Waterproof, thin, high-performance pressure sensors-hand drawing for underwater wearable applications

Figures & data

Figure 1. The figure of (a) Sensor fabrication process, (b) Top and bottom side of the sensor, (c) SEM picture of the pyralux film after etching-solution, (d) SEM picture of the sensing layer (wet-tissues) before coated by CNTs, (e) SEM pictures of the sensing layer (wet-tissues) after coated by CNTs

Figure 2. (a) Working principle of the sensor, (b) I–V curves at the different pressures from −5 V to 5 V, (c) Pressure–resistance relationship at the different pressures, (d) Relative resistive change as a function of pressure, showing the sensitivity of the sensor

Figure 3. (a) Response-relaxation time, (b) Resistance change at the different frequencies from 0.1 Hz to 5 Hz, (c) Durability of the sensor after 5,000 loading/unloading cycles

Figure 4. (a) The sensor underwater, (b) Schematic of the testing circuit, (c) Signal change with applied pressure underwater and no-water, (d) Touch signal of the sensor when immersed in the water

Table 1. Summarizes flexible sensors – based on hand-drawing/papers

Materials/Components	Type of sensor	Principle	Range	Sensitivity	Thickness	Response/Relaxation time	Hand drawing	Waterproof	Ref.
Cellulose paper, PDMS, Graphite (Pencil), ITO NPs	Bending	Resistive	-	-	< 140 µm	-	Yes	No	[37]
Cellulose paper, Graphite (Pencil)	Temperature, Biochemical,Electrophysiological	Resistive	-	-	< 110 µm	-	Yes	No	[40]
Copying tissue paper, Graphite (Pencil), GO & fiber foam	Pressure	Capacitive	0–50 kPa	~ 0.14 kPa^−1	~ 110 µm	180/120 ms	Yes	No	[41]
Cellulose paper, Graphite (Pencils), Silver ink, Nickel ink, IGZO semiconductor	Pressure, Op-amp	Resistive	0–1.2 kPa	~ 0.05 kPa^−1	-	-	Yes	No	[42]
Cellulose paper, Conductive brush pen	Strain	Resistive	-	< 0.001 kPa^−1	~ 150 µm	-	Yes	No	[46]
Post-it paper, Silver ink pen, Graphite (Pencil), Aluminum foil, Microfiber Wipe, Sponge	Pressure/Temperature/Humidity/PH	Resistive/Capacitive	-	0.16 kPa^−1	-	-	Yes	No	[47]
Airlaid paper, Carbon black, Copper tape, Semipermeable film	Pressure	Resistive	0–30 kPa	> 7.12 kPa^−1	-	200 ms	No	Yes	[48]
Graphite (Pencil), Polyester substrate	Electrodes	-	-	-	-	-	Yes	No	[49]
Cellulose paper, Graphite (Pencil)	UV, Pressure, Chemical, Glucose	Resistive	-	~ 0.009 kPa^−1	-	-	Yes	No	[50]
Flexible film (pyralux), Permanent marker pen, Wet-tissues, CNTs	Pressure, Resistor	Resistive	0–45 kPa	0.2 kPa^−1 (0–6 kPa), 0.05 kPa^−1 (> 8 kPa)	~ 260 µm	50/70 ms	Yes	Yes	Ours

Figure 5. (a) Taking a photo on phone when dipping the sensor underwater, (b) Sensor integrated into the mask, (c) Breathing signal

Figure 6. (a) Structure of the matrix sensing layer, (b) Signal change of the matrix layer when applied an object, (c) Schematic of the hand-drawing circuit, (d) Real picture of the hand-drawing circuit, (e) Hand-drawing circuit when working underwater

Figure 7. (a) The experimental diagram to control music on phone, (b) Signal of each touch action, (c) Controlling commands corresponding to touch actions, (d) Structure of the autoencoder model, (e) Confusion matrices of the training data and testing data

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