高灵敏度线性响应离电压力传感技术及其应用研究

皮肤是人体最大的感受器官，皮肤中的机械感受器能够将接触、振动等环境机械刺激转化为电信号，并传递到神经系统，赋予人类识别物体、辨别纹理等精细触觉感知能力。生物机械感受器激发了研究人员对于人工机械感受器（又称柔性压力传感器）的积极探索。柔性压力传感器可以将外界机械刺激转化为电信号，在构建智能机器人触觉、开发具有触觉感知功能的智能假肢、可穿戴医疗设备以及人机交互等领域具有广泛的应用前景。电容型柔性压力传感器结构简单，可以实现对静态力和动态力的响应，因此受到研究人员的广泛关注。但是其响应电容较小，容易受到环境中寄生电容和电磁噪音等的干扰。离电型压力传感器基于界面双电层效应，具有较大的单位面积电容，能够有效抑制环境中电磁噪音的干扰，实现超高的电容响应。本论文围绕离电型压力传感器，从双电层理论模型出发，通过传感机理分析、有限元仿真以及实验论证，系统研究了介电层离子动态约束、电极非平衡压缩以及材料压缩模量调谐三种提高离电压力传感器灵敏度的方法。传感器灵敏度不仅从32.70 kPa−1 成功提高至25,548.24 kPa−1，而且解决了过去高灵敏度和响应线性不兼容的问题，为其在人体生理信号监测、智能机器人手构建等领域的应用提供了有力支持。具体的创新工作如下：
（1）提出了一种离子动态约束传感机制，将离子液体和聚(偏氟乙烯-六氟丙烯) 混合纳米纤维嵌入热塑性聚氨酯基体中，制备得到以核-壳结构离子纳米纤维膜为介电层的离电压力传感器，可以实现应力触发下介电层界面离子的动态约束过程，为模仿生物机械感受器触觉感知过程提供了依据 。该传感器在0.04 Pa-209 kPa 的宽线性压力范围内具有32.70 kPa−1的高灵敏度以及0.035%的超高压力分辨率（预加载压力100 kPa），在生理信号监测、辅助物体识别等领域表现出潜在的应用价值。
（2）建立了一种弯曲引发的非平衡压缩策略，采用具有特殊分支瓣状的直立石墨烯电极，能够有效提高电极微结构的可压缩性，在离电型压力传感器双电层界面面积增长效率方面发挥了关键作用。克服了目前普遍使用的稳定轴向微结构策略（例如微金字塔）在压缩过程中容易出现的结构刚化、灵敏度和线性度不兼容的问题。该离电压力传感器在0.49 Pa-66.67 kPa 的宽压力范围内，实现了高灵敏度（185.09 kPa−1）和高线性度（R2=0.9999）的兼容。并且成功应用于机器人抓取任务中，借助多层感知（MLP）神经网络可以实现对不同材料、形状物体的识别。

（3）提出了一种基于压缩模量的传感器性能调制方法，不仅成功实现了离电压力传感器灵敏度的新突破，还可以根据应用场景的需求对传感器性能进行程式化定制。基于该理论制备的三维多孔石墨烯离电压力传感器展现出25,548.24 kPa−1的超高灵敏度，并且传感器的线性压力范围从15 kPa 到127 kPa 可调。在峰值压力为3.5 kPa 的1000 次加载、卸载循环中，传感器信号漂移小于0.5%。我们使用该传感器开发了一个压力反馈控制机器人手，可以自主调节抓取角度，精确跟踪气球内部的压力变化行为。

从离电型压力传感器的力学感知机理出发，我们设计得到了超高灵敏度、高分辨率的线性响应柔性压力传感器，为复杂场景下的触觉感知的应用开辟了新的机遇。

The skin is the largest sensory organ of the human body. Mechanical receptors within the skin can convert environmental mechanical stimuli such as touch and vibration into electrical signals, which are then transmitted to the nervous system, endowing humans
with the ability to recognize objects, discern textures, and perceive fine tactile sensations. The discovery of biological mechanoreceptors has spurred researchers to actively explore artificial mechanoreceptors, also known as flexible pressure sensors. Flexible pressure sensors have the capability to convert external mechanical stimuli into electrical signals, holding broad prospects for applications in fields such as constructing intelligent robotic touch systems, developing smart prosthetics with tactile sensing capabilities, wearable medical devices, and human-machine interaction. Capacitive flexible pressure sensors, characterized by their simple structure and ability to respond to both static and dynamic forces, have garnered significant attention from researchers. However, they tend to exhibit relatively small capacitance responses and are prone to interference from parasitic capacitance and electromagnetic noise present in the environment. Iontronic pressure sensors, based on the interface electrical double layer effect, possess larger unit-area capacitance, enabling them to effectively suppress interference from electromagnetic noise in the environment and achieve ultra-high capacitance response. This paper revolves around iontronic pressure sensors, through a systematic approach involving analysis of sensing mechanisms, finite element analysis, and experimental verification, three methods to enhance the sensitivity of iontronic pressure sensors are studied. These methods include dynamic ion confinement in the dielectric layer, electrode non-equilibrium compression, and material compressive modulus tuning The sensitivity of the sensor has been successfully increased from 32.70 kPa−1 to 25,548.24 kPa−1, addressing the previous issue of incompatibility between high sensitivity and response linearity. This provides robust support for its applications in fields such as monitoring physiological signals in the human body and constructing intelligent robotic hands.The specific innovative work is as follows:
(1) We propose a dynamic ion confinement sensing mechanism. By embedding a mixture of ionic liquid and poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers
into a thermoplastic polyurethane matrix, a core-shell structured ion nanofiber membrane has been prepared as the dielectric layer of an iontronic pressure sensor. This mechanism enables the dynamic confinement of ions at the interface of the dielectric layer under stress, providing a basis for mimicking the tactile perception process of biological mechanoreceptors.The sensor exhibits a high sensitivity of 32.70 kPa−1 within a wide linear pressure range from 0.04 Pa to 209 kPa, along with an ultra-high pressure resolution of 0.035% (preloading pressure 100 kPa). The sensor demonstrates potential application value in physiological signal monitoring, object recognition assistance, and other fields.

(2) Building upon the dynamic ion confinement within the dielectric layer, we pioneer a curvature-induced non-equilibrium compression strategy. Utilizing vertical graphene electrodes with distinctive branched morphology effectively enhances the compressibility of electrode, playing a crucial role in promoting the efficiency of interface
area growth at the electrical double layer of iontronic pressure sensors. This strategy overcomes the issues of structural stiffening, and incompatibility between sensitivity and linearity, commonly encountered with the prevailing stable axial microstructure strategy (such as micro-pyramids) during the compression process. This pressure sensor achieves high sensitivity (185.09 kPa−1) and excellent linearity (R2=0.9999) compatibility within a wide pressure range from 0.49 Pa to 66.67 kPa. It has been successfully applied in robotic grasping tasks, enabling the recognition of objects with different materials and shapes through Multilayer Perceptron (MLP) neural networks.

(3) We proposea method for modulating the performance of sensors based on compression modulus, which not only achieves a breakthrough in the sensitivity of iontronic pressure sensors but also allows for programmatically tailored sensor performance according to application requirements. Based on this theory, a three-dimensional porous graphene iontronic pressure sensor is fabricated, demonstrating an ultra-high sensitivity of 25,548.24 kPa−1 and an adjustable linear pressure range from 15 kPa to 127 kPa. In 1000 cycles of loading and unloading with a peak pressure of 3.5 kPa, the sensor's signal drift is less than 0.5%. We utilize this sensor to develop a pressure feedback-controlled robotic hand capable of autonomously adjusting grasping angles and accurately tracking pressure variations within balloons.

Starting from the mechanical perception mechanism of iontronic pressure sensors, we have designed ultra-high sensitivity, high-resolution linear response flexible pressure sensors, opening up new opportunities for tactile perception applications in complex scenarios.

[1] NGHIEM B T, SANDO I C, GILLESPIE R B, et al. Providing a sense of touch to prosthetic hands[J]. Plastic and Reconstructive Surgery, 2015, 135(6).
[2] CAMPERO M, BOSTOCK H. Unmyelinated afferents in human skin and their responsiveness to low temperature[J]. Neuroscience Letters, 2010, 470(3): 188-192.
[3] DAHIYA R S, METTA G, VALLE M, et al. Tactile sensing-from humans to humanoids[J]. IEEE Transactions on Robotics, 2010, 26(1): 1-20.
[4] KACZMAREK K, WEBSTER J, BACH-Y RITA P, et al. Electrotactile and vibrotactile displays for sensory substitution systems[J]. IEEE Transactions on Biomedical Engineering, 1991, 38 (1): 1-16.
[5] CAMPERO M, SERRA J, BOSTOCK H, et al. Slowly conducting afferents activated by innocuous low temperature in human skin[J]. The Journal of Physiology, 2001, 535(3): 855-865.
[6] JOHANSSON R S, VALLBO A B. Tactile sensibility in the human hand: relative and absolute densities of four types of mechanoreceptive units in glabrous skin[J]. The Journal of Physiology, 1979, 286(1): 283-300.
[7] CHORTOS A, LIU J, BAO Z. Pursuing prosthetic electronic skin[J]. Nature Materials, 2016, 15(9): 937-950.
[8] JOHANSSON R S, FLANAGAN J R. Coding and use of tactile signals from the fingertips in object manipulation tasks[J]. Nature Reviews Neuroscience, 2009, 10(5): 345-359.
[9] JOHANSSON R, LANDSTRO¨M U, LUNDSTRO¨M R. Responses of mechanoreceptive afferent units in the glabrous skin of the human hand to sinusoidal skin displacements[J]. Brain Research, 1982, 244(1): 17-25.
[10] LO¨FVENBERG J, JOHANSSON R. Regional differences and interindividual variability in sensitivity to vibration in the glabrous skin of the human hand[J]. Brain Research, 1984, 301 (1): 65-72.
[11] KNIBESTöL M. Stimulus-response functions of slowly adapting mechanoreceptors in the human glabrous skin area.[J]. The Journal of Physiology, 1975, 245(1): 63-80.
[12] LOEWENSTEIN W R, SKALAK R. Mechanical transmission in a Pacinian corpuscle. An analysis and a theory[J]. The Journal of Physiology, 1966, 182(2): 346-378.
[13] BRISBEN A J, HSIAO S S, JOHNSON K O. Detection of vibration transmitted through an object grasped in the hand[J]. Journal of Neurophysiology, 1999, 81(4): 1548-1558.
[14] ABRAIRA V E, GINTY D D. The sensory neurons of touch[J]. Neuron, 2013, 79(4): 618-639.
[15] JENMALM P, BIRZNIEKS I, GOODWIN A W, et al. Influence of object shape on responses of human tactile afferents under conditions characteristic of manipulation[J]. European Journal of Neuroscience, 2003, 18(1): 164-176.
[16] YU X, XIE Z, YU Y, et al. Skin-integrated wireless haptic interfaces for virtual and augmented reality[J]. Nature, 2019, 575(7783): 473-479.
[17] SUNDARAM S, KELLNHOFER P, LI Y, et al. Learning the signatures of the human grasp using a scalable tactile glove[J]. Nature, 2019, 569(7758): 698-702.
[18] ZHU M, SUN Z, CHEN T, et al. Low cost exoskeleton manipulator using bidirectional triboelectric sensors enhanced multiple degree of freedom sensory system[J]. Nature Communications, 2021, 12(1): 2692.
[19] OUYANG Q, WU J, SUN S, et al. Bio-inspired haptic feedback for artificial palpation in robotic surgery[J]. IEEE Transactions on Biomedical Engineering, 2021, 68(10): 3184-3193.
[20] ZHANG Z, ZHU Z, BAZOR B, et al. FeetBeat: A flexible iontronic sensing wearable detects pedal pulses and muscular activities[J]. IEEE Transactions on Biomedical Engineering, 2019, 66(11): 3072-3079.
[21] LIN Q, HUANG J, YANG J, et al. Highly sensitive flexible iontronic pressure sensor for fingertip pulse monitoring[J]. Advanced Healthcare Materials, 2020, 9(17): 2001023.
[22] PARK D Y, JOE D J, KIM D H, et al. Self-powered real-time arterial pulse monitoring using ultrathin epidermal piezoelectric sensors[J]. Advanced Materials, 2017, 29(37): 1702308.
[23] AMOLI V, KIM J S, KIM S Y, et al. Ionic tactile sensors for emerging human-interactive technologies: a review of recent progress[J]. Advanced Functional Materials, 2020, 30(20): 1904532.
[24] YANG J C, MUN J, KWON S Y, et al. Electronic skin: recent progress and future prospects for skin-attachable devices for health monitoring, robotics, and prosthetics[J]. Advanced Materials, 2019, 31(48): 1904765.
[25] 刘庆先. 基于复合多孔结构的离-电式柔性压力传感器[D]. 哈尔滨: 哈尔滨工业大学航天学院力学学科, 2022.
[26] QIN J, YIN L J, HAO Y N, et al. Flexible and stretchable capacitive sensors with different microstructures[J]. Advanced Materials, 2021, 33(34): 2008267.
[27] SHI J, DAI Y, CHENG Y, et al. Embedment of sensing elements for robust, highly sensitive, and cross-talk–free iontronic skins for robotics applications[J]. Science Advances, 9(9): eadf8831.
[28] CHANG H, KIM S, KANG T H, et al. Wearable piezoresistive sensors with ultrawide pressure range and circuit compatibility based on conductive-island-bridging nanonetworks[J]. ACS Applied Materials & Interfaces, 2019, 11(35): 32291-32300.
[29] ZHANG Y, XU S, FU H, et al. Buckling in serpentine microstructures and applications in elastomer-supported ultra-stretchable electronics with high areal coverage[J]. Soft Matter, 2013, 9: 8062-8070.
[30] XU S, ZHANG Y, JIA L, et al. Soft microfluidic assemblies of sensors, circuits, and radios for the skin[J]. Science, 2014, 344(6179): 70-74.
[31] LI R, SI Y, ZHU Z, et al. Supercapacitive iontronic nanofabric sensing[J]. Advanced Materials, 2017, 29(36): 1700253.
[32] LEE H, SHARMA R, PARK S, et al. Gradual electrical-double-layer modulation in ion-polymer networks for flexible pressure sensors with wide dynamic range[J]. Advanced Functional Materials, 2024, 34(7): 2302633.
[33] ZHU Z, LI R, PAN T. Imperceptible epidermal–iontronic interface for wearable sensing[J]. Advanced Materials, 2018, 30(6): 1705122.
[34] KIM K K, KIM M, PYUN K, et al. A substrate-less nanomesh receptor with meta-learning for rapid hand task recognition[J]. Nature Electronics, 2023, 6(1): 64-75.
[35] LU Y, WANG X, MAO S, et al. Smart batteries enabled by implanted flexible sensors[J]. Energy & Environmental Science, 2023, 16: 2448-2463.
[36] HUANG Y, ZHOU J, KE P, et al. A skin-integrated multimodal haptic interface for immersive tactile feedback[J]. Nature Electronics, 2023, 6(12): 1020-1031.
[37] HAN C, ZHANG H, CHEN Q, et al. A directional piezoelectric sensor based on anisotropic PVDF/MXene hybrid foam enabled by unidirectional freezing[J]. Chemical Engineering Journal, 2022, 450: 138280.
[38] ZHANG G, LIAO Q, MA M, et al. Uniformly assembled vanadium doped ZnO microflowers/ bacterial cellulose hybrid paper for flexible piezoelectric nanogenerators and self-powered sensors[J]. Nano Energy, 2018, 52: 501-509.
[39] ZHOU P, ZHENG Z, WANG B, et al. Self-powered flexible piezoelectric sensors based on selfassembled 10 nm BaTiO₃ nanocubes on glass fiber fabric[J]. Nano Energy, 2022, 99: 107400.
[40] MAHAPATRA S D, MOHAPATRA P C, ARIA A I, et al. Piezoelectric materials for energy harvesting and sensing applications: roadmap for future smart materials[J]. Advanced Science, 2021, 8(17): 2100864.
[41] YANG Z, ZHOU S, ZU J, et al. High-performance piezoelectric energy harvesters and their applications[J]. Joule, 2018, 2(4): 642-697.
[42] MENG K, XIAO X, WEI W, et al. Wearable pressure sensors for pulse wave monitoring[J]. Advanced Materials, 2022, 34(21): 2109357.
[43] HUANG J, LI D, ZHAO M, et al. Flexible electrically conductive biomass-based aerogels for piezoresistive pressure/strain sensors[J]. Chemical Engineering Journal, 2019, 373: 1357-1366.
[44] CHEN T, ZHANG X, HU X, et al. Sensitive piezoresistive sensors using ink-modified plant fiber sponges[J]. Chemical Engineering Journal, 2020, 401: 126029.
[45] AMOLI V, KIM J S, JEE E, et al. A bioinspired hydrogen bond-triggered ultrasensitive ionic mechanoreceptor skin[J]. Nature Communications, 2019, 10(1): 4019.
[46] CHEN Q, YANG J, CHEN B, et al. Wearable pressure sensors with capacitive response over a wide dynamic range[J]. ACS Applied Materials & Interfaces, 2022, 14(39): 44642-44651.
[47] SHI R, LOU Z, CHEN S, et al. Flexible and transparent capacitive pressure sensor with patterned microstructured composite rubber dielectric for wearable touch keyboard application[J]. Sci. China Mater, 2018, 61(12): 1587-1595.
[48] MANNSFELD S C B, TEE B C K, STOLTENBERG R M, et al. Highly sensitive flexiblepressure sensors with microstructured rubber dielectric layers[J]. Nature Materials, 2010, 9 (10): 859-864.
[49] CHENG W, WANG J, MA Z, et al. Flexible pressure sensor with high sensitivity and low hysteresis based on a hierarchically microstructured electrode[J]. IEEE Electron Device Letters, 2018, 39(2): 288-291.
[50] LEE H K, CHANG S I, YOON E. A flexible polymer tactile sensor: fabrication and modular expandability for large area deployment[J]. Journal of Microelectromechanical Systems, 2006, 15(6): 1681-1686.
[51] LEE H K, CHANG S I, YOON E. Dual-mode capacitive proximity sensor for robot application: implementation of tactile and proximity sensing capability on a single polymer platform using shared electrodes[J]. IEEE Sensors Journal, 2009, 9(12): 1748-1755.
[52] MAZZEO A D, KALB W B, CHAN L, et al. Paper-based, capacitive touch pads[J]. Advanced Materials, 2012, 24(21): 2850-2856.
[53] CHENG G, LIN Z H, DU Z L, et al. Simultaneously harvesting electrostatic and mechanical energies from flowing water by a hybridized triboelectric nanogenerator[J]. ACS Nano, 2014, 8(2): 1932-1939.
[54] YANG J, CHEN J, LIU Y, et al. Triboelectrification-based organic film nanogenerator for acoustic energy harvesting and self-powered active acoustic sensing[J]. ACS Nano, 2014, 8(3): 2649-2657.
[55] AL-KABBANY A M. Characteristics of a Kapton triboelectric nanogenerator-based touch button's voltage output[J]. Nano Energy, 2023, 114: 108620.
[56] QIAN J, HE J, QIAN S, et al. A nonmetallic stretchable nylon-modified high performance triboelectric nanogenerator for energy harvesting[J]. Advanced Functional Materials, 2020, 30 (4): 1907414.
[57] ARGYROPOULOU O D, PROTOGEROU A D, SFIKAKIS P P. Accelerated atheromatosis and arteriosclerosis in primary systemic vasculitides: current evidence and future perspectives [J]. Current Opinion in Rheumatology, 2018, 30(1): 36-43.
[58] WINDECKER S, BAX J J, MYAT A, et al. Future treatment strategies in ST-segment elevation myocardial infarction[J]. The Lancet, 2013, 382(9892): 644-657.
[59] OLIVER M F, OPIE L H. Management of acute myocardial infarction[J]. The Lancet, 2014, 383(9915): 409-410.
[60] ETTEHAD D, EMDIN C A, KIRAN A, et al. Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis[J]. The Lancet, 2016, 387(10022): 957-967.
[61] DENG C, TANG W, LIU L, et al. Self-powered insole plantar pressure mapping system[J]. Advanced Functional Materials, 2018, 28(29): 1801606.
[62] OXLEY T J, OPIE N L, JOHN S E, et al. Minimally invasive endovascular stent-electrode array for high-fidelity, chronic recordings of cortical neural activity[J]. Nature Biotechnology, 2016, 34(3): 320-327.
[63] DUKKIPATI S R, NEUZIL P, SKODA J, et al. Visual balloon-guided point-by-point ablation [J]. Circulation: Arrhythmia and Electrophysiology, 2010, 3(3): 266-273.
[64] HAN M, CHEN L, ARAS K, et al. Catheter-integrated soft multilayer electronic arrays for multiplexed sensing and actuation during cardiac surgery[J]. Nature Biomedical Engineering, 2020, 4(10): 997-1009.
[65] KIM J, LEE M, SHIM H J, et al. Stretchable silicon nanoribbon electronics for skin prosthesis [J]. Nature communications, 2014, 5(1): 5747.
[66] CHANG Y, WANG L, LI R, et al. First decade of interfacial iontronic sensing: from droplet sensors to artificial skins[J]. Advanced Materials, 2021, 33(7): 2003464.
[67] JI B, ZHOU Q, HU B, et al. Bio-inspired hybrid dielectric for capacitive and triboelectric tactile sensors with high sensitivity and ultrawide linearity range[J]. Advanced Materials, 2021, 33 (27): 2100859.
[68] HA K H, ZHANG W, JANG H, et al. Highly sensitive capacitive pressure sensors over a wide pressure range enabled by the hybrid responses of a highly porous nanocomposite[J]. Advanced Materials, 2021, 33(48): 2103320.
[69] WAN Y, QIU Z, HONG Y, et al. A highly sensitive flexible capacitive tactile sensor with sparse and high-aspect-ratio microstructures[J]. Advanced Electronic Materials, 2018, 4(4): 1700586.
[70] LEE S, FRANKLIN S, HASSANI F A, et al. Nanomesh pressure sensor for monitoring finger manipulation without sensory interference[J]. Science, 2020, 370(6519): 966-970.
[71] PRUVOST M, SMIT W J, MONTEUX C, et al. Polymeric foams for flexible and highly sensitive low-pressure capacitive sensors[J]. npj Flexible Electronics, 2019, 3(1): 7.
[72] WAN S, BI H, ZHOU Y, et al. Graphene oxide as high-performance dielectric materials for capacitive pressure sensors[J]. Carbon, 2017, 114: 209-216.
[73] YANG J, TANG D, AO J, et al. Ultrasoft liquid metal elastomer foams with positive and negative piezopermittivity for tactile sensing[J]. Advanced Functional Materials, 2020, 30(36): 2002611.
[74] CHHETRY A, SHARMA S, YOON H, et al. Enhanced sensitivity of capacitive pressure and strain sensor based on CaCu3Ti4O12 wrapped hybrid sponge for wearable applications[J]. Advanced Functional Materials, 2020, 30(31): 1910020.
[75] NIE B, XING S, BRANDT J D, et al. Droplet-based interfacial capacitive sensing[J]. Lab on a Chip, 2012, 12(6): 1110-1118.
[76] OLDHAM K B. A Gouy–Chapman–Stern model of the double layer at a (metal)/(ionic liquid) interface[J]. Journal of Electroanalytical Chemistry, 2008, 613(2): 131-138.
[77] ZHAO C, WANG Y, TANG G, et al. Ionic flexible sensors: mechanisms, materials, structures, and applications[J]. Advanced Functional Materials, 2022, 32(17): 2110417.
[78] NIE B, LI R, BRANDT J D, et al. Iontronic microdroplet array for flexible ultrasensitive tactile sensing[J]. Lab on a Chip, 2014, 14(6): 1107-1116.
[79] YANG X, WANG Y, QING X. A flexible capacitive pressure sensor based on ionic liquid[J]. Sensors, 2018, 18(7).
[80] QIU Z, WAN Y, ZHOU W, et al. Ionic skin with biomimetic dielectric layer templated from Calathea Zebrine leaf[J]. Advanced Functional Materials, 2018, 28(37): 1802343.
[81] WANG Q, LI Y, XU Q, et al. Finger–coding intelligent human–machine interaction system based on all–fabric ionic capacitive pressure sensors[J]. Nano Energy, 2023, 116: 108783.
[82] JIN M L, PARK S, LEE Y, et al. An ultrasensitive, visco-poroelastic artificial mechanotransducer skin inspired by Piezo2 protein in mammalian Merkel cells[J]. Advanced Materials, 2017, 29(13): 1605973.
[83] CHO S H, LEE S W, YU S, et al. Micropatterned pyramidal ionic gels for sensing broad-range pressures with high sensitivity[J]. ACS Applied Materials & Interfaces, 2017, 9(11): 10128-10135.
[84] SU Q, HUANG X, LAN K, et al. Highly sensitive ionic pressure sensor based on concave meniscus for electronic skin[J]. Journal of Micromechanics and Microengineering, 2020, 30 (1): 015009.
[85] CHHETRY A, KIM J, YOON H, et al. Ultrasensitive interfacial capacitive pressure sensor based on a randomly distributed microstructured iontronic film for wearable applications[J]. ACS Applied Materials & Interfaces, 2019, 11(3): 3438-3449.
[86] BAI N, WANG L, WANG Q, et al. Graded intrafillable architecture-based iontronic pressure sensor with ultra-broad-range high sensitivity[J]. Nature Communications, 2020, 11(1): 209.
[87] MARSHALL K, PATAPOUTIAN A. Getting a grip on touch receptors[J]. Science, 2020, 368 (6497): 1311-1312.
[88] ZIMMERMAN A, BAI L, GINTY D D. The gentle touch receptors of mammalian skin[J]. Science, 2014, 346(6212): 950-954.
[89] HANDLER A, GINTY D D. The mechanosensory neurons of touch and their mechanisms of activation[J]. Nature Reviews Neuroscience, 2021, 22(9): 521-537.
[90] NEUBARTH N L, EMANUEL A J, LIU Y, et al. Meissner corpuscles and their spatially intermingled afferents underlie gentle touch perception[J]. Science, 2020, 368(6497): eabb2751.
[91] MARICICH S M, WELLNITZ S A, NELSON A M, et al. Merkel cells are essential for lighttouch responses[J]. Science, 2009, 324(5934): 1580-1582.
[92] WOO S H, RANADE S, WEYER A D, et al. Piezo2 is required for Merkel-cell mechanotransduction[J]. Nature, 2014, 509(7502): 622-626.
[93] SCHRENK-SIEMENS K, WENDE H, PRATO V, et al. PIEZO2 is required for mechanotransduction in human stem cell–derived touch receptors[J]. Nature neuroscience, 2015, 18(1): 10-16.
[94] CHUNG H U, KIM B H, LEE J Y, et al. Binodal, wireless epidermal electronic systems with in-sensor analytics for neonatal intensive care[J]. Science, 2019, 363(6430): eaau0780.
[95] BOUTRY C M, KAIZAWA Y, SCHROEDER B C, et al. A stretchable and biodegradable strain and pressure sensor for orthopaedic application[J]. Nature Electronics, 2018, 1(5): 314-321.
[96] LIU Z, WANG G, YE C, et al. An ultrasensitive contact lens sensor based on self-assembly graphene for continuous intraocular pressure monitoring[J]. Advanced Functional Materials, 2021, 31(29): 2010991.
[97] OUYANG Q, WU J, SUN S, et al. Bio-inspired haptic feedback for artificial palpation in robotic surgery[J]. IEEE Transactions on Biomedical Engineering, 2021, 68(10): 3184-3193.
[98] LI F, WANG R, SONG C, et al. A skin-inspired artificial mechanoreceptor for tactile enhancement and integration[J]. ACS Nano, 2021, 15(10): 16422-16431.
[99] CHUN S, KIM J S, YOO Y, et al. An artificial neural tactile sensing system[J]. Nature Electronics, 2021, 4(6): 429-438.
[100] GU G, ZHANG N, XU H, et al. A soft neuroprosthetic hand providing simultaneous myoelectric control and tactile feedback[J]. Nature Biomedical Engineering, 2023, 7(4): 589-598.
[101] KIM J S, LEE S C, HWANG J, et al. Enhanced sensitivity of iontronic graphene tactile sensors facilitated by spreading of ionic liquid pinned on graphene grid[J]. Advanced Functional Materials, 2020, 30(14): 1908993.
[102] LIU Q, LIU Z, LI C, et al. Highly transparent and flexible iontronic pressure sensors based on an opaque to transparent transition[J]. Advanced Science, 2020, 7(10): 2000348.
[103] LI R, SI Y, ZHU Z, et al. Supercapacitive iontronic nanofabric sensing[J]. Advanced Materials, 2017, 29(36): 1700253.
[104] SHEN Z, ZHU X, MAJIDI C, et al. Cutaneous ionogel mechanoreceptors for soft machines, physiological sensing, and amputee prostheses[J]. Advanced Materials, 2021, 33(38): 2102069.
[105] SHARMA S, CHHETRY A, ZHANG S, et al. Hydrogen-bond-triggered hybrid nanofibrous membrane-based wearable pressure sensor with ultrahigh sensitivity over a broad pressure range [J]. ACS Nano, 2021, 15(3): 4380-4393.
[106] LUO Y, CHEN X, TIAN H, et al. Gecko-inspired slant hierarchical microstructure-based ultrasensitive iontronic pressure sensor for intelligent interaction[J]. Research, 2022.
[107] JI B, ZHOU Q, HU B, et al. Bio-inspired hybrid dielectric for capacitive and triboelectric tactile sensors with high sensitivity and ultrawide linearity range[J]. Advanced Materials, 2021, 33 (27): 2100859.
[108] CAO Y, MORRISSEY T G, ACOME E, et al. A transparent, self-healing, highly stretchable ionic conductor[J]. Advanced Materials, 2017, 29(10): 1605099.
[109] CAO Y, TAN Y J, LI S, et al. Self-healing electronic skins for aquatic environments[J]. Nature Electronics, 2019, 2(2): 75-82.
[110] NAYERI M, ARONSON M T, BERNIN D, et al. Surface effects on the structure and mobility of the ionic liquid C6C1ImTFSI in silica gels[J]. Soft Matter, 2014, 10(30): 5618-5627.
[111] DHUMAL N R, NOACK K, KIEFER J, et al. Molecular structure and interactions in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[J]. The Journal of Physical Chemistry A, 2014, 118(13): 2547-2557.
[112] RAMESH S, LIEW C W. Dielectric and FTIR studies on blending of [xPMMA–(1−x)PVC] with LiTFSI[J]. Measurement, 2013, 46(5): 1650-1656.
[113] CHEN C, YING W B, LI J, et al. A self-healing and ionic liquid affiliative polyurethane toward a Piezo 2 protein inspired ionic skin[J]. Advanced Functional Materials, 2022, 32(4): 2106341.
[114] NIE B, LI R, CAO J, et al. Flexible transparent iontronic film for interfacial capacitive pressure sensing[J]. Advanced Materials, 2015, 27(39): 6055-6062.
[115] YIN M J, YIN Z, ZHANG Y, et al. Micropatterned elastic ionic polyacrylamide hydrogel for low-voltage capacitive and organic thin-film transistor pressure sensors[J]. Nano Energy, 2019, 58: 96-104.
[116] PANG X D, TAN H Z, DURLACH N I. Manual discrimination of force using active finger motion[J]. Perception & psychophysics, 1991, 49(6): 531-540.
[117] WANG J, SUZUKI R, SHAO M, et al. Capacitive pressure sensor with wide-range, bendable, and high sensitivity based on the bionic Komochi Konbu structure and Cu/Ni nanofiber network [J]. ACS Applied Materials & Interfaces, 2019, 11(12): 11928-11935.
[118] TAY R Y, LI H, LIN J, et al. Lightweight, superelastic boron nitride/polydimethylsiloxane foam as air dielectric substitute for multifunctional capacitive sensor applications[J]. Advanced Functional Materials, 30(10): 1909604.
[119] KWON D, LEE T I, SHIM J, et al. Highly sensitive, flexible, and wearable pressure sensor based on a giant piezocapacitive effect of three-dimensional microporous elastomeric dielectric layer[J]. ACS Applied Materials & Interfaces, 2016, 8(26): 16922-16931.
[120] XIONG Y, SHEN Y, TIAN L, et al. A flexible, ultra-highly sensitive and stable capacitive pressure sensor with convex microarrays for motion and health monitoring[J]. Nano Energy, 2020, 70: 104436.
[121] CHHETRY A, SHARMA S, YOON H, et al. Enhanced sensitivity of capacitive pressure and strain sensor based on CaCu3Ti4O12 wrapped hybrid sponge for wearable applications[J]. Advanced Functional Materials, 2020, 30(31): 1910020.
[122] CHOI J, KWON D, KIM K, et al. Synergetic effect of porous elastomer and percolation of carbon nanotube filler toward high performance capacitive pressure sensors[J]. ACS Applied Materials & Interfaces, 2020, 12(1): 1698-1706.
[123] LUO Y, SHAO J, CHEN S, et al. Flexible capacitive pressure sensor enhanced by tilted micropillar arrays[J]. ACS Applied Materials & Interfaces, 2019, 11(19): 17796-17803.
[124] ZHOU H, WANG M, JIN X, et al. Capacitive pressure sensors containing reliefs on solutionprocessable hydrogel electrodes[J]. ACS Applied Materials & Interfaces, 2021, 13(1): 1441-1451.
[125] QIU J, GUO X, CHU R, et al. Rapid-response, low detection limit, and high-sensitivity capacitive flexible tactile sensor based on three-dimensional porous dielectric layer for wearable electronic skin[J]. ACS Applied Materials & Interfaces, 2019, 11(43): 40716-40725.
[126] JIN T, PAN Y, JEON G J, et al. Ultrathin nanofibrous membranes containing insulating microbeads for highly sensitive flexible pressure sensors[J]. ACS Applied Materials & Interfaces, 2020, 12(11): 13348-13359.
[127] PARK J, LEE Y, HONG J, et al. Giant tunneling piezoresistance of composite elastomers with interlocked microdome arrays for ultrasensitive and multimodal electronic skins[J]. ACS Nano, 2014, 8(5): 4689-4697.
[128] WANG X, GU Y, XIONG Z, et al. Silk-molded flexible, ultrasensitive, and highly stable electronic skin for monitoring human physiological signals[J]. Advanced Materials, 2014, 26(9):1336-1342.
[129] SUNDARAM S, KELLNHOFER P, LI Y, et al. Learning the signatures of the human grasp using a scalable tactile glove[J]. Nature, 2019, 569(7758): 698-702.
[130] LI G, LIU S, WANG L, et al. Skin-inspired quadruple tactile sensors integrated on a robot hand enable object recognition[J]. Science Robotics, 2020, 5(49): eabc8134.
[131] MANNSFELD S C B, TEE B C K, STOLTENBERG R M, et al. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers[J]. Nature Materials, 2010, 9 (10): 859-864.
[132] LIPOMI D J, VOSGUERITCHIAN M, TEE B C K, et al. Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes[J]. Nature Nanotechnology, 2011, 6(12):788-792.
[133] SU Q, ZOU Q, LI Y, et al. A stretchable and strain-unperturbed pressure sensor for motion interference–free tactile monitoring on skins[J]. Science Advances, 7(48): eabi4563.
[134] TAO K, CHEN Z, YU J, et al. Ultra-sensitive, deformable, and transparent triboelectric tactile sensor based on micro-pyramid patterned ionic hydrogel for interactive human–machine interfaces[J]. Advanced Science, 2022, 9(10): 2104168.
[135] ZHU P, DU H, HOU X, et al. Skin-electrode iontronic interface for mechanosensing[J]. Nature Communications, 2021, 12(1): 4731.
[136] KUDIN K N, SCUSERIA G E, YAKOBSON B I. C2F, BN, AND C nanoshell elasticity from ab initio computations[J]. Physical Review B, 2001, 64: 0-0.
[137] SUN J, RATTANASAWATESUN T, TANG P, et al. Insights into the mechanism for vertical graphene growth by plasma-enhanced chemical vapor deposition[J]. ACS Applied Materials & Interfaces, 2022, 14(5): 7152-7160.
[138] WU, YANG. Effects of localized electric field on the growth of carbon nanowalls[J]. Nano Letters, 2002, 2(4): 355-359.
[139] ZHAO J, SHAYGAN M, ECKERT J, et al. A growth mechanism for free-standing vertical graphene[J]. Nano Letters, 2014, 14(6): 3064-3071.
[140] ZHAO J, GUO H, LIU H, et al. Carbon nanotube network topology-enhanced iontronic capacitive pressure sensor with high linearity and ultrahigh sensitivity[J]. ACS Applied Materials & Interfaces, 2023, 15(40): 47327-47337.
[141] SEO D H, PINEDA S, YICK S, et al. Plasma-enabled sustainable elemental lifecycles: honeycomb-derived graphenes for next-generation biosensors and supercapacitors[J]. Green Chemistry, 2015, 17(4): 2164-2171.
[142] NIYOGI S, BEKYAROVA E, ITKIS M E, et al. Spectroscopy of covalently functionalized graphene[J]. Nano Letters, 2010, 10(10): 4061-4066.
[143] HUANG Z, KONG D, ZHANG Y, et al. Vertical graphenes grown on a flexible graphite paper as an all-carbon current collector towards stable Li deposition[J]. Research, 2020.
[144] HAN Z J, PINEDA S, MURDOCK A T, et al. RuO2-coated vertical graphene hybrid electrodes for high-performance solid-state supercapacitors[J]. Journal of Materials Chemistry A, 2017, 5 (33): 17293-17301.
[145] ZHENG W, ZHAO X, FU W. Review of vertical graphene and its applications[J]. ACS Applied Materials & Interfaces, 2021, 13(8): 9561-9579.
[146] DENG C, GAO P, LAN L, et al. Ultrasensitive and highly stretchable multifunctional strain sensors with timbre-recognition ability based on vertical graphene[J]. Advanced Functional Materials, 2019, 29(51): 1907151.
[147] BAI N, WANG L, XUE Y, et al. Graded interlocks for iontronic pressure sensors with high sensitivity and high linearity over a broad range[J]. ACS Nano, 2022, 16(3): 4338-4347.
[148] YANG J, LI Z, ZHANG X, et al. Merkel cell-like artificial mechanoreceptor with high sensitivity and high resolution over a wide linear range[J]. Cell Reports Physical Science, 2022, 3 (10): 101101.
[149] ZHAO Y, YANG N, CHU X, et al. Wide-humidity range applicable, anti-freezing, and healable zwitterionic hydrogels for ion-leakage-free iontronic sensors[J]. Advanced Materials, 2023, 35 (22): 2211617.
[150] LU P, WANG L, ZHU P, et al. Iontronic pressure sensor with high sensitivity and linear response over a wide pressure range based on soft micropillared electrodes[J]. Science Bulletin, 2021, 66(11): 1091-1100.
[151] YOU I, MACKANIC D G, MATSUHISA N, et al. Artificial multimodal receptors based on ion relaxation dynamics[J]. Science, 2020, 370(6519): 961-965.
[152] DELMAS P, HAO J, RODAT-DESPOIX L. Molecular mechanisms of mechanotransduction in mammalian sensory neurons[J]. Nature Reviews Neuroscience, 2011, 12(3): 139-153.
[153] ZHANG Y, LU Q, HE J, et al. Localizing strain via micro-cage structure for stretchable pressure sensor arrays with ultralow spatial crosstalk[J]. Nature Communications, 2023, 14(1): 1252.
[154] QIAO H, SUN S, WU P. Non-equilibrium-growing aesthetic ionic skin for fingertip-like strainundisturbed tactile sensation and texture recognition[J]. Advanced Materials, 2023, 35(21): 2300593.
[155] LUO Y, ABIDIAN M R, AHN J H, et al. Technology roadmap for flexible sensors[J]. ACS Nano, 2023, 17(6): 5211-5295.
[156] BAI N, WANG L, XUE Y, et al. Graded interlocks for iontronic pressure sensors with high sensitivity and high linearity over a broad range[J]. ACS Nano, 2022, 16(3): 4338-4347.
[157] YANG R, DUTTA A, LI B, et al. Iontronic pressure sensor with high sensitivity over ultra-broad linear range enabled by laser-induced gradient micro-pyramids[J]. Nature Communications, 2023, 14(1): 2907.
[158] YUAN Y M, LIU B, ADIBEIG M R, et al. Microstructured polyelectrolyte elastomer-based ionotronic sensors with high sensitivities and excellent stability for artificial skins[J]. Advanced Materials, 2023, 36(11): 2310429.
[159] YUE Q, XIAO S, LI Z, et al. Ultra-sensitive pressure sensors based on large alveolar deep tooth electrode structures with greatly stretchable oriented fiber membrane[J]. Chemical Engineering Journal, 2022, 443: 136370.
[160] BAI N, XUE Y, CHEN S, et al. A robotic sensory system with high spatiotemporal resolution for texture recognition[J]. Nature Communications, 2023, 14(1): 7121.
[161] LI L, ZHU G, WANG J, et al. A flexible and ultrasensitive interfacial iontronic multisensory sensor with an array of unique “cup-shaped”microcolumns for detecting pressure and temperature[J]. Nano Energy, 2023, 105: 108012.
[162] BAI N, WANG L, WANG Q, et al. Graded intrafillable architecture-based iontronic pressure sensor with ultra-broad-range high sensitivity[J]. Nature Communications, 2020, 11(1): 209.
[163] PERSSON B N J. Contact mechanics for randomly rough surfaces[J]. Surface Science Reports, 2006, 61(4): 201-227.
[164] XU L, GAO S, GUO Q, et al. A solvent-exchange strategy to regulate noncovalent interactions for strong and antiswelling hydrogels[J]. Advanced Materials, 2020, 32(52): 2004579.
[165] WANG Q, LI Y, XU Q, et al. Finger–coding intelligent human–machine interaction system based on all–fabric ionic capacitive pressure sensors[J]. Nano Energy, 2023, 116: 108783.
[166] MENG K, XIAO X, LIU Z, et al. Kirigami-inspired pressure sensors for wearable dynamic cardiovascular monitoring[J]. Advanced Materials, 2022, 34(36): 2202478.
[167] HE J, XIAO P, LU W, et al. A universal high accuracy wearable pulse monitoring system via high sensitivity and large linearity graphene pressure sensor[J]. Nano Energy, 2019, 59: 422-433.