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Papertronics: Multigate paper transistor for multifunction applications
Publication . Martins, Rodrigo; Gaspar, Diana; Mendes, Manuel J.; Pereira, Luis; Martins, Jorge; Bahubalindruni, Pydi; Barquinha, Pedro; Fortunato, Elvira; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; Elsevier
The use of disposable recyclable, eco-friendly, sustainable and low-cost devices with multiple functions is becoming a demand in the emerging area of the Internet of Things as a way to decrease the degree of complexity of the electronic circuits required to serve a plethora of applications. Moreover, for low-cost disposable applications, it is relevant the systems to be recyclable. The idea beyond the present study concerns to exploit our imagination with simple questions such as: What happens if it is possible to have a simple and universal device architecture, easy to implement on paper substrates, but capable to provide different multiple functionalities? It would be possible to have a common template for electronic systems on paper that would be then easily customized depending on the final application? The present study answers to these demands by reporting the physics and electronics behavior of a multigate paper transistor where paper is simultaneously the substrate and the dielectric, while a metal-oxide-semiconductor (IGZO) is used as the active channel. Moreover, the same device is able to present logic functionalities simply by varying the amplitude and frequency of the input gate signals. These transistors operate at drain voltages of 1 V with low power, exhibiting ION/IOFF > 104 and a mobility ≈2 cm2 V−1 s−1, serving the specifications for a broad range of smart disposable low power electronics. To sustain all this, an analytical compact model was developed able to precisely reproduce the response of paper-based dual-gate FETs and provide full understanding of their unique and innovative operational characteristics.
E-Skin Bimodal Sensors for Robotics and Prosthesis Using PDMS Molds Engraved by Laser
Publication . Dos Santos, Andreia; Pinela, Nuno; Alves, Pedro; Santos, Rodrigo; Farinha, Ricardo; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Igreja, Rui; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; MDPI - Multidisciplinary Digital Publishing Institute
Electronic skin (e-skin) is pursued as a key component in robotics and prosthesis to confer them sensing properties that mimic human skin. For pressure monitoring, a great emphasis on piezoresistive sensors was registered due to the simplicity of sensor design and readout mechanism. For higher sensitivity, films composing these sensors may be micro-structured, usually by expensive photolithography techniques or low-cost and low-customizable molds. Sensors commonly present different sensitivities in different pressure ranges, which should be avoided in robotics and prosthesis applications. The combination of pressure sensing and temperature is also relevant for the field and has room for improvement. This work proposes an alternative approach for film micro-structuration based on the production of highly customizable and low-cost molds through laser engraving. These bimodal e-skin piezoresistive and temperature sensors could achieve a stable sensitivity of -6.4 × 10-3 kPa-1 from 1.6 kPa to 100 kPa, with a very robust and reproducible performance over 27,500 cycles of objects grasping and releasing and an exceptionally high temperature coefficient of resistance (TCR) of 8.3%/°C. These results point toward the versatility and high benefit/cost ratio of the laser engraving technique to produce sensors with a suitable performance for robotics and functional prosthesis.
A Voltage Controlled Oscillator Using IGZO Thin-Film Transistors
Publication . Keragodu, Tejaswini; Tiwari, Bhawna; Nishtha; Bahubalindruni, Pydi; Goes, Joao; Barquinha, Pedro; DEE2010-A2 Electrónica; CTS - Centro de Tecnologia e Sistemas; DEE - Departamento de Engenharia Electrotécnica e de Computadores; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)
This paper presents a voltage controlled oscillator (VCO) using amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs). This circuit consists of a high-gain OpAmp, a comparator and a relaxation oscillator. The implemented relaxation oscillator shows a power consumption of 700 μW, when it is simulated with a supply rail of ±5 V. It shows a frequency of oscillation range from 327 to 560 Hz, when the tuning capacitance value varies from 1.6 to 5 pF. On the other hand, the VCO has a power dissipation of 1.3 mW with frequency ranging from 400 to 556 Hz with a controlling voltage from -5 to 5 V. In-house oxide TFT model is used for circuit simulations in Cadence environment. This circuit finds potential applications in large-area flexible systems, namely smart packaging, biomedical and wearable systems, which needs clocks with different frequencies.
TiO2 nanostructured films for electrochromic paper based-devices
Publication . Nunes, Daniela; Freire, Tomas; Barranger, Andrea; Vieira, João; Matias, Mariana; Pereira, Sónia; Pimentel, Ana; Cordeiro, Neusmar J. A.; Fortunato, Elvira; Martins, Rodrigo; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; MDPI - Multidisciplinary Digital Publishing Institute
Electrochromic titanium dioxide (TiO2) nanostructured films were grown on gold coated papers using a microwave-assisted hydrothermal method at low temperature (80 °C). Uniform nanostructured films fully covered the paper substrate, while maintaining its flexibility. Three acids, i.e., acetic, hydrochloric and nitric acids, were tested during syntheses, which determined the final structure of the produced films, and consequently their electrochromic behavior. The structural characteristics of nanostructured films were correlated with electrochemical response and reflectance modulation when immersed in 1 M LiClO4-PC (lithium perchlorate with propylene carbonate) electrolyte, nevertheless the material synthesized with nitric acid resulted in highly porous anatase films with enhanced electrochromic performance. The TiO2 films revealed a notable contrast behavior, reaching for the nitric-based film optical modulations of 57%, 9% and 22% between colored and bleached states, at 250, 550 and 850 nm, respectively in reflectance mode. High cycling stability was also obtained performing up to 1500 cycles without significant loss of the electrochromic behavior for the nitric acid material. The approach developed in this work proves the high stability and durability of such devices, together with the use of paper as substrate that aggregates the environmentally friendly, lightweight, flexibility and recyclability characters of the substrate to the microwave synthesis features, i.e., simplicity, celerity and enhanced efficiency/cost balance.
Transduction mechanisms, micro-structuring techniques, and applications of electronic skin pressure sensors: A review of recent advances
Publication . Santos, Andreia Dos; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Igreja, Rui; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI - Multidisciplinary Digital Publishing Institute
Electronic skin (e-skin), which is an electronic surrogate of human skin, aims to recreate the multifunctionality of skin by using sensing units to detect multiple stimuli, while keeping key features of skin such as low thickness, stretchability, flexibility, and conformability. One of the most important stimuli to be detected is pressure due to its relevance in a plethora of applications, from health monitoring to functional prosthesis, robotics, and human-machine-interfaces (HMI). The performance of these e-skin pressure sensors is tailored, typically through micro-structuring techniques (such as photolithography, unconventional molds, incorporation of naturally micro-structured materials, laser engraving, amongst others) to achieve high sensitivities (commonly above 1 kPa−1), which is mostly relevant for health monitoring applications, or to extend the linearity of the behavior over a larger pressure range (from few Pa to 100 kPa), an important feature for functional prosthesis. Hence, this review intends to give a generalized view over the most relevant highlights in the development and micro-structuring of e-skin pressure sensors, while contributing to update the field with the most recent research. A special emphasis is devoted to the most employed pressure transduction mechanisms, namely capacitance, piezoelectricity, piezoresistivity, and triboelectricity, as well as to materials and novel techniques more recently explored to innovate the field and bring it a step closer to general adoption by society.
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5876
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147333