3D customized and flexible tactile sensor using a piezoelectric nanofiber mat and sandwich-molded elastomer sheets

Abstract

We developed a skin-conformal flexible sensor in which three-dimensional (3D) free-form elastomeric sheets were harmoniously integrated with a piezoelectric nanofiber mat. The elastomeric sheets were produced by polydimethylsiloxane (PDMS) molding via using a 3D printed mold assembly, which was adaptively designed from 3D scanned skin surface geometry. The mold assembly, fabricated using a multi-material 3D printer, was composed of a pair of upper/lower mold parts and an interconnecting hinge, with material properties are characterized by different flexibilities. As a result of appropriate deformabilites of the upper mold part and hinge, the skin-conformal PDMS structures were successfully sandwich molded and demolded with good repeatability. An electrospun poly(vinylidene fluoride trifluoroethylene) nanofiber mat was prepared as the piezoelectric active layer and integrated with the 3D elastomeric parts. We confirmed that the highly responsive sensing performances of the 3D integrated sensor were identical to those of a flat sensor in terms of sensitivity and the linearity of the input–output relationship. The close 3D conformal skin contact of the flexible sensor enabled discernable perception of various scales of physical stimuli, such as tactile force and even minute skin deformation caused by the tester’s pulse. Collectively from the 3D scanning design to the practical application, our achievements can potentially meet the needs of tailored human interfaces in the field of wearable devices and human-like robots.

Recent Advances of 4D Printing Technologies Toward Soft Tactile Sensors

“…Besides, because of the unique energy harvesting characteristics of piezoelectric materials, they are considered as a potential candidate for low-power or selfpowered tactile sensors. Lee et al (2017) fabricated a 3D customized STS. This piezoelectric-type mechanoelectrical sensor is mainly composed of sandwich-shaped substrates and a core piezoelectric layer.…”

Recent Progress in 3D Printed Mold-Based Sensors

“…These balloon fins in the presence of micro-fingers were able to reduce the stress concentrations that are highly probable for 2D structures to cause material failure. A 3D flexible tactile sensor was developed by Lee et al [56] by integrating a 3D printed PDMS molding with a nanofiber mat. This wearable device can be used to measure the tactile force and even skin deformation caused by the tester's pulse.…”

“…This researcher group also developed an algorithm to hold the object using its unique actuation mode. Lee et al [56] fabricated a flexible tactile sensor using piezoelectric nano-fiber using 3D printed mold assembly. A core piezoelectric layer and a lower and upper sandwiching substrate were used to fabricate this mechanical sensor.…”

Inducing Damage Diagnosis Capabilities in Carbon Fiber Reinforced Polymer Composites by Magnetoelastic Sensor Integration via 3D Printing

“…Magnetite/thermoplastic composite in 3D printing as direct replacements for commercially available flow sensors [12], or custom-built devices (whiskers) with built-in magnetostrictive materials for specific flow measuring applications [13] have been successfully manufactured. Magnetic force sensors [14], or devices for sensing human tactile force and imperceptible skin deformation due to heart pulses [15] for biomechanical applications are reported as feasible options for 3D printed smart objects. Specifically, some applications related to stretchable sensors for biomedical purposes are also reported in [16].…”