Low-powered implantable devices activated by ultrasonic energy transfer for physiological monitoring in soft tissue via functionalized electrochemical electrodes

Ultrasounds (US) are one of the most used imaging techniques in medicine for assessing the physiological and pathological state of soft tissue. Apart from therapeutic applications, most of the interaction of the acoustic beams with tissues occur passively and without substantial modification to the physiology of the latter. However, US can also be used to remotely power implantable devices with sensing capabilities. In this study, we propose small-form devices interfaced with functionalized electrochemical electrodes for the detection of pH and lactate levels, powered by ultrasounds and data transmission through a Frequency Shift Keying (FSK) modulation technique. A custom-made piezoelectric transducer is responsible for converting the acoustic waves into electrical voltage at the device with operational levels as low as 0.5 V (power consumption of 10 ?W) obtained from implantation distances of 50 mm inside tissue. This conjugated with the high sensitivity of the developed electrochemical sensors allows to detect and transmit local parameter variations below 0.1 pH (4.2 mV) and 1 mM lactate (70 nA). Potential applications include real-time access to intrabody tissue monitoring postoperatively, with the view of assessing proper soft tissue healing or infection detection by bacteria, as well as tissue cancer screening in structures such as the human breast.

Automated summary

Ultrasounds can be used to remotely power implantable devices for pH and lactate level detection. By combining a custom-made piezoelectric transducer with highly sensitive electrochemical sensors, low power consumption local parameter variation detection and transmission is achieved in experimental conditions.