Easy-to-morph printable conductive Marangoni-driven 3D microdome geometries for fingertip-curved e-skin array with an ultragentle linear touch

Abstract

Continuously printable electronics have the significant advantage of being efficient for fabricating conductive polymer composites; however, the precise tailoring of the 3D hierarchical morphology of conductive nanocomposites in a simple dripping step remains challenging. Here, we introduce a one-step direct printing technique to construct diverse microdome morphologies influenced by the interfacial Marangoni effect and nanoparticle interactions. Using a jet dispenser for continuous processing, we effectively fabricated a soft epidermis-like e-skin containing 64 densely arrayed pressure sensing pixels with a hierarchical dome array for enhanced linearity and ultrasensitivity. The e-skin has 36 temperature-sensing pixels in the outer layer, with a shield-shaped dome that is insensitive to pressure stimuli. Our prosthetic finger inserted with the printed sensor arrays was capable of ultragentle detection and manipulation, such as stably holding a fragile biscuit, using a soft dropper to elaborately produce water droplets and harvesting soft fruits; these activities are challenging for existing high-sensitivity tactile sensors.

Keywords

e-skin / Marangoni flow / nanocomposite / printed electronics

References

[1] Wang S, Xu J, Wang W, et al. Skin electronics from scalable fabrication of an intrinsically stretchable transistor array. Nature. 2018; 555(7694): 83-88.

[2] Gong S, Zhang X, Nguyen XA, et al. Hierarchically resistive skins as specific and multimetric on-throat wearable biosensors. Nat Nanotechnol. 2023; 18(8): 889.

[3] Zhang B, Li J, Zhou J, et al. A three-dimensional liquid diode for soft, integrated permeable electronics. Nature. 2024; 628(8006): 84-92.

[4] Wang W, Jiang Y, Zhong D, et al. Neuromorphic sensorimotor loop embodied by monolithically integrated, low-voltage, soft e-skin. Science. 2023; 380(6646): 735-742.

[5] Boutry CM, Negre M, Jorda M, et al. A hierarchically patterned, bioinspired e-skin able to detect the direction of applied pressure for robotics. Sci Robot. 2018; 3(24): eaau6914.

[6] Jung D, Lim C, Shim HJ, et al. Highly conductive and elastic nanomembrane for skin electronics. Science. 2021; 373(6558): 1022-1026.

[7] Mannsfeld SC, Tee BC, Stoltenberg RM, et al. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nat Mater. 2010; 9(10): 859-864.

[8] Zhang L, Zhang ZW, Weisbecker H, et al. 3D morphable systems via deterministic microfolding for vibrational sensing, robotic implants, and reconfigurable telecommunication. Sci Adv. 2022; 8(51): eade0838.

[9] Zhai Y, De Boer A, Yan J, et al. Desktop fabrication of monolithic soft robotic devices with embedded fluidic control circuits. Sci Robot. 2023; 8(79): eadg3792.

[10] Heiden A, Preninger D, Lehner L, et al. 3D printing of resilient biogels for omnidirectional and exteroceptive soft actuators. Sci Robot. 2022; 7(63): eabk2119.

[11] Baek J, Shan YJ, Mylvaganan M, et al. Mold-free manufacturing of highly sensitive and fast-response pressure sensors through high-resolution 3D printing and conformal oxidative chemical vapor deposition polymers. Adv Mater. 2023; 35(41): e2304070a.

[12] Lee B, Cho H, Moon S, et al. Omnidirectional printing of elastic conductors for three-dimensional stretchable electronics. Nat Electron. 2023; 6(4): 307-318.

[13] Hui Y, Yao Y, Qian Q, et al. Three-dimensional printing of soft hydrogel electronics. Nat Electron. 2022; 5(12): 893-903.

[14] Lee WW, Tan YJ, Yao H, et al. A neuro-inspired artificial peripheral nervous system for scalable electronic skins. Sci Robot. 2019; 4(32): eaax2198.

[15] Kim Y, Chortos A, Xu W, et al. A bioinspired flexible organic artificial afferent nerve. Science. 2018; 360(6392): 998-1003.

[16] Zhong D, Wu C, Jiang Y, et al. High-speed and large-scale intrinsically stretchable integrated circuits. Nature. 2024; 627(8003): 313-320.

[17] Ershad F, Thukral A, Yue J, et al. Ultra-conformal drawn-on-skin electronics for multifunctional motion artifact-free sensing and point-of-care treatment. Nat Commun. 2020; 11(1): 3823.

[18] You I, Mackanic DG, Matsuhisa N, et al. Artificial multimodal receptors based on ion relaxation dynamics. Science. 2020; 370(6519): 961-965.

[19] Kim T, Kim J, You I, Oh J, Kim S-P, Jeong U. Dynamic tactility by position-encoded spike spectrum. Sci Robot. 2022; 7(63): eabl5761.

[20] Liu Z, Hu X, Bo R, et al. A three-dimensionally architected electronic skin mimicking human mechanosensation. Science. 2024; 384(6699): 987-994.

[21] Lee S, Byun SH, Kim CY, et al. Beyond human touch perception: an adaptive robotic skin based on gallium microgranules for pressure sensory augmentation. Adv Mater. 2022; 34(44): 2204805.

[22] Byun J, Lee Y, Yoon J, et al. Electronic skins for soft, compact, reversible assembly of wirelessly activated fully soft robots. Sci Robot. 2018; 3(18): eaas9020.

[23] Shi JL, Dai Y, Cheng Y, et al. Embedment of sensing elements for robust, highly sensitive, and cross-talk-free iontronic skins for robotics applications. Sci Adv. 2023; 9(9): eadf8831.

[24] Chun S, Kim JS, Yoo Y, et al. An artificial neural tactile sensing system. Nat Electron. 2021; 4(6): 429.

[25] Jiang Z, Chen N, Yi Z, et al. A 1.3-micrometre-thick elastic conductor for seamless on-skin and implantable sensors. Nat Electron. 2022; 5(11): 784-793.

[26] Lee S, Reuveny A, Reeder J, et al. A transparent bending-insensitive pressure sensor. Nat Nanotechnol. 2016; 11(5): 472.

[27] Lee S, Franklin S, Hassani FA, et al. Nanomesh pressure sensor for monitoring finger manipulation without sensory interference. Science. 2020; 370(6519): 966-970.

[28] Wang Y, Lee S, Yokota T, et al. A durable nanomesh on-skin strain gauge for natural skin motion monitoring with minimum mechanical constraints. Sci Adv. 2020; 6(33): eabb7043.

[29] Yokota T, Nakamura T, Kato H, et al. A conformable imager for biometric authentication and vital sign measurement. Nat Electron. 2020; 3(2): 113-121.

[30] Xiong Y, Wang Y, Zhang J, et al. Endowing TENGs with sequential logic. Device. 2024; 2(10): 100472.

[31] Lin X, Feng Z, Xiong Y, et al. Piezotronic neuromorphic devices: principle, manufacture, and applications. Intern J Extrem Manuf. 2024; 6(3): 032011.

[32] Ji J, Wang Z, Zhang F, et al. Pulse electrochemical synaptic transistor for supersensitive and ultrafast biosensors. InfoMat. 2023; 5(11): e12478.

[33] Lewis JA, Ahn BY. Three-dimensional printed electronics. Nature. 2015; 518(7537): 42-43.

[34] Song O, Rhee D, Kim J, et al. All inkjet-printed electronics based on electrochemically exfoliated two-dimensional metal, semiconductor, and dielectric. npj 2D Mater Appl. 2022; 6(1): 64.

[35] Yu Y, Li JH, Solomon SA, et al. All-printed soft human-machine interface for robotic physicochemical sensing. Sci Robot. 2022; 7(67): eabn0495.

[36] Qiu Y, Wang ZQ, Zhu PC, et al. A multisensory-feedback tactile glove with dense coverage of sensing arrays for object recognition. Chem Eng J. 2023; 455: 140890.

[37] Zhao JX, Lu HY, Zhang Y, et al. Direct coherent multi-ink printing of fabric supercapacitors. Sci Adv. 2021; 7(3): eabd6978.

[38] Kwon DA, Lee S, Kim CY, Kang I, Park S, Jeong JW. Body-temperature softening electronic ink for additive manufacturing of transformative bioelectronics via direct writing. Sci Adv. 2024; 10(9): eadn1186.

[39] Zhou T, Yuk H, Hu FQ, et al. 3D printable high-performance conducting polymer hydrogel for all-hydrogel bioelectronic interfaces. Nat Mater. 2023; 22(7): 895.

[40] Xie XJ, Xu ZG, Yu X, Jiang H, Li HJ, Feng WQ. Liquid-in-liquid printing of 3D and mechanically tunable conductive hydrogels. Nat Commun. 2023; 14(1): 4289.

[41] Yang CY, Stoeckel MA, Ruoko TP, et al. A high-conductivity n-type polymeric ink for printed electronics. Nat Commun. 2021; 12(1): 2354.

[42] Liu Y, Han F, Li FS, et al. Inkjet-printed unclonable quantum dot fluorescent anti-counterfeiting labels with artificial intelligence authentication. Nat Commun. 2019; 10(1): 2409.

[43] Lee W, Kim H, Kang I, et al. Universal assembly of liquid metal particles in polymers enables elastic printed circuit board. Science. 2022; 378(6620): 637-641.

[44] Veerapandian S, Jang W, Seol JB, et al. Hydrogen-doped viscoplastic liquid metal microparticles for stretchable printed metal lines. Nat Mater. 2021; 20(4): 533-540.

[45] Lee G-H, Lee DH, Jeon W, et al. Conductance stable and mechanically durable bi-layer EGaIn composite-coated stretchable fiber for 1D bioelectronics. Nat Commun. 2023; 14(1): 4173.

[46] Molina-Lopez F, Gao TZ, Kraft U, et al. Inkjet-printed stretchable and low voltage synaptic transistor array. Nat Commun. 2019; 10(1): 2676.

[47] Hu G, Yang L, Yang Z, et al. A general ink formulation of 2D crystals for wafer-scale inkjet printing. Sci Adv. 2020; 6(33): eaba5029.

[48] Kim F, Yang SE, Ju H, et al. Direct ink writing of three-dimensional thermoelectric microarchitectures. Nat Electron. 2021; 4(8): 579-587.

[49] Cao KL, Wu M, Bai JB, et al. Beyond skin pressure sensing: 3D printed laminated graphene pressure sensing material combines extremely low detection limits with wide detection range. Adv Funct Mater. 2022; 32(28): 2202360.

[50] Song Y, Tay RY, Li JH, et al. 3D-printed epifluidic electronic skin for machine learning-powered multimodal health surveillance. Sci Adv. 2023; 9(37): eadi6492.

[51] Chen X, Wang X, Chen PG, Liu QS. Thermal effects of substrate on Marangoni flow in droplet evaporation: response surface and sensitivity analysis. Int J Heat Mass Transfer. 2017; 113: 354-365.

[52] Zhang GN, Zhang HY, Yu R, Duan YQ, Huang YA, Yin ZP. Critical size/viscosity for coffee-ring-free printing of perovskite micro/nanopatterns. ACS Appl Mater Interfaces. 2022; 14(12): 14712-14720.

[53] Shen XY, Ho CM, Wong TS. Correction to “Minimal size of coffee ring structure”. J Phys Chem B. 2010; 114(16): 5269-5274.

[54] Beaton CF, Hewitt GF, Liley P. Physical property data for the design engineer. Hemisphere Publishing Corporation; 1989.

[55] Bae GY, Pak SW, Kim D, et al. Linearly and highly pressure-sensitive electronic skin based on a bioinspired hierarchical structural array. Adv Mater. 2016; 28(26): 5300-5306.

[56] Kim SW, Lee JH, Ko HJ, et al. Mechanically robust and linearly sensitive soft piezoresistive pressure sensor for a wearable human-robot interaction system. ACS Nano. 2024; 18(4): 3151-3160.

[57] Lee Y, Park J, Cho S, et al. Flexible ferroelectric sensors with ultrahigh pressure sensitivity and linear response over exceptionally broad pressure range. ACS Nano. 2018; 12(4): 4045-4054.

[58] Lee Y, Myoung J, Cho S, et al. Bioinspired gradient conductivity and stiffness for ultrasensitive electronic skins. ACS Nano. 2020; 15(1): 1795-1804.

[59] Zhang YF, Lu QC, He J, et al. Localizing strain via micro-cage structure for stretchable pressure sensor arrays with ultralow spatial crosstalk. Nat Commun. 2023; 14(1): 1252.

[60] Kim J, Park D, Moon S, et al. Omnidirectional tactile profiling using a deformable pressure sensor array based on localized piezoresistivity. Adv Mater Technol. 2022; 7(3): 2100688.

[61] Xiong WN, Zhang F, Qu SY, Yin LT, Li K, Huang YA. Marangoni-driven deterministic formation of softer, hollow microstructures for sensitivity-enhanced tactile system. Nat Commun. 2024; 15(1): 5596.

[62] Bai NN, Wang L, Wang Q, et al. Graded intrafillable architecture-based iontronic pressure sensor with ultra-broad-range high sensitivity. Nat Commun. 2020; 11(1): 209.

[63] Tian S, Wang Y, Deng H, Wang Y, Zhang X. Flexible pressure and temperature sensors towards e-skin: material, mechanism, structure and fabrication. Soft Sci. 2023; 3(3): 30.

[64] Su Q, Zou Q, Li Y, et al. A stretchable and strain-unperturbed pressure sensor for motion interference-free tactile monitoring on skins. Sci Adv. 2021; 7(48): eabi4563.

[65] Sliz R, Czajkowski J, Fabritius T. Taming the coffee ring effect: enhanced thermal control as a method for thin-film nanopatterning. Langmuir. 2020; 36(32): 9562-9570.

RIGHTS & PERMISSIONS

2025 The Author(s). InfoMat published by UESTC and John Wiley & Sons Australia, Ltd.