Abstract: As an important part of flexible micro and nano electronic devices, high-precision flexible transparent circuit has been widely used in 5G/6G flexible transparent antenna, wearable devices, transparent electric heating film, flexible transparent electronics and other fields. However, the high efficiency, low cost and flexible manufacturing of high density circuits with high resolution, high optoelectronic and mechanical performance, especially copper based circuits, is a major problem in current research. To address this challenge, a new method for manufacturing high-precision flexible transparent copper based circuits by combining electric field driven micro 3D printing and wet etching technology to achieve additive/subtractive composite manufacturing is proposed. It not only achieves low-cost and flexible printing of high-resolution and high-precision etching masks, but also further reduces the linewidth of ultra-fine circuits through rapid etching processes.The basic forming principle and key technology realization are described. Through experiments, the influence of main process parameters on circuit morphology and performance is revealed, studied the influence law of etching speed and explored the controllability of two stages in the etching process (fast etching and side etching), and precisely controlled the side etching process. Combined with optimized printing parameters and precise control of side etching speed, the manufacturing of flexible transparent circuits with a minimum line width of 2.4 μm and a minimum line spacing of 4 μm is achieved. The resistivity of the typical sample is 4×10^-6 Ω·cm, when the light transmittance is as high as 87.65% (550 nm wavelength, including substrate), the sheet resistance is only 3.58 Ω/sq, simultaneously possessing excellent mechanical stability and electric heating performance. The prepared high-density flexible transparent interdigital electrode has excellent sensitivity and can detect dilute sulfuric acid solutions with a minimum concentration change of only 1 nmol/L at a frequency of 100-10 000 Hz. This method provides a new solution for high efficiency and low cost manufacturing of high density copper based flexible transparent circuits, and shows a good industrial application prospect.

Key words: electric-field-driven micro 3D printing, flexible transparent circuit, hybrid manufacturing, additive and subtractive manufacturing, high density flexible circuit