Bioinspired Cilia Sensors with Graphene Sensing Elements Fabricated Using 3D Printing and Casting

Abstract

Sensor designs found in nature are optimal due to their evolution over millions of years, making them well-suited for sensing applications. However, replicating these complex, three-dimensional (3D), biomimetic designs in artificial and flexible sensors using conventional techniques such as lithography is challenging. In this paper, we introduce a new processing paradigm for the simplified fabrication of flexible sensors featuring complex and bioinspired structures. The proposed fabrication workflow entailed 3D-printing a metallic mold with complex and intricate 3D features such as a micropillar and a microchannel, casting polydimethylsiloxane (PDMS) inside the mold to obtain the desired structure, and drop-casting piezoresistive graphene nanoplatelets into the predesigned microchannel to form a flexible strain gauge. The graphene-on-PDMS strain gauge showed a high gauge factor of 37 as measured via cyclical tension-compression tests. The processing workflow was used to fabricate a flow sensor inspired by hair-like ‘cilia’ sensors found in nature, which comprised a cilia-inspired pillar and a cantilever with a microchannel that housed the graphene strain gauge. The sensor showed good sensitivity against both tactile and water flow stimuli, with detection thresholds as low as 12 µm in the former and 58 mm/s in the latter, demonstrating the feasibility of our method in developing flexible flow sensors.

Enhanced Mechanical and Thermal Properties of Stereolithography 3D Printed Structures by the Effects of Incorporated Controllably Annealed Anatase TiO2 Nanoparticles

“…Over the past few decades, additive manufacturing (3D printing) technology has shown a remarkable growth, which promises enormous potentialities and has gained a lot of interest from a diverse range of fields such as biomedical science and engineering [1][2][3], printing electronics [4], microfluidics [5], and aerospace composites [6]. 3D printing technology demonstrates the fabrication process, which facilitates the layer-by-layer structure formation from computer-aided design (CAD) data [7,8].…”

Recent Progress in 3D Printed Mold-Based Sensors

“…The resulting strain on the sensors reduced the electrical resistance due to the increase in the resultant distance between the electrodes, which as a result, led to the motion of polymer chains and IL. One of the advantages Another interesting work is related to the formation of bioinspired cilia sensors using 3D printing and casting techniques [50]. The technique involved 3D printing of a metallic mold containing complex features such as micropillar and microchannel, where PDMS and graphene nanoplatelets were cast and drop-cast respectively to form the desired features.…”

“…Finally, a conductive Sensors 2020, 20, 703 6 of 28 dispersion containing graphene, n-butyl acetate and ethanol was drop cast on the microchannel of the cantilever surface. Figure 2 [50] shows the schematic diagram of the fabrication process of the 3D printing and casting process. The fabricated prototypes showed an average gauge factor and sensitivity of 37 ± 1.7 and 30 mV/(ms −1 ).…”

“…The sensors were tested for respiratory exhalation and oscillatory flow stimuli in deionized water to determine their capability as strain and flow sensors, respectively. Schematic diagram of the fabrication process of the 3D printed molds and subsequent casting of the PDMS and graphene on the mold and microchannel, respectively [50]. Reproduced from Kamat, A.M.; Pei, Y.; Kottapalli, A.G. Bioinspired cilia sensors with graphene sensing elements fabricated using 3D printing and casting.…”

“…Schematic diagram of the fabrication process of the 3D printed molds and subsequent casting of the PDMS and graphene on the mold and microchannel, respectively[50]. Reproduced from Kamat, A.M.; Pei, Y.; Kottapalli, A.G. Bioinspired cilia sensors with graphene sensing elements fabricated using 3D printing and casting.…”