This senior design project develops a compact, smart flow sensor to monitor cerebrospinal fluid (CSF) flow in hydrocephalus shunt systems. Hydrocephalus occurs when excess CSF accumulates in the brain, increasing intracranial pressure and potentially causing severe neurological damage. Although shunts relieve this pressure by redirecting CSF to other parts of the body, they frequently fail due to blockage or mechanical malfunction. Because shunts are implanted, failure is often detected only after symptoms become severe. Our project addresses this challenge by creating a sensor that quantitatively measures CSF flow and enables earlier detection of shunt malfunction. The device uses a reflection-based optical sensing system. As CSF flows through the shunt, it enters a transparent chamber containing a flexible diaphragm membrane that deflects proportionally to flow rate. A light-emitting diode (LED) illuminates the diaphragm, and the intensity of light reflected to a photodetector changes as the diaphragm bends. By calibrating reflected light intensity to known flow conditions, the system can determine CSF flow rate in real time. The chamber is CNC-milled from transparent, biocompatible polymethyl methacrylate (PMMA), while the diaphragm is fabricated from biocompatible polydimethylsiloxane (PDMS) using molding techniques and coated with a thin gold layer to enhance reflectivity. A compact microcontroller processes the photodetector signal and wirelessly transmits data via Bluetooth Low Energy (BLE) to an external device. All electronics are integrated onto a custom printed circuit board (PCB) and use low-power sleep–wake cycles to extend device lifetime. This technology could improve patient safety by enabling earlier detection of shunt failure and reducing the need for emergency surgical intervention.