Hand‐Drawn Resistors, Capacitors, Diodes, and Circuits for a Pressure Sensor System on Paper

Abstract

containing silver, [11] metallic nanowires, [12] indium-gallium alloys, [13] or carbon nanotubes. [14] In addition, inks containing semiconductors such as zinc oxide [15] or poly-3-octylthiophene [16] have been developed. These materials have been used for the development of electrocardiogram sensors, [17] antennas, [18] displays, [19] and transistors. [20][21][22] Nevertheless, the complex synthesis required to produce such inks limits their widespread use. Graphite, on the other hand, is an abundant and cheap material, and lead pencils have been used to write on paper since the 16th century. [23] More importantly, due to the bulk structure of graphite, which consists of disorganized clusters of stacked graphene sheets connected by Van der Wall bonds, graphite is an electrically conductive material. Hence, commercially available pencils can be used to fabricate pencil-written electronic components, circuits, and sensors. [24][25][26][27][28] In this work, the complexity and functionality of hand-written electronics is moved to a new level through the development of a complete pressure sensor system which also features the first hand-written Schottky diode on paper. The presented system is based on a pen and pencil-written half-wave rectifier, as well as a low-pass filter and percolation force-sensitive resistor. It also includes an off-the-shelf operational amplifier biased using hand-written passive components. The amplifier acts as a sensor conditioning circuit and improves the signal-to-noise ratio of the device. The realization of the system relied on a detailed characterization of the discrete components to evaluate and define the fabrication parameters.Pencils containing different graphite-to-clay ratios allow for the fabrication of thin-film resistors with varied sheet resistances. Changing resistance values is easily achieved by either removing or adding graphite layers to or from the existing structures, making the prototyping process faster. Graphitepaper-graphite parallel plate capacitors demonstrate capacitance values as high as 141 pF cm −2 ; this is three times larger than similar existing paper capacitors. [29] Larger capacitances can only be reached utilizing high-k solutions such as sulfuric acid. [30] Hand-written Schottky diodes on paper exhibiting rectification ratios of 1:8 were also fabricated and studied. All handwritten devices are used to realize circuits including rectifiers and filters for frequencies up to 13.56 MHz. Finally, all presented devices and circuits were tested under tensile and compressive stress. Bending radii down to 100 µm (corresponding -written fabrication techniques offer new ways of developing customizable, biodegradable, and low-cost electronic systems. In this work, a new level of complexity is demonstrated for hand-written electronics by fabricating passive components, circuits, and a sensor system on paper. The system comprises a pencil-written graphite force-sensitive resistor, a pencil-drawn RC filter, a pen-written half-wave rectifier, and a commercial front...

A Simple, Low-Cost Micro-Coating Method for Accuracy Improvement and Its Application in Pressure Sensors

“…(5) This method has excellent performance in waterproofing, corrosion resistance, and biocompatibility. Therefore, this simple, efficient, and low-cost method for improving the accuracy of pressure sensors has desirable application prospects in industrial production [32,33], biochemical detection, medical diagnosis [34], marine exploration [35], environmental protection, experimental testing, and other industrial automation. This method should also be useful for improving the accuracy of other kinds of sensors.…”

Flexible Sensors—From Materials to Applications

“…The combination of its high carrier mobility (as high as 20,000 cm 2 V -1 S -1 for electrons on a graphene field effect transistor (FET) [83]), with the ability to sustainably conduct high currents (>1 × 10 8 A/cm 2 ), made this material very attractive for the development of thin film transistors [84,85], battery electrodes [86], and sensors [87]. In the field of flexible electronics, carbon-based materials have found most of their applications as electrical conductors and can be found in various formats including CNTs [88,89], CNT fibres [90][91][92], graphene [93][94][95][96], reduced graphene oxide (rGO) [97][98][99], carbon black (CB) [100,101] and graphite [102][103][104][105]. Graphene is a 2D material that presents both the properties of a conductor and a semiconductor [106].…”

“…Although the current trend shows interest into materials microengineering, a traditional strain-gauge based resistive pressure sensor made of Ni-Cr on a PI substrate exhibited a broad detection range in between 6.25 × 10 -3 kPa to 930 kPa, a sensitivity of 16.6 %/kPa for pressure values above 380 kPa, and a response time of 20 ms [7]. A more exotic example of flexible electronics comes from the fabrication on-paper of complex electronic circuits in which its components are fabricated on a paper substrate using various pencils and inks, and an FSR consists of two stacked graphite contacts separated by a ring-shaped paper spacer [102]. Overall the sensor showed a low detection limit of 0.2 kPa and a high detection limit of 1.2 kPa.…”

Low Temperature and Radiation Stability of Flexible IGZO TFTs and their Suitability for Space Applications

“…To apply this semiconductor on space wearable applications, its suitability and stability must be assessed. While the mechanical stability of a-IGZO has already been extensively studied by demonstrating outstanding bending stability down to 25 µm bending radii [6]- [9], low temperature, and electron irradiation stress is equally important for space applications. Previously, it was shown that rigid a-IGZO transistors continue to operate after being exposed to relatively low energetic electron irradiation (0.8 MeV -10 14 e -/ cm 2 ) [10].…”