FULL PAPER www.afm-journal.de © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1807343 (1 of 11) Paper has been utilized as an ideal platform for chemical, biological, and mechanical sensing for its fibrous structures and properties in addition to its low cost. However, current studies on pressure-sensitive papers have not fully utilized the unique advantages of papers, such as printability, cuttability, and foldability. Moreover, the existing resistive, capacitive, and triboelectric sensing modalities have long-standing challenges in sensitivity, noise- proofing, response time, linearity, etc. Here, a novel flexible iontronic sensing mechanism, referred to as iontronic sensing paper (ISP), is introduced to the classic paper substrates by incorporating both ionic and conductive patterns into an all-in-one flexible sensing platform. The ISP can then be structured into 2D or 3D tactile-sensitive origamis only by the paper-specific manipulations of printing, cutting, folding, and gluing. Notably, the ISP device possesses a device sensitivity of 10 nF kPa -1 cm -2 , which is thousands of times higher than that of the commercial counterpart, a resolution of 6.25 Pa, a single-millisecond response time, and a high linearity (R 2 > 0.996). Benefiting from the unique properties of the fibrous paper structures and its remarkable performances, the ISP devices hold enormous potential for the emerging human–machine interfaces, including smart packaging, health wearables, and pressure-sensitive paper matrix. disposable, degradable material at a low cost, paper has long been utilized as a flex- ible platform for chemical and biological sensing. For instance, the pH papers, blood glucose-sensing strips, and early pregnancy detection kits are the most notable ones, along with the recent devel- opments of organic gas sensors, DNA and protein sensors, and heavy ion detection devices. [1–15] Furthermore, benefiting from their fibrous structure, papers can be modified with functional additives, such as carbon-derived materials (e.g., carbon nanotube (CNT) and graphene), conduc- tive polymers, and metallic nanocompos- ites, leading to new functionalities and sensing modalities. [16–21] Among these emerging functional papers, pressure- sensitive papers can be configured with a simple device architecture due to its straightforward sensing principles. [22–25] Although recent studies have successfully exhibited the device flexibility, low-cost manufacturability, and disposability, the additional unique natural advantages of paper have not been fully utilized, such as printability, cutta- bility, and foldability. The previously reported pressure-sensitive papers, along with the pressure sensors made of them are primarily based on three existing sensing mechanisms, i.e., resistive, capacitive, and triboelectric. [22,26,27] The resistive pressure-sensing papers detect the variations of the electrical resistance induced by the change of the contact area between two resistor structures upon the applied pressure, which can be prepared by dip coating and spray coating of a particular conductive material. Ren’s group has reported a novel graphene paper prepared by immersing tissue papers into a graphene oxide solution, and consecutively, this paper pressure sensing device has exhibited a sensitivity of 17.2 kPa -1 within the range of 2 kPa. [22] Cheng’s group has published a gold nanowire coated paper as a functional sensing material, the prepared pressure sensing device shows a device sensitivity of 1.14 kPa -1 within the range of 5 kPa. [25] However, the nonlinearity between the resistance measurements and the pressure readings can lead to substantial reduction in the device sensitivity as pressure increases. For instance, the sensitivity of the graphene-paper pressure sensor dramatically declines from 17.2 to 0.012 kPa -1 beyond its range limit of 2 kPa, thus restricting its practical utilities and applications. [22] Alternatively, the capacitive pressure-sensitive papers typically utilize parallel electrodes sandwiching a compressible dielectric layer. [28–30] As the loading pressure increases, the distance between two parallel All-in-One Iontronic Sensing Paper Sen Li, Ning Pan, Zijie Zhu, Ruya Li, Baoqing Li, Jiaru Chu, Guanglin Li, Yu Chang,* and Tingrui Pan* DOI: 10.1002/adfm.201807343 S. Li, Prof. G. Li, Dr. Y. Chang Bionic Sensing and Intelligence Center (BSIC) Institute of Biomedical and Health Engineering Shenzhen Institutes of Advanced Technology Chinese Academy of Science 1068 Xueyuan Avenue, Shenzhen 518055, China E-mail: yu.chang@siat.ac.cn S. Li, Prof. B. Li, Prof. J. Chu Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China 96 Jinzhai Road, Hefei 230027, China Prof. N. Pan, Dr. Z. Zhu, Prof. R. Li, Dr. Y. Chang, Prof. T. Pan Micro-Nano Innovations (MINI) Laboratory Department of Biomedical Engineering University of California Davis, One Shields Avenue, Davis, CA 95616, USA E-mail: trpan@ucdavis.edu The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201807343. Paper Electronics 1. Introduction Paper, made of natural or artificial cellulose fibers with additives, has evolved throughout human history and played a very important role in our daily life, primarily to record and spread information. Being a soft, foldable, printable, cuttable, Adv. Funct. Mater. 2019, 1807343