World's smallest single-chip system that can be injected into the body with a needle

As electronics continue to miniaturize, they are providing us with many new ways to monitor and improve our health, and even expanding some very exciting possibilities. Recently, engineers from Columbia University demonstrated an extreme version of this technology by developing the smallest single-chip system ever made, which can be implanted under the skin with a hypodermic needle to measure temperature inside the body, and could even be expanded for more uses.

Above: the world's smallest single-chip system at the tip of a hypodermic needle.

Currently, from ladybug-sized implants that track oxygen levels in the body's deep tissues to tiny "neural dust" sensors that monitor neural signals in real time, scientists have taken a big step forward in the functionality of microelectronic devices. This time, the implant, developed by engineers at Columbia University, is the world's smallest single-chip system, a full-featured electronic circuit with a total volume of less than 0.1 cubic millimeters, breaking new ground.

That makes it as small as a dust mite and much smaller than the world's smallest computer. It is a cubic device of 0.3 millimeters (0.01 inches) on each side. This microchip can only be seen under a microscope, and it took some innovative thinking to make it, especially in the way it communicates and is powered.

Typically, small electronic devices might use radio frequency (RF) modules to send and receive electromagnetic radio signals, but these wavelengths are too large to be used in such a small device. On the other hand, the wavelength of ultrasound is much smaller at a given frequency because the speed of sound waves is much lower than the speed of light at which electromagnetic waves propagate. So the team installed a piezoelectric transducer that acts as an "antenna" to wirelessly power and communicate via ultrasound.

This, combined with an onboard low-power temperature sensor, transformed the chip into a probe for real-time temperature sensing, allowing it to monitor body temperature and temperature fluctuations driven by ultrasound therapy applications. The ability of this implant was demonstrated in experimental live rats, where it was used for ultrasonic nerve stimulation, injected intramuscularly via a syringe, and up to seven implants could be implanted into the experimental rats at a time.

Eventually, scientists envision implanting this chip into the body and then wirelessly transmitting the measured information via ultrasound. In its current form, this is limited to body temperature, but in the future it might also include information on blood pressure, blood sugar levels and respiratory function.

The scientists leading the research said, "We want to see how far we can scale down the functionality of the chip. This is the new concept of 'chip-as-a-system' -- it's a single chip that doesn't need anything else to be a complete electronic system. This should be revolutionary for the development of wireless miniature implantable medical devices that can sense different things, be used for clinical applications, and eventually be approved for human use."

The study was published in the journal Science Advances.

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