A novel design to power the micro-ECG sensor implanted in adult zebrafish

Heart diseases have been the leading cause of death in the developed world, partially due to failure to adequately replace lost ventricular myocardium from ischemia-induced infarct. Adult mammalian ventricular cardiomyocytes have a limited capacity to divide, and this proliferation is insufficient to overcome the significant loss of myocardium from ventricular injury. Unlike mammalian hearts, zebrafish (Danio rerio) hearts fully regenerate after 20% ventricular amputation in 2 months, thereby providing a genetically tractable model system for heart regeneration investigations. Recently, electrocardiogram (ECG) assessment in zebrafish has showed promise as an alternative method to study heart regeneration and heart diseases; however, all existing approaches involving the use of anesthesia drugs are inadequate to provide intrinsic ECG signals. Towards a wireless ECG platform, we use the wireless power transfer (WPT) technique via inductive coupling to power an ECG sensor implanted in an adult zebrafish. The transmitter coil is a solenoid wound around a customized cylindrical housing while the compact receiver solenoid on the fish is modified to counter misalignment issues. The ECG data are sent to the external unit via backscattering in the form of load modulation using the same inductive link. Our system enables continuous monitoring of freely-swimming fish without disrupting their normal activities. An adaptive tuning method is used and power transfer efficiency (PTE) is characterized using a vector network analyzer (VNA) via S-parameter measurement.