Flexible ultrathin organic electrochemical transistor (OECT)-based portable system for monitoring and stimulation of bladder muscle.

Patients with bladder underactivity experience difficulty in sensing bladder fullness and emptying the bladder efficiently, leading to chronic urinary retention. An implantable bidirectional device that combines capturing bladder smooth muscle activities with stimulation could enable closed-loop assistance and offer benefits compared to the common timed intermittent catheterization. Most existing bidirectional systems lean on passive metal electrodes as the interface, which provide no intrinsic signal amplification for low-amplitude bladder electromyography sensing and offer limited charge-injection capacity for effective and safe stimulation. Organic electrochemical transistors (OECTs) offer an attractive alternative with high sensitivity for biopotential measurements and effective stimulation capability due to their high-capacitance polymer channels. In this study, we used a custom-made portable system for a flexible ultrathin OECT array to shape a bidirectional recording and stimulation interface for bladder smooth muscle. We validate the system's recording and stimulation performance under ex vivo conditions by using an organ bath setup equipped with a commercial force transducer as a mechanical reference. The array recordings showed stable baselines during inactive periods and clear and repeatable low-frequency output changes that matched force changes during spontaneous muscle contractions. The system also delivered programmed pulse trains that consistently triggered measurable contractions in the muscle, proving its reliable stimulation capability. These findings establish a practical foundation for OECT-enabled closed-loop bladder monitoring and stimulation and support the broader use of active organic bioelectronics as bidirectional interfaces for soft and dynamic organs.