Long-Range Telemetric Smart Orthodontic Bracket with CMOS-Integrated 3D Wirebonder-Fabricated Microcoils

This paper reports a novel telemetric smart bracket (TSB) for in vivo force/moment measurements during clinical orthodontic applications. The prototype implements a novel microcoil design resulting in a significant increase of the transmission distance compared to the previous state-of-the-art TSB. Using an automatic wirebonder, the microcoil is wound around an SU-8 post attached to the CMOS sensor wafer. For the first time, thus, 3D wirebonder-fabricated microcoils were integrated on a CMOS substrate, without compromising CMOS functionality. The augmented CMOS system serves here as a force/moment measurement device with six-degree-of-freedom (
$f_{x}, f_{y}, f_{z}, m_{x},\ m_{y},\ m_{z}$
) functionality. The achieved transmission distance, i.e. coil-to-coil distance, was thereby increased by 80% compared to the best previous design to 5 mm, without the need for the system to exceed the severe size constraints of
$2\times 2.8\times 1\ \mathrm{mm}^{3}$
defined by the bracket dimensions. The increased transmission distance allows uncritical contactless system powering and readout.