All Digital Light Processing‐3D Printing of Flexible Sensor

Abstract

conductivity and immunity to deformations, as well as a robust interface between them for long-term usage. In addition, a facile, cost-effective, and eco-friendly fabrication method is highly desirable for the whole flexible sensor.Among a variety of fabrication methods reported so far, lithography, [16][17][18][19] screen printing, [20][21][22][23][24] inkjet printing, [25][26][27][28][29] and electroless deposition, [30,31] are widely used in flexible sensor fabrication. However these 2D fabrication methods only can fabricate flexible sensor on a flat plane. 3D printing, also called additive manufacturing, provides a rapid prototyping strategy for industrial design, architecture, aerospace, dental and medical industries, and other fields. [32] Due to the ability to fabricate components and structures rapidly, cost-efficiently, and environmentally, in recent years, 3D printing has been explored for the fabrication of flexible sensor for electronics. [33] Up to now, 3D printing technologies used in the fabrication of flexible sensor include fused deposition modeling (FDM), [34][35][36][37][38] direct ink writing (DIW), [39][40][41] and digital light processing (DLP). [42][43][44][45] Li et al. developed a FDM-3D printed flexible strain sensor based on carbon black/thermoplastic polyurethane, and periodic configurations were designed to improve the flexibility of sensing unit. [46] Hensleigh and coworkers fabricated a flexible 3D capacitive sensor based on multi-material DIW-3D printing, which can be integrated into prosthetic and soft robotic. [47] Despite of these successful studies, extrusion-based 3D printing techniques typically suffer from limited raw materials, easy clogging of the needles, and nonuniformity of the printed layers. [48] The stereolithography-based 3D printing technique, DLP-3D printing, relying on layer-by-layer curing of photocurable resin, has high resolution, simple process, and fast forming speed. Technically, DLP 3D printing of flexible sensor can be divided into two routes. The first one is to 3D printing of molds or substrates, then active components are filled into the molds or deposited on the substrates to form flexible sensors. For instance, Wu's group report a flexible pressure sensor with porous structure used DLP-3D printed hydrolysable scaffold as sacrificial mold which need to be dissolved to create the porous structure for sensing unit after curing the conductive polymer composites. [49] Xia and coworkers fabricated a flexible pressure sensor by 3D-printing of microstructured substrate with gold film spray-coated on it. [50] The second route for DLP-3D Flexible sensor with high sensitivity, high durability, and facile fabrication process has promising applications in structural health monitoring, humanmachine interface, and soft robotics areas. Digital light processing-3D (DLP-3D) printing can print flexible sensor in a scalable process. However, to achieve all DLP-3D printing of flexible sensor, there still exist challenges of how to print sensing units with high sensitivit...

Recent advances of additively manufactured noninvasive kinematic biosensors

“…Solid-type sensors exhibited a sensitivity of 1.62 MPa -1 under the pressure of 78.4 kPa. However, the woodpile structured sensor showed a sensitivity of 15.04 MPa under pressure of 64.44 kPa (Figure 3C) (Xiao et al, 2023).…”

“…Generally, a resistive sensor comprises a pair of electrodes encapsulating a conductive substance. The sandwiched material is functionalized with conductive properties by encompassing materials like carbon-based fillers (Wang et al, 2021;Xiao et al, 2023), metal fillers, metal-coated particles (Lo et al, 2020), conductive polymers (Liu et al, 2019), and hybrid fillers (Zhao C. et al, 2020). The fundamental principle underlying resistive sensors involves detecting kinematic stimuli through quantifying resistance changes when the mechanical stimulus is exerted.…”

Digital Light Processing‐3D Printing of Thermoset Materials with High Biodegradability from Amino Acid‐Derived Acrylamide Monomers

“…The previously reported materials are examples of a photocured compound via free radical polymerization. In the last decade, there was an explosion of novel materials and applications of SLA and DLP printed objects, [17,18] because the complexity and resolution of the printed pieces with these techniques are among the best compared to other 3D printing techniques. [19] Unfortunately, the biodegradability of polyether polymers is not so high as in the case of polyesters (such as poly(lactic acid), PLA, poly(lactic-co-glycolic acid), PLGA, or poly(caprolactone), PCL, polymers).…”

Mold‐Free Manufacturing of Highly Sensitive and Fast‐Response Pressure Sensors Through High‐Resolution 3D Printing and Conformal Oxidative Chemical Vapor Deposition Polymers

“…However, studies on 3D printing-based pressure sensors are limited in the literature because the printing technique with a resolution comparable to photolithography has not yet been established. Extrusion-based 3D printing processes are commonly used to fabricate functional sensors [31,32,[43][44][45][46][47] and 3D-printed mold by replacing Si, [48] due to the easy deposit of multiple materials. However, the resolution of extrusion-based 3D printing is determined by the nozzle size, typically larger than 100 μm.…”