determined the impressive achievements of the past 50 years. However, the most employed devices used for cellular interfacing (namely, the microelectrode arrays and microelectronic devices based on transistors) still present several limitations such as high cost, the rigidity of the materials, and the presence of an external reference electrode. To partially overcome these issues, there have been developments in a new scientific field called organic bioelectronics, resulting in advantages such as lower cost, more convenient materials, and innovative fabrication techniques. Several interesting new organic devices have been proposed during the past decade to conveniently interface with cell cultures. This paper presents the protocol for the fabrication of devices for cellular interfacing based on the organic charge modulated field-effect transistor (OCMFET). These devices, called micro OCMFET arrays (MOAs), combine the advantages of organic electronics and the peculiar features of the OCMFET to prepare transparent, flexible, and reference-less tools with which it is possible to monitor both the electrical and the metabolic activities of cardiomyocytes and neurons in vitro, thus allowing a multiparametric evaluation of electrogenic cell models.