Flexible resistive random access memory (RRAM) has shown great potential in wearable electronics. With tunable multilevel resistance states, flexible memristors could be used to mimic the bio-synapses for constructing high-efficient wearable neuromorphic computing system. However, the flexible substrate has intrinsic disadvantages including low-temperature tolerance and poor complementary metal-oxide-semiconductor (CMOS) compatibility, which limit the development of flexible electronics. The physical vapor deposition (PVD) fabrication process could prepare RRAM without requirement of further treatment, which greatly simplified preparation steps and reduced the production costs. On the other hand, forming process, as a common pre-programing operation in RRAM, increases the energy consumption and limits the application scenarios of RRAM. Here, a NiO-based forming-free RRAM with low set voltage was fabricated via full PVD technique. The flexible device exhibited reliable resistive switching characteristics under flat state even compressive and tensile states (R = 10 mm). The tunable multilevel resistance states (5 levels) could be obtained by controlling the compliance current. Besides, synaptic plasticities also were verified in this device. The flexible NiO-based RRAM shows great potential in wearable forming-free multibit memory and neuromorphic computing electronics.

柔性电阻式随机存取存储器（RRAM）在可穿戴电子产品中显示出巨大潜力。具有可调的多级电阻状态，柔性忆阻器可用于模拟生物突触，以构建高效的可穿戴神经形态计算系统。然而，柔性基板具有固有的缺点，包括低温耐受性和差的互补金属氧化物半导体（CMOS）兼容性，这限制了柔性电子学的发展。物理气相沉积（PVD）制造工艺无需进一步处理即可制备RRAM，从而大大简化了制备步骤并降低了生产成本。另一方面，作为RRAM中常见的预编程操作，形成过程增加了能量消耗并限制了RRAM的应用场景。这里，通过全PVD技术制造了具有低设定电压的基于NiO的免成型RRAM。该柔性器件在平坦状态甚至压缩和拉伸状态下均表现出可靠的电阻切换特性（R = 10毫米）。可以通过控制顺应电流来获得可调的多级电阻状态（5级）。此外，该装置还验证了突触可塑性。基于NiO的灵活RRAM在可穿戴免成型多位存储器和神经形态计算电子学中显示出巨大潜力。