Yaqiang Ji,Yuan Zhang,Jiaqi Zhu,Pai Geng,Jonathan E. Halpert,Liang Guo
Flexible pressure sensors play an indispensable role in flexible electronics. Microstructures on flexible electrodes have been proven to be effective in improving the sensitivity of pressure sensors. However, it remains a challenge to develop such microstructured flexible electrodes in a convenient way. Inspired by splashed particles from laser processing, herein, a method for customizing microstructured flexible electrodes by femtosecond laser-activated metal deposition is proposed. It takes advantage of the catalyzing particles scattered during femtosecond laser ablation and is particularly suitable for moldless, maskless, and low-cost fabrication of microstructured metal layers on polydimethylsiloxane (PDMS). Robust bonding at the PDMS/Cu interface is evidenced by the scotch tape test and the duration test over 10 000 bending cycles. Benefiting from the firm interface, the developed flexible capacitive pressure sensor with microstructured electrodes presents several conspicuous features, including a sensitivity (0.22 kPa −1 ) 73 times higher than the one using flat Cu electrodes, ultralow detection limit (<1 Pa), rapid response/recovery time (4.2/5.3 ms), and excellent stability. Moreover, the proposed method, inheriting the merits of laser direct writing, is capable of fabricating a pressure sensor array in a maskless manner for spatial pressure mapping.
The electrochemical redox and electrodeposition behaviors of nitrosyl ruthenium in nitric acid solution were systematically investigated by electrochemical quartz crystal microbalance analysis and cyclic voltammetry. The results show that the reduction of ruthenium is carried out in steps. The reduction current of Ru(III) to Ru(II) was observed at 0.05 V. A cathode current peak was recorded between −0.2 and −0.5 V, accompanied by a significant mass gain, which was confirmed to be the electrodeposition of metal ruthenium. During the oxidation process, the deposited Ru was slowly oxidized at a low oxidation potential, and the Ru dissolved violently at 0.75 V, resulting in a rapid degradation of the surface quality of the electrode. The electrodeposition kinetic parameters and nucleation growth mechanism of ruthenium in the nitric acid system were revealed by means of electrochemical measurement and model fitting, and the electrocrystallization of ruthenium was determined as instantaneous nucleation. After potentiostatic deposition on different substrates, it is found that the coating on the glassy carbon (GC) sheet presents a crumbly and coiled structure, while the surface of the coating on the Pt sheet is smoother and has a neat fracture edge.
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