We propose a new packaging process for an implantable blood pressure sensor using ultrafast laser micro-welding. The sensor is a membrane type, passive device that uses the change in the capacitance caused by the membrane deformation due to applied pressure. Components of the sensor such as inductors and capacitors were fabricated on two glass (quartz) wafers and the two wafers were bonded into a single package. Conventional bonding methods such as adhesive bonding, thermal bonding, and anodic bonding require considerable effort and cost. Therefore CO₂ laser cutting was used due to its fast and easy operation providing melting and bonding of the interface at the same time. However, a severe heat process leading to a large temperature gradient by rapid heating and quenching at the interface causes microcracks in brittle glass and results in low durability and production yield. In this paper, we introduce an ultrafast laser process for glass bonding because it can optimize the heat accumulation inside the glass by a short pulse width within a few picoseconds and a high pulse repetition rate. As a result, the ultrafast laser welding provides microscale bonding for glass pressure sensor packaging. The packaging process was performed with a minimized welding seam width of 100 μm with a minute. The minimized welding seam allows a drastic reduction of the sensor size, which is a significant benefit for implantable sensors. The fabricated pressure sensor was operated with resonance frequencies corresponding to applied pressures and there was no air leakage through the welded interface. In addition, in vitro cytotoxicity tests with the sensor showed that there was no elution of inner components and the ultrafast laser packaged sensor is non-toxic. The ultrafast laser welding provides a fast and robust glass chip packaging, which has advantages in hermeticity, bio-compatibility, and cost-effectiveness in the manufacturing of compact implantable sensors.

Lithium-ion batteries are widely used for many applications such as portable electronic devices and Electric Vehicles, because they have lighter weight, higher energy density, higher power density, and a higher energy-to-weight ratio than other types of batteries. Conventional contact-based cutting technology may be inefficient whenever cell design is changed since lithium-ion battery cells are not standardized. Furthermore, the conventional cutting may result in process instability and a poor cut quality due to the tool wear so that it leads to short circuits and local heat generation. These process instability and inefficiency may be solved by laser cutting due to advantages such as clean cutting edge, less deformation, applicability to almost all materials, possibility of precision processing, and easy modification of cutting path. Despite the importance of the laser cutting research, no clear definition of cutting widths has been presented, and there is lack of knowledge to understand the effect of laser parameters on cutting widths. Therefore, this research examines the surface of cathode cut by a laser and defines cutting widths such as top width, melting width, and kerf width. The relationship between the laser parameters and cutting characteristics with defined widths are studied. When the volume energy is less than $6.0172\times {10}^{10}\mathrm{J}/{\mathrm{m}}^3$ , no active electrode material is removed. When the laser power is greater or equal to 100 W, both the top and melting widths are clearly observed. The laser power of 50 W can selectively ablate the active electrode material with the material removal rate of 32.14–55.71 ${\mathrm{mm}}^3/\min$ . The threshold volume energy to fully penetrate the 50 μm-thick current collector is between $9.6275\times {10}^{10}–8.0229\times {10}^{10}\mathrm{J}/{\mathrm{m}}^3$ . All clearance width is less than 20 μm, while the clearance width interestingly exceeds 20 μm when the laser power is 200 W. The effect of material properties on heat transfer using the one dimensional transient semi-infinite conduction model is investigated. In addition, five types of physical characteristics are defined and discussed.