Liquid 3D Bioelectronics for Diagnosis and Therapeutic Stimulation in Cardiovascular Disease

Accuracy in recording the electrocardiograms (ECGs) is essential for the diagnosis and treatment of cardiovascular diseases such as arrhythmia, bradycardia, or atrial fibrillation. Previous studies have been conducted for accurate monitoring of ECGs, but existing devices using planar, rigid materials with high moduli (>1 GPa) have a mechanical mismatch in interface with the biological tissues (~100 KPa). This causes various problems such as lowering the quality of ECGs, resulting in immune responses and damaging the tissue during long-term recording. Additionally, the epicardium layer of the heart adjoining the myocardium, where most planar devices are attached, restricts the clear recording of the ECGs. Therefore, for precise and long-term recording, the development of a tissue-like and injectable three-dimensional (3D) device that can reach the myocardium to reduce undesirable noise levels is important. Here, we demonstrate the liquid 3D bioelectronics based on microneedle structure for both functions of cardiac diagnosis and therapeutic stimulation, with their tattooable, injectable, and biocompatible properties. The fluidity of these liquid 3D microneedles is beneficial in preventing tissue injury by offering reliable operations. Through an in-vivo experiment with a rabbit model, we confirmed that the liquid 3D microneedles are capable of monitoring clearer signals compared to the conventional planar electrodes, and of transmitting electrical stimulus to a live heart for recovering from cardiac disorder to a normal rhythm.