Minimally Invasive Square-based Temporal Interference Stimulation IC for Neuromodulation with Enhanced E-field Delivery.
Temporal interference stimulation (TIS) has emerged as a promising neuromodulation technique for achieving deep brain stimulation (DBS) with reduced invasiveness. However, conventional transcutaneous TIS suffers from the current shunting effect from the scalp, which limits the electric-field (E-field) delivery to the target region. In addition, conventional sine-based TIS systems rely on noise-sensitive and linearity constrained analog waveform synthesizers. To address these limitations, this work presents a minimally invasive square-based TIS integrated circuit (IC) that simultaneously achieves enhanced E-field delivery and fully digital stimulation waveform generation. The system generates temporal interference (TI) envelopes by digitally controlling an ON/OFF H-bridge driver, significantly simplifying circuit implementation with a gate-driving overhead of only 250 nW per channel. It also delivers higher root-mean square (RMS) energy than sine-based TIS under identical peak-current conditions. The stimulation IC is integrated within a 0.96 mm2 active area. Experimental tissue phantom measurements show that the proposed system achieves a 2.01 dB higher PSD at Δf and a time-domain envelope amplitude approximately 1.27 times that of sine-based TIS, demonstrating enhanced Δf envelope delivery. The proposed system supports long-term operation (1 s-1 h) and real-time parameter control through an inductive-link interface. It also achieves one of the lowest reported system complexities. These results demonstrate the feasibility of a programmable wireless TIS system for the proposed minimally invasive on-skull configuration.