The 3D Printing of Nanocomposites for Wearable Biosensors: Recent Advances, Challenges, and Prospects

Abstract

Notably, 3D-printed flexible and wearable biosensors have immense potential to interact with the human body noninvasively for the real-time and continuous health monitoring of physiological parameters. This paper comprehensively reviews the progress in 3D-printed wearable biosensors. The review also explores the incorporation of nanocomposites in 3D printing for biosensors. A detailed analysis of various 3D printing processes for fabricating wearable biosensors is reported. Besides this, recent advances in various 3D-printed wearable biosensors platforms such as sweat sensors, glucose sensors, electrocardiography sensors, electroencephalography sensors, tactile sensors, wearable oximeters, tattoo sensors, and respiratory sensors are discussed. Furthermore, the challenges and prospects associated with 3D-printed wearable biosensors are presented. This review is an invaluable resource for engineers, researchers, and healthcare clinicians, providing insights into the advancements and capabilities of 3D printing in the wearable biosensor domain.

Keywords: 3D printing; biomedical; health monitoring; nanocomposites; wearable biosensors.

Figure 1

The development timeline of wearable biosensor devices: (a) GlucoWatch; (b) NFC-approved sensors; (c) nanowire-based electronic skin; (d) Qi standard established sensors; (e) Bluetooth mouthguard sensors; (f) TEG (thermoelectric generator) wristbands; (g) Bluetooth 5 sensors; (h) thermo-responsive microneedle devices; (i) multiplexed flexible epidermal sensors; (j) fully integrated smart wristbands; (k) first mobile processing unit with a neural engine; (l) sweat collection reservoir, wearable microfluidic sensing patch; (m) 5G began deployment; (n) flexible battery-free NFC epidermal sensors; (o) TENG-based Bluetooth sweat sensors; (p) wearable salivary glucose Bluetooth biosensors; (q) AI-enabled multiplexed epidermal mental-fatigue-monitoring biosensors; (r) biofuel-powered Bluetooth sweat sensors; (s) SVM-empowered differential cardiopulmonary monitoring sensors; (t) AI-enabled biosensors, © 2022 Elsevier [28].

Figure 2

The schematic interpretation of the biosensor components [2]. The asterisk (*) represents only the full forms of the abbreviations (EIS, CV, DPV, Ref. index) & (SPR) & (MIP) listed inside the blocks (Recognition Signal, Transducer, and Recognition Element) respectively for Figure 2.

Figure 3

Additive Manufacturing Processes: (a) Vat photopolymerization (VP); (b) extrusion-based system (EBSs); (c) powder bed fusion (PBF); (d) material jetting (MJ); (e) binder jetting (BJ); (f) directed energy deposition (DED); (g) sheet lamination process (SLP) [96].

Figure 4

Images of 3D-printed nanocomposites for a wide range of applications, such as MEMS, photonics, microfluidics, biomedical devices, microelectronics, and telecommunication tools [94].

Figure 5

Images of 3D-printed electrocardiogram (ECG) biosensors: (a) 3D-printed sensing electrodes attached to skin © 2023 Elsevier Ltd. [121]; (b) DLP-printed conductive hydrogel © 2011 Elsevier Ltd. [126]; (c) 3D-printed dry electrode © 2022 Creative Commons-CC-BY 4.0. [122]; (d) MXene-based self-powered physiological sensing system © 2020 Creative Commons-CC-BY 4.0 [59]; (e) hydrogel–liquid metal composite © 2022 Elsevier Ltd. [127].

Figure 6

(a) Different electrode designs in 3 categories: flat circle, short-fingered, and long-fingered © 2022 Creative Commons CC-BY [136]; (b) 3D-printed EEG electrode coated with silver paint © 2016 MDPI [137]; (c) nine different 3D-printed electrode configurations © 2019 Velcescu et al. Creative Commons CC-BY [138]; (d) 3D-printed microneedle and flat electrode © 2020 Wiley-VCH GmbH [139]; (e) schematic of the hierarchical structure of a 3D-printed object and conductive network © 2019 Creative Commons CC-BY [140].

Figure 7

(a) Schematic view of proposed and fabricated 3D-printed rigid micro-bump-integrated liquid metal-based pressure sensor (3D-BLiPS) © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim [151]; (b) a 3D-printable highly conductive, flexible, stretchable one-part CNT–silicone ink © 2022 Wiley-VCH GmbH [152]; (c) a 3D-printed bioimpedance (Bio-Z) ring sensor for arterial blood flow and pressure sensing © 2023 Creative Commons CC BY 4.0 [148]; (d) The overview of Blood pressure predict wristband (BBPW): (A) The structure of BPPW and the materials used in each part. (B) The photograph of subjects wearing BPPW. (C) The photograph of BPPW; the whole length of BPPW is 26 cm © 2022 Creative Commons CC BY 4.0 [153]; (e) (a) Schematic illustrating the process of pulse pressure waveform (PPW) collection using the 3D-printed sensor. (b) Peak 1 and peak 2 represent systolic pressure and diastolic pressures, respectively. (c) PPW captured from a human subject. © 2023 Wiley-VCH GmbH [154].

Figure 8

(a) a. Scheme and b. photograph of the 3D-printed electrochemiluminescence enzyme biosensor device. c. Scheme of the 3D-printed dark box d. photograph of the analytical system during a measurement © 2023 Calabria et al., published by Elsevier B.V [167]; (b) 3D-printed workflow of glucose biosensor: a. bioprinter, b. printing of sensor ink onto plasma-treated Petri dish, c. UV curing, d. printed structure © 2023 Krstić et al., published by Elsevier Masson SAS [168]; (c) a 3D-printed biosensor for glucose sensing © 2018 Elsevier B.V. All rights reserved [162]; (d) a. Schematic visualization of the electrochemical sensor, showcasing, b. Final 3D-printed electrochemical sensor, where (1) is the carbon black/PLA electrode and (2) is the PLA sealing cap, c. Simultaneous monitoring of 5-HT overflow and circular contraction from the anorectum © 2020 Elsevier B.V. All rights reserved [169]; (e) 3D-printed poly(lactic acid) electrochemical multisensors © 2023 Escartín et al., published by Elsevier B.V. [170] (The chemically modified prototype, which acted as working electrode in the sensing process, was denoted PLA(#)* where # indicates the pressure of O₂ used during the process that transforms the electrochemically inert PLA into an electrochemically active material).

Figure 9

(a) Photometric biosensing module integrated with 3D-printed thermoplastic polyester case © 2022 Creative Commons Attribution CC BY 4.0 [181]; (b) 3D-printed toe-cuff sensor with PDMS using FRE technique © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [182]; (c) a wearable in-ear photoplethysmography sensor and a 3D-printed case to house the circuitry © Creative Commons Attribution CC BY 4.0 [179]; (d) schematic of the MXene-based self-powered physiological sensing system (MSP²S³), which comprises a MXene-based TENG (M-TENG) and a MXene-based pressure sensor (M-PS), both fabricated via additive manufacturing (3D printing) © 2022 Elsevier Ltd. All rights reserved [183]; (e) 3D-printed wearable pulse oximeter for the finger © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [182].

Figure 10

(a) Schematic of the fabrication process and the 3D-printed voltammetric sweat sensor (B) modified with a Fe(III) cluster © 2022 Creative Commons Attribution CC BY 4.0 [191]; (b) schematic illustration of an all-inclusive integrated wearable (AIIW) 3D-printed wearable bioelectronic patch: a. Top-view schematic showing the composition of the AIIW patch. b. Optical image of a flexible AIIW patch, c. The individual components of the AIIW patch, d. Cross-section of the AIIW patch, e. The individual components of the AIIW patch © 2021 Wiley-VCH GmbH [192]; (c) semisolid extrusion (SSE)-based 3D-printed e3-skin: A. Schematic of the SSE-based 3D printing, B. Schematic illustration of SSE printing procedures to prepare 2D and 3D architectures, C. 3D-printed e3-skin, D and E. Optical images of an e3-skin, F. Machine learning–powered multimodal e3-skin © 2023 Song et al. Creative Commons Attribution License 4.0 (CC BY) [194]; (d) 3D-printed electrochemical ring for sweat analysis © 2021 American Chemical Society [195]; (e) A. An exploded render highlights key components of the sweatainer system, B. The sweatainer mounted on the ventral forearm of an individual before the onset of sweat collection, C. The construct of the sweatainer eliminates uncontrolled fluid transport under mechanical loading, D. Illustration of the sweatainer highlighting key device, E. Renders of three-dimensional (3D) CBV designs, F. CAD render (top) and photograph of actual device (bottom), G. Photographic sequence highlighting the complete filling of a sweat collection reservoir. © 2022 Wu et al. Creative Commons Attribution License 4.0 (CC BY) [196].

Figure 11

(a) Fabrication steps of an all-printed triboelectric nanogenerator for tactile sensing © 2020 Elsevier Ltd. All rights reserved [203]; (b) Aerosol jet 3D-printed capacitive sensor: a. electrode length of 5 mm, b. electrode length of 1.5 mm, and c. high magnification image of the sensor in b © 2016 Elsevier B.V. All rights reserved [206]; (c) A self-powered triboelectric touch sensor made of 3D-printed materials © 2018 Elsevier Ltd. All rights reserved [201]; (d) 3D-printed mold-based graphite/PDMS sensor for tactile sensing: A. 3D printing resulted in the reusable mould, B. Then, graphite powder was cast, C. onto the mould, filling its trenches. This was followed by the casting of PDMS D, which was cured to form the sensor patches E. © 2018 Elsevier B.V. All rights reserved [204]; (e) Schematic of flexible wearable tactile sensors: a. Photograph and the schematic of the exploded view of the M2A3DNC pressure sensor for multiple physiological signals monitoring, b. A schematic representation of 3D printing of inks © 2021 Wiley-VCH GmbH [76].

Figure 12

(a) A schematic of 3D-printed electrode as a new platform for electrochemical immunosensor © 2020 Elsevier B.V. All rights reserved [213]; (b) 3D-printed electrochemical COVID-19 immunosensor, fabrication steps © 2021 Elsevier B.V. All rights reserved [214]; (c) 3D-printed sensor based on fiber Bragg grating (FBG) technology for respiratory rate (RR) and heart rate (HR) monitoring © 2022 Optica Publishing Group [211]; (d) a fast-response non-contact flexible humidity sensor: Top- direct write inkjet printing principle followed by liquid ajection and the optical images of different patterned structures, Bottom- Manufacturing process flow of the flexible humidity sensor © 2023 Chen et al. Creative Commons Attribution License 4.0 (CC BY) [215]; (e) a 3D-printed breath analyzer incorporating CeO2 nanoparticles © 2021 American Chemical Society [216].

Figure 13

Schematic of 3D-printed wearable biosensor challenges.

Figure 14

Schematic representing the prospects of the wearable biosensors © 2023 Commons Attribution License 4, © 2021 Wiley-VCH GmbH [227,228].