Bladder Control Implants

This chapter presents a system of bladder neuromodulation and a method for the control of the variable burst biphasic pulse of a bladder stimulator. The stimulator is used to pass current through the tissue and to generate useful action potentials. The binary-weighted digital-to-analog converter combined with a current mirror has been employed as a microstimulator because of its higher linearity without requiring the decoding of digital inputs. Two algorithms including burst pulse generation algorithm and slow reversal with interphase delay pulse generation algorithm are present. Given that the use of a biphasic pulse could prevent ion-charge accumulation in tissues, two pairs of switches controlled by different clock phases are implemented to provide the biphasic electrical stimulation pulses. The presented method has been verified on FPGA implementation to demonstrate the proposed algorithms which is helpful for the future implementation in the integrated circuits. In this study, the pulse frequency can be programmed between 1.49 and 47.66 Hz, the burst frequency can be controlled from 190.8 to 763 Hz, and the pulse width can be adjusted between 21 and 325 µs. These stimulation parameters are adapted by the clock divider and by the number of controlled bits in the digital circuits. In the future, the microstimulator with controlled algorithm can be integrated with power interface and sensing channel as an implantable device for animal study.