A 10 mm3 Inductive Coupling Radio for Syringe-Implantable Smart Sensor Nodes

We present a near-field radio system for a millimeter-scale wireless smart sensor node that is implantable through a 14-gauge syringe needle. The proposed system integrates a radio system on chip and a magnetic antenna on a glass substrate within a total dimension of 1 × 1 × 10 mm
³
. We demonstrate energy-efficient active near-field wireless communication between the millimeter-scale sensor node and a base station device through an RF energy-absorbing tissue. The wireless transceiver, digital baseband controller, wakeup controller, on-chip baseband timer, sleep timer, and MBUS controller are all integrated on the SoC to form a millimeter-scale sensor node, together with a 1 × 8 mm
²
magnetic antenna fabricated with a 1.5-μm-thickness gold on a 100 μm-thickness glass substrate. An asymmetric link is established pairing the sensor antenna with a codesigned 11 × 11 cm
²
base station antenna to achieve a link distance of up to 50 cm for sensor transmission and 20 cm for sensor reception. The transmitter consumes a 43.5 μW average power at 2 kb/s, while the receiver power consumption is 36 μW with a -54 dBm sensitivity at 100 kb/s. When powered by a 1×2.2 mm
²
thin-film battery (2 μAh, 4.1 V), the designed system has a two week expected lifetime without battery recharging when the system wakes up and transmits and receives 16 b data every 10 min.