## 3 Results and Discussion
The CNTs are pressed into the molten pool under the action of laser light pressure [39]. When the laser irradiation is stopped, the CNTs rapidly anneal at the junction of the electrodes, thereby firmly embedding the CNTs in the metal electrodes. In order to evaluate the electrical properties of the contact before and after the connection, we conducted electrical performance tests on the two ends of the contact between the CNTs and the electrodes before and after the laser irradiation. We determined that there were a small number of SWCNT bundles composed of multiple SWCNTs or individual SWCNTs and SWCNT bundles connected together in the SDS solution in the experiment. After depositing on the electrodes, the SWCNT bundles might bridge to the electrodes, which may have a certain degree of influence on the test results. In this experiment, we used the method of SEM to observe the presence of SWCNT bundles, irradiating the SWCNT bundles with a low energy density (about 7.619 mJ/cm\({}^{2}\), irradiation duration of 60 s), so that the SWCNT bundles were destroyed, while the individual SWCNTs deposited between the two electrodes was retained. It was found by SEM that a part of the SWCNTs bundle was broken, and individual SWCNTs or stable SWCNT bundles basically remained, which ensured that the test results were not affected by the quality of SWCNT bundles. Therefore, the \"before irradiation\" mentioned in this article, unless otherwise specified, indicates that the state after the influence of the SWCNT bundles has been removed. The removal of unstable SWCNTs by laser irradiation is still under investigation. The resistance at both ends of the measured electrodes is typically several hundred thousand ohms at room temperature before laser irradiation. After laser irradiation, the resistance is reduced to tens of thousands of ohms to several thousand ohms. For the purpose of investigating the effect of laser energy density on the connection effect, we used different laser power parameters to irradiate the contact area and characterized the effect of connection through the I-V curve. When the laser energy density is about 11.429 mJ/cm\({}^{2}\), the resistance at the contact is reduced from 104 k to 34.2 k ohms. When the laser energy density increases to 13.810 mJ/cm\({}^{2}\), the resistance at the contact decreases 5.5 k ohms and then tends to saturate at 5.5 k ohms. Increasing laser density continually, a certain degree of damage begins to occur at the edge of the metal electrode; part of the CNTs are struck and thrown out, and the resistance at both ends of the electrode rises sharply. Figure 4a shows an I-V plot of one of the samples before and after laser irradiation, where the black line represents before laser irradiation and the red line represents after laser irradiation. It can be very clearly observed that the contact resistance after laser irradiation has decreased significantly compared to before laser irradiation. Figure 4b shows the change in resistance of multiple samples before and after laser irradiation. The resistance of all CNTs to metal electrodes contact resistance is based on the calculation of the I-V curve when the measured voltage is 5 V. It can be seen from the figure that although the contact resistances of the samples are different, the contact resistance has decreased to some extent after laser irradiation, indicating that the SWCNTs form a reliable connection with the metal electrodes under laser irradiation. At the same time, measurements were carried out after storage for 1 month under laboratory conditions at room temperature and atmospheric pressure, and the results were almost unchanged, indicating that the contact points were stable in the air for a long period of time. Figure 4c shows the tendency of the resistance change across the CNTs under different laser energy irradiation. It was concluded that the significant decrease in the resistance at the contact may be due to an increase in the contact area between the CNTs and the electrodes [40].