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66 PCB007 MAGAZINE I NOVEMBER 2023 If employers can quickly provide employees with the tools needed to speak their common language with one or two simple programs, both the employer and employee will reap the benefits. What tools can your company use to reduce the terminology barrier? PCB007 Paige Fiet is a process engineer at TTM-Logan, and in the IPC Emerging Engineer Program. To read past columns, click here. reference guide for inspection, IPC-A-600K, "Acceptability of Printed Boards," is a good place to start. Conclusion Terminology can be troubling for new hires but there are ways to prevent it from becom- ing a barrier between employer and employ- ees. Unfortunately, most employees will not come into a PCB manufacturing environment from another industry or higher education with the terminology base needed to succeed. Researchers have developed a new method for making tiny stretchable antennas from a hydrogel and liquid metal. The antennas could be used in wearable and flexible wireless electronic devices to provide a link between the device and external sys- tems for power delivery, data processing and com- munication. "Using our new fabrication approach, we demon- strated that the length of a liquid metal antenna can be cut in half," said Tao Chen from Xi'an Jiaotong University in China. "This may help downsize wear- able devices used for health monitoring, human activity monitoring, wearable computing and other applications, making them more compact and com- fortable." In the Optica Publishing Group journal Optics Express, the researchers describe their new tech- nique, which involves injecting eutectic gallium- indium—a metal alloy that is a liquid at room tem- perature—into a microchannel created with a sin- gle-step femtosecond-laser ablation process. They used this method to create an antenna measuring 24 mm × 0.6 mm × 0.2 mm embedded into a 70 mm × 12 mm × 7 mm hydrogel slab. "Stretchable and flexible antennas could be use- ful for wearable medical devices that monitor tem- perature, blood pressure and blood oxygen, for example," said Chen. "Separate mobile devices could connect to a larger control unit via the flexi- ble antennas—which would transfer data and other communications—forming a wireless body-area network. Since the resonance frequencies of the flexible antennas vary with applied strain, they could potentially also be used as a wearable motion sensor." Making a Stretchable Antenna To demonstrate the new fabrication approach, the researchers prepared stretchable dipole anten- nas and measured their reflection coefficients at dif- ferent frequencies. These experiments showed that the pure hydrogel reflects almost all the incident electromagnetic wave energy, while the liquid metal dipole antenna embedded in hydrogel radiates most of the incident electromagnetic wave effec- tively into free space, with less than 10% reflected at the resonance frequency. They also showed that by varying the applied strain from 0 to 48%, the res- onant frequency of the antenna can be tuned from 770.3 MHz to 927.0 MHz. (Source: OPTICA) Researchers Use Liquid Metal and Laser Ablation to Create Stretchable Miniature Antennas