Fig. 1 Miniaturized, monolithically integrated, fully wireless temperature-sensing motes with ultrasound powering and data communication. (A) A deconstructed schematic illustration of the major components of a mote, including a CMOS temperature sensor chip with two exposed Al pads, a microscale PZT transducer covered in Au on both sides, an anisotropic conductive film (ACF), and a Cu layer. (B) An SEM image of the mote, where the PZT transducer is monolithically integrated on the surface of the sensor chip (photo credit: Jeffrey Elloian, Columbia University). The mote is 300 μm wide, 380 μm long, and 570 μm thick (0.065 mm3); it weighs 0.3 mg. (C) A picture of a mote placed on a U.S. dime showing the relative size scale (photo credit: Chen Shi, Columbia University). (D) A mote placed at the tip of an 18-G needle (inner diameter, 0.84 mm, outer diameter, 1.28 mm; photo credit: Victoria Andino-Pavlovsky, Columbia University). (E) Seven motes loaded in a 1-ml syringe filled with PBS solution (photo credit: Victoria Andino-Pavlovsky, Columbia University). (F) The system diagram demonstrating the operating principles of such a mote. A Vantage 256 system (Verasonics Inc.) produces a customized ultrasound signal through an L12-3v probe. Such a signal provides power to and receives data from a mote. The embedded sensor chip contains a front-end block to convert the incoming AC signal from the on-chip transducer into a stable DC supply for the rest of the chip, a temperature-sensing block to perform temperature measurements, and a modulation block to transfer the temperature information back to the ultrasound source by actively modifying the input impedance of the integrated PZT transducer.
Fig. 2 In vitro characterization with two motes embedded in chicken tissues. (A) An ultrasound image showing the mote embedded in chicken tissue (photo credit: Chen Shi, Columbia University). (B) Waveform of the ultrasound signal used to power up and communicate with the mote. (C) Acoustic backscattering data obtained at 37°C for 1.28 s showing the signal and RMS noise levels. (D) Temperature curves for two motes from 25° to 50°C.
Fig. 3 In vivo characterization with motes implanted on the brain and in the hindlimb for measuring core body temperature. (A) The experimental setup with a mote implanted on the brain of a mouse (photo credit: Chen Shi, Columbia University). (B) A continuous temperature recording with the mote implanted on the brain compared to the reference temperature. (C) The experimental setup with a mote implanted in the hindlimb of a mouse (photo credit: Chen Shi, Columbia University). (D) A continuous temperature recording with the mote implanted in the hindlimb compared with the reference temperature.
Fig. 4 In vivo characterization with motes implanted at the sciatic nerve for temperature monitoring during FUS stimulation. (A) The experimental setup for measuring the EMG responses in the leg of a mouse with FUS stimulation at the sciatic nerve (photo credit: Chen Shi, Columbia University). (B) EMG signals recorded with FUS stimulation at the sciatic nerve. (C) Implantation of two motes at the sciatic nerve (photo credit: Victoria Andino-Pavlovsky, Columbia University). Inset: Cartoon illustration of the implantation strategy. (D) Illustration of applying FUS from beneath the sciatic nerve (photo credit: Victoria Andino-Pavlovsky, Columbia University). (E) The experimental setup to measure temperature increases with FUS stimulation (photo credit: Chen Shi, Columbia University). (F) The temperature variations of two implanted motes under four different FUS stimulation intensities in comparison to their self-heating effects measured in vitro.
Supplementary Materials
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/7/19/eabf6312/DC1
Additional Files
Supplementary Materials
Application of a sub–0.1-mm3 implantable mote for in vivo real-time wireless temperature sensing
Chen Shi, Victoria Andino-Pavlovsky, Stephen A. Lee, Tiago Costa, Jeffrey Elloian, Elisa E. Konofagou, Kenneth L. Shepard
This PDF file includes:
- Notes S1 to S4
- Figs. S1 to S11
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