A Wearable ECG Monitoring System Using Microneedle Electrodes for Small Animals

The electrocardiogram (ECG) is an effective tool for monitoring various health conditions, and animal studies using ECG have uncovered new information about complex diseases. However, monitoring electrophysiological signals in small animals such as mice has been challenging. In this study, we present a simple, minimally invasive, and inexpensive ECG measurement sensory system for mice that offers real-time data acquisition while performing surgery. We developed a miniaturized, wearable ECG monitoring device that utilizes miniature-sized, rigid metal-type microneedle electrodes with a skin–electrode contact resistivity of 20 $\text{k}\Omega $ at 10 Hz, which is lower than commercial Ag/AgCl electrodes used in human ECGs. The device, excluding the battery, is less than 50 mm3 in size and amplifies and converts the waveform, which is transmitted to a personal cell phone or laptop. We developed a smartphone application to display the real-time ECG waveform and heart rate without the need for additional equipment. The recorded data can be retrieved for further analysis, and the real-time display feature can be used to monitor an animal's condition during surgery. We validated this method by inducing a photothrombotic stroke in an ICR mouse to study ECG and HR parameters in an animal stroke model.