Contents lists available at ScienceDirect Nano Energy journal homepage: www.elsevier.com/locate/nanoen Full paper Highly stretchable integrated system for micro-supercapacitor with AC line filtering and UV detector Chen Chen a , Jun Cao a , Xinyu Wang a , Qiongqiong Lu a , Mingming Han a , Qingrong Wang a , Haitao Dai b , Zhiqiang Niu a, ⁎ , Jun Chen a,d , Sishen Xie c a Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin 300071, PR China b Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072, PR China c Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, PR China d Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, PR China ARTICLE INFO Keywords: Micro-supercapacitors Carbon nanotube Stretchable AC line filtering UV detection ABSTRACT In-plane micro-supercapacitors (MSCs) possess higher volumetric energy density and are thus more compact compared with traditional aluminum electrolytic capacitors (AECs). As a result, developing in-plane MSCs with AC line filtering function is desired to replace the AECs and integrate with other electronic devices. Here, highly stretchable integrated system for in-plane MSCs with AC line filtering and UV detector were fabricated by de- signing buckled micro-electrodes based on SWCNT film and TiO 2 NPs. Although gel electrolyte was used in these MSCs, they still show an ultrafast frequency response with a phase angle of -75.2° because of their unique structure. Such MSCs thus can function as the AC line filtering devices. Furthermore, their AC line filtering behavior remains almost unchanged even stretched up to 200%. Further coating TiO 2 NPs on the buckled SWCNT micro-electrodes is able to endow the MSCs with another ability of UV photodetection with the sensi- tivity of 6.2. Importantly, such integrated device can still show stable photocurrent response and capacitance behaviors at different stretching times and even repeated stretching 100 times. The rational design of such stretchable integrated system for MSCs with AC line filtering and UV photodetector will pave the way for the applications in assembling supercapacitors and other electronics into highly stretchable integrated devices. 1. Introduction Aluminum electrolytic capacitor (AEC) is commonly used for AC line filtering and often one of the bulkiest components in most line- powered electronic systems. Owing to the large volume and heavy component of traditional AECs, their applications in some portable electronics are hindered [1–4]. Compared with AECs, in-plane micro- supercapacitors (MSCs) that is a novel class of micro-scale power sources with electrodes in a micro-scale level possess higher volumetric energy density [3,5–12]. The opened side edges and smaller sizes of the MSC electrodes effectively shorten the diffusion path of ions and are greatly significant to enhance the ability of the electrolyte ions to in- filtrate into the micro-electrodes, enhancing the frequency response of MSCs [9,13–18]. Therefore, some MSCs could efficiently filter a 120 Hz ripple (60 Hz, the United States standard) [2,3]. Furthermore, since electrode fingers of MSCs are parallel in a plane and the thickness can be reduced, in-plane MSCs will be readily compatible with other mi- croelectronic unites to obtain the multifunctional integrated devices [17–20]. Therefore, developing in-plane MSCs with AC line filtering function to replace the bulky AECs will greatly contribute to the min- iaturization of the electronic systems [1–3]. Recently, great efforts have been made in designing in-plane MSCs with AC line filtering [13,21–28]. For instance, in-plane MSCs based on an azulene-bridged coordination polymer framework (PiCBA) were achieved by a facile layer-by-layer method and displayed an excellent AC line-filtering performance (-73° at 120 Hz) [4]. Furthermore, since various portable electronic devices are moving towards flexible, stretchable, wearable, and miniaturized directions [29–33]. Flexible MSCs with AC line filtering have been designed on plastic substrate [34]. However, compared with flexibility, stretchability is more chal- lenging since they will endure larger strain [35–44]. Therefore, the stretchable MSCs with AC line filtering raised the demand for the electrode materials and device architectures of MSCs, resulting in that the fabrication of stretchable MSCs with AC line filtering remains a challenge [45]. In addition, to date, some stretchable electronic devices with different functions such as light-emitting diodes, transistors, smart http://dx.doi.org/10.1016/j.nanoen.2017.10.056 Received 29 May 2017; Received in revised form 22 October 2017; Accepted 26 October 2017 ⁎ Corresponding author. E-mail address: zqniu@nankai.edu.cn (Z. Niu). Nano Energy 42 (2017) 187–194 Available online 26 October 2017 2211-2855/ © 2017 Elsevier Ltd. All rights reserved. MARK