Picture: Johns Hopkins APL
Researchers at the Johns Hopkins Applied Physics Laboratory are using advanced 3D printing and shape memory alloys to develop antennas that deform under temperature control. This technology opens up new possibilities for flexible wireless applications in military research and industry.
The shape of an antenna significantly influences its operating parameters, and until now these were unchangeable after production. The new antenna, however, adapts dynamically to support a wider range of radio frequencies. This could replace several rigid antennas and significantly increase flexibility in frequency management. The idea came from engineer Jennifer Hollenbeck, inspired by shape-shifting in the science fiction series The Expanse.
“I have spent my career working with antennas and wrestling with the constraints imposed by their fixed shape,” she said. “I knew APL had the expertise to create something different.”
The development focused on the use of Nitinol, an alloy of nickel and titanium that can change its shape depending on the temperature. The challenge was to print this alloy precisely in complex structures, as it reacts to the heat generated during the process.
“It turned out to be a really complicated design, and it didn’t work as well as I would have liked,” Hollenbeck said.
Through extensive experimentation and modifications to the nickel-titanium ratio, they eventually succeeded in creating a flat spiral antenna that unfolds into a conical shape when heated. A newly developed current conductor ensured that the antenna could be brought to the required temperature without compromising radio performance.
“We have a lot of experience optimizing processing parameters and designs for alloys, but this was a step beyond,” explained additive manufacturing engineer Samuel Gonzalez. “There aren’t many people out there, if anyone, printing this material, so there’s no recipe for how to process it.”“We made shrapnel in the printer a few times because the antenna is trying to change shape as you’re printing it, due to the heat,” added colleague Mary Daffron. “It wants to peel apart.”
The technology has the potential to enable compact and adaptable communication systems. APL is now seeking patents for the antenna and the underlying processes.
“The shape-shifting antenna capability that has been demonstrated by this APL team will be a game-changing enabler for many applications and missions requiring RF adaptability in a low-size and -weight configuration,” said APL Chief Engineer Conrad Grant. “This is yet another powerful example of the innovation that occurs at the Laboratory through motivated, highly capable, multidisciplinary teams.”
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