3D Printing of a Flexible Inclined‐Tip Cone Array‐Based Pressure Sensor

Abstract

particularly important for the detection of physiological signals. To improve the high sensitivity performance of pressure sensors, some researchers have designed special microstructure shapes-that is, pyramids, [16][17][18] ciliated microarrays, [19] inclined micropillars, [20] and convex microarrays. [21][22][23][24] Luo et al. designed a tilted micropillar structure to act as the dielectric layer of a pressure sensor using photolithography technology, [20] and improved the sensitivity of the pressure sensor by 0.42 kPa −1 through bending deformation of the tilted micropillar. Xiong et al. sputtered a gold layer microarray on a film to form a polydimethylsiloxane-gold (PDMS-Au) electrode, and placed a polyvinylidene difluoride (PVDF) film in the middle layer of the electrode to form a pressure sensor with a sandwich structure and a sensitivity of 30.2 kPa −1 . [25] Guan et al. converted natural wood into graphene-oxide-modified flexible wood through a sawing process and chemical treatment, obtaining an environmentally friendly wood pressure sensor with a sensitivity of 1.85 kPa −1 . [26] Sun et al. proposed a flexible fish-scale structure based on a PDMS/carbon nanotube (CNT) composite material, [27] the tactile electronic skin sensor developed with a high sensitivity of 12.1 kPa −1 . Although a variety of microstructure designs have improved sensor pressure sensitivity, when dealing with high pressures (>50 kPa), a single microstructure design can cause a pressure sensor to suffer from limited or saturated pressure response. This is because high-pressure sensors are not considered in the design of multi-level structures to increase the pressure test range of a sensor. [28] Moreover, they require expensive equipment and complex manufacturing processes. Consequently, pressure sensors that are designed with high sensitivity and undergo pressure testing over a wide range will become an important research topic for future studies.In this study, we used PDMS as a flexible carrier and added several conductive materials-such as carbon black (CB), CNTs, and nano-copper powder-to prepare conductive inks suitable for 3D printing. [29][30][31] To detect a wide range of pressures, the inclined-tip cone array of a flexible pressure sensor's conductive layer was designed as a three-layered structure with a stepped height. Inclined cone arrays of different heights produced more sensitive bending over a low-pressure detection range. UnderThe high sensitivity and portability of flexible pressure sensors have attracted widespread attention from researchers owing to their potential use in health monitoring and exercise detection applications. However, to improve the performance of pressure sensors, a special microstructure-shaped design is necessary, which usually requires a complicated manufacturing process. In this study, the use of 3D printing technology is proposed to develop a polydimethylsiloxane-based material along with several conductive materials-carbon black, multiwalled carbon nanotubes, and copper mixed conductive in...

Functional microneedles for wearable electronics

“…With the aid of these advanced sensors, people can get reliable and real-time information about joint motions such as bending of knuckles, elbows, and knees, gaits such as jumping, walking, and standing, as well as facial expressions such as speaking, 10C-F). 72 To be specific, the detection range, sensitivity, response time, and detection limit of this sensor were 0-396 kPa, 212 kPa −1 , 32 ms and 7.69 Pa, respectively. Besides, after 5000 compression cycles, such sensors still showed high stability and consistency.…”

“…poly (3,4ethylenedioxythiophene): poly(styrenesulfonate), 67 gold nanowires, 68 MXene nanoflakes 69 and carbon black 70 ) or mingled with conductive substances (e.g. carbon nanotube, 71 carbon black 72 and nano-copper 72 ) is usually used to constitute the microneedle-like layers. Up to now, researchers have applied the resistance-based sensors to monitor wrist pulse, 68 recognize voice, 69 detect body movements 72 and so on.…”

“…carbon nanotube, 71 carbon black 72 and nano-copper 72 ) is usually used to constitute the microneedle-like layers. Up to now, researchers have applied the resistance-based sensors to monitor wrist pulse, 68 recognize voice, 69 detect body movements 72 and so on. For example, a microneedleintegrated electronic skin was presented for sensing both pressure and strain forces (Figure 4A).…”

“…Besides, after 5000 compression cycles, such sensors still showed high stability and consistency. 72 Furthermore, microneedle-integrated wearable sensors can contribute a lot to detecting pulse waves, breathing, blood oxygen, and many other biophysical signals. For instance, a resistance-based sensor had the ability to record pulse waves in real time and obtain pulse information, such as vibration intensity, characteristic peaks, and periods (Figure 10G).…”

Development of Pressure Sensor Based Wearable Pulse Detection Device for Radial Pulse Monitoring

“…Apart from sensing material, the structural design of the device also has an important influence on the sensing performance of pulse detection devices. To improve the sensitivity, structural design of pressure-sensing-based pulse detection devices have been conducted, such as using micro-pyramids [ 26 ], micro-pillars [ 27 ], and nano-cones [ 28 ] as the sensing structures. For instance, Bao et al [ 29 ] proposed a tunable method of designing pyramid micro-structured pressure sensors for target sensing requirements, and the fabricated pressure sensors with specialized pyramid microstructures can be applied to the arterial pulse waves detection.…”