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Printed organic semiconductor devices on plastic substrates. (a) Schematic structure of the OTFTs and chemical structures of DTBDT-C6 and polystyrene (PS). (b) Photograph of the devices. (c) Cross-polarized optical microscope image of the OTFT channel. (d) Transfer curves and (e) output curves of the OTFT. (f) Optical microscope image and (g) circuit diagram of the pseudo-CMOS inverter. (h) Static input-output characteristics of the inverter. Output voltage (VOUT) and small-signal gain (|dVOUT/dVIN|) as a function of input voltage (VIN) at control voltages (VC) from 2 to 1.3 V in 0.1 V step. (i) Circuit diagram of the amplification unit with negative feedback. (j) VOUT and gain as a function of VIN with and without feedback. For the feedback, R2 is fixed at 1 GΩ, and R1 is varied from 100 to 300 MΩ.
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Electrochemical sensor systems with integrated amplifier circuits play an important role in measuring physiological signals via in situ human perspiration analysis. Signal processing circuitry based on organic thin-film transistors (OTFTs) have significant potential in realizing wearable sensor devices due to their superior mechanical flexibility a...
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... % dispersion in tripropylene glycol mono methyl ether (TPM) silver nanoparticle ink (Sigma-Aldrich, Merk, US) with a nominal particle size between D50 = 70 nm and D90 = 115 nm. TPM silver nanoparticleink is commonly used for printed PCB and has been used for antibacterial materials as well as large-scale applications[333][334][335].The printing process for the three DIW strain gauges are characterised and optimised for high-resolution printing (see Section 3.2.5.). These four strain gauges are then embedded in a 1 mm powder protective layer (see Section 3.2.6.), ...
Metal additive manufacturing (AM) techniques like laser powder bed fusion can print highly complex geometries, ideally with internal sensors. Depending on the component shape these internal sensors, may only be accessible and monitored from the outer surface of the component. Hence, placing or printing of the sensors inside the component requires the sensor to communicate information from outside with remote sensing. Ideally, sensors would be added during printing; however, during LPBF very high temperatures (> 3347℃) are reached causing thermal damage to sensors. Two sets of results are presented. Firstly, four sensors were successfully designed and embedded using two types of novel sensors. An embedding methodology was developed and validated for strain monitoring in Ti-6Al-4V components. A powder protective layer was introduced to prevent damaging the sensors during the laser scanning process. An optimal 1 mm powder protective layer was determined using computational analysis and validated through three-point flexural bench testing. A 1 mm powder protective layer was effective for the strain gauges that were printed using direct ink write (DIW) with glass fibre (GF) reinforced phenolic backing and tripropylene glycol diacrylate (TPGDA) backing. Surface roughness affects the mechanical performance and durability of LPBF components. The surface topology requirements also vary on component application. The evolution mechanisms of surface roughness during LPBF are not well understood due to a lack of in situ characterisation methods. Therefore, the second set of experiment focused on defect dynamics are quantified using synchrotron X-ray imaging and ex situ optical imaging and explain the evolution mechanisms of side-skin and top-skin roughness during multi-layer LPBF of Ti-6Al-4V. Then a surface topology matrix was developed that accurately describes surface features. The results suggest that the proposed process can open new avenues for LPBF technology to realise metal components with a self-cognitive ability using integrated sensors and highlight the need for hybrid smart manufacturing to meet the demands of multiple sectors e.g., biomedical and aerospace.
... The valinomycin-based K + -selective membrane was used to cover the active area of the carbon electrode via a PEDOT:PSS-based interfacial ion-electron transducer layer, which had the same structure as in our previous study. (32) The liquid-junction Ag/AgCl reference electrode composed of a Ag/AgCl electrode pattern covered with an internal electrolyte layer and an insulation layer was fabricated on the same substrate. The internal electrolyte layer was connected to the outer measurement solution through a nitrocellulose-membrane-based liquid junction. ...
... The OTFT device offers numerous advantages, including low cost, structural flexibility, and big-area fabrication based on a solution technique, but it is insufficient in performance uniformity and device stability [14][15][16]. As a result, the OTFT has the potential to be employed in a wide variety of applications, including electrophoretic displays, radio frequency identification (RFID), and biomedical sensors [17][18][19][20][21]. Furthermore, OTFTs may be used in the driving array of mini-LED backlight sources. ...
Ion-sensitive field-effect transistors (ISFETs) are used as elementary devices to build many types of chemical sensors and biosensors. Organic thin-film transistor (OTFT) ISFETs use either small molecules or polymers as semiconductors together with an additive manufacturing process of much lower cost than standard silicon sensors and have the additional advantage of being environmentally friendly. OTFT ISFETs’ drawbacks include limited sensitivity and higher variability. In this paper, we propose a novel design technique for integrating extended-gate OTFT ISFETs (OTFT EG-ISFETs) together with dual-gate OTFT multiplexers (MUXs) made in the same process. The achieved results show that our OTFT ISFET sensors are of the state of the art of the literature. Our microsystem architecture enables switching between the different ISFETs implemented in the chip. In the case of sensors with the same gain, we have a fault-tolerant architecture since we are able to replace the faulty sensor with a fault-free one on the chip. For a chip including sensors with different gains, an external processor can select the sensor with the required sensitivity.
... The detection of ion concentrations such as pH is vital for healthcare, environmental science, and sports monitoring [143,170]. Typical OFETs-based pH sensors need a large operation voltage of a few tens volts, leading to their limited use in low voltage operated and power-constrained portable sensing systems. ...
Organic field-effect transistors (OFETs) have been proposed beyond three decades while becoming a research hotspot again in recent years because of the fast development of flexible electronics. Many novel flexible OFETs-based devices have been reported in these years. Among these devices, flexible OFETs-based sensors made great strides because of the extraordinary sensing capability of FET. Most of these flexible OFETs-based sensors were designed for biological applications due to the advantages of flexibility, reduced complexity, and lightweight. This paper reviews the materials, fabrications, and applications of flexible OFETs-based biosensors. Besides, the challenges and opportunities of the flexible OFETs-based biosensors are also discussed.Graphical abstract
... Figure 6b shows the transistor's capability to be responsive to dopamine and in the presence of a variety of interference, have excellent selectivity. Finally, Shiwaku et al. [46] demonstrated a novel potentiometric electrochemical sensing system in terms of electrolyte ions (in Figure 6c-e). Lack of potassium ions in the human body results in symptoms such as muscle weakness, body fatigue, loss of appetite, and tachycardia. ...
Recently, people are becoming more concerned about their physical health and putting forward higher requirements for an early and painless diagnosis of diseases. Traditional methods, such as surface plasmon resonance (SPR), enzyme-linked immunosorbent assay (ELISA), surface-enhanced raman spectroscopy (SERS), and colorimetric methods have been used for the detection of biomarkers with high selectivity and sensitivity; however, these methods still need to be further improved for immediate and rapid diagnosis. Herein, organic thin-film transistors (OTFTs)-based biosensors offer the advantages of good flexibility, low-cost fabrication, reasonable sensitivity, and great biocompatibility for efficient determination of biomarkers in complex samples, including saliva, sweat, urine, and blood, respectively, exhibiting great potential in early disease diagnosis and clinical treatment.
... While amperometric measurement methods generally utilized for the monitoring glucose, and lactate levels in sweat, potentiometric measurement methods, specifically ISEs, are employed to detect potassium, sodium, and chloride ions [56]. Due to very low signal level in potentiometric sensors, an integrated sensing device with high input impedance amplifiers should be used to read them [76]. For example, Shiwaku et al. developed an innovative potentiometric-based electrochemical sensor that includes ISE-based potassium sensor and amplifier circuits that use organic thin-film transistor (OTFT)ebased pseudo-complementary metaleoxideesemiconductor (CMOS) inverters with highly controllable switching voltage and closed-loop gain [76]. ...
... Due to very low signal level in potentiometric sensors, an integrated sensing device with high input impedance amplifiers should be used to read them [76]. For example, Shiwaku et al. developed an innovative potentiometric-based electrochemical sensor that includes ISE-based potassium sensor and amplifier circuits that use organic thin-film transistor (OTFT)ebased pseudo-complementary metaleoxideesemiconductor (CMOS) inverters with highly controllable switching voltage and closed-loop gain [76]. Using printed OTFTbased pseudo-CMOS inverters, the sensitivity of the sensor was increased by a factor of 4.6 for the mentioned study. ...
... In another work by [82], a printed OTFT-based amplifier is utilized in a potentiometric electrochemical sensors since the signal levels from these sensors are typically very low i.e., a few hundred mV. The amplifier helps to amplify the low signal for better signal analysis. ...
... The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. May extend research on a fully integrated OTFTbased system [82] ...
Demand for organic electronics has growth tremendously for the past decade, owing to their high flexibility and low processing cost attributes. As part of the important elements in organic electronics, a solution processable organic thin film transistor (OTFT) has been center of discussion among researchers. The OTFT is recognized to bring electrical, mechanical, and industrial benefits to a broad range of new applications such as flexible displays, radio frequency identification (RFID) tags, as well as biosensors specifically for healthcare monitoring system. Despite of their great application demand and significant technology advancement, the OTFT devices demonstrate unstable electrical performances especially in their mobilities and threshold voltages. These drawbacks will hold the fully commercialization of the OTFT in the market. Thus, this paper comprehensively reviews the current status of the OTFT technologies, ranging from material, device, process, and integration, including improvement that have been done on mobilities and operating voltages. Besides that, this work discusses on the applicability of the OTFT in the biosensor applications dedicated for real-time healthcare monitoring purposes. This review paper therefore is expected to provide a critical analysis on OTFT developments, as well as recognize their research gaps to allow their fully commercialization in the near future.
... The resulting OPA circuit exhibited an open-loop gain of 4 under the power supply current of 100 nA. When applied to ion sensing, the signal can be amplified to improve the signal-noise ratio (SNR) of detection 89 . ...
Flexible electronics have suggested tremendous potential to shape human lives for more convenience and pleasure. Strenuous efforts have been devoted to developing flexible organic field-effect transistor (FOFET) technologies for rollable displays, bendable smart cards, flexible sensors and artificial skins. However, these applications are still in a nascent stage for lack of standard high-performance material stacks as well as mature manufacturing technologies. In this review, the material choice and device design for FOFET devices and circuits, as well as the demonstrated applications are summarized in detail. Moreover, the technical challenges and potential applications of FOFETs in the future are discussed.
... Innovation in agriculture has multiplied to a remarkable extent, however the growing difficulty of sustainability stipulates doable and advantageous solutions. The demand for food has elevated agricultural recreation ensuring in acquiring the smart farming practices [2]. Over the years, widespread farming and invasive farming techniques have reduced soil fertility, inducing an imbalance in soil nutrients and fertility. ...
... In recent years, the technology of fabricating electronic devices using printing methods (printed electronics) has attracted attention from the viewpoint of low cost and low environmental impact. Since printing technology can provide high-throughput fabrication of electric circuits on film substrates, various applications have been demonstrated, including electrochemical sensors of biomaterials [1,2], strain detection of infrastructure [3], and wearable sensory systems [4][5][6][7][8][9][10]. In particular, temperature detection is one of the main interests as a fundamental physical quantity in various fields. ...
In recent years, the use of printing methods to fabricate electronic devices (printed electronics) has attracted attention because of their low cost and low environmental impact. Printing technology enables the high-throughput fabrication of electrical circuits on film substrates, providing inexpensive personal healthcare devices to monitor health status in real-time. Temperature detection is one of the central concerns as a fundamental physical quantity in various fields. In 2013, a highly sensitive flexible thermistor was reported by formulating aqueous inks of nickel oxide nanoparticles for inkjet printing. However, the calcinating of the nickel oxide (NiO) layer required a high-temperature process of more than 200°C, which required expensive polyimide films with high heat resistance. It is necessary to promote further the development of low-temperature processes for printed thermistors to realize flexible NTC thermistors at low cost using printed electronics technology. In screen printing and inkjet printing, the definition of the ink pattern applied on the substrate changes due to spreading and coffee distortion phenomena, and the thickness between sensors becomes non-uniform, which is a structural consistency problem that can lead to variations in sensing performance. This study developed a printing and low-temperature calcinating method of NTC thermistors with a temperature-sensitive layer of nickel oxide by using reverse offset printing. The NTC thermistors were fabricated by printing a comb-like pattern of silver nanoparticles and a thin nickel oxide film on a glass substrate. In addition, the low-temperature formation of a nickel oxide layer by oxygen plasma treatment was investigated, and XPS was used to carry out compositional analysis of the surface. Together with the plasma-assisted calcinating, a flexible NTC thermistor formed on polyethylene terephthalate (PEN) film is demonstrated.
