Evaporative cooling for low-cost monitoring of flow of cerebrospinal fluid through shunts in patients with hydrocephalus

Hydrocephalus, a neurological disorder caused by an abnormal accumulation of cerebrospinal fluid (CSF) in the brain, manifests in symptoms such as headaches, blurred vision, and balance issues. While ventriculoperitoneal shunting is a common treatment, it has high failure rates, especially in pediatric patients. Recent progress in continuous, non-invasive monitoring using skin-mounted sensors based on anemometric techniques and transient plane source methods offer significant promise. Here, we introduce an advanced device of this general type, configured for ultralow power operation and cost-effective construction. The innovation involves replacing heating elements with passive cooling mechanisms driven by water evaporation, thereby reducing the need for high-capacity battery power. Localized cooling at the shunt position (ΔT_skin ∼6 °C) enables flow measurements by creating differential temperature changes in upstream and downstream regions. Quantitative models of thermal transport and systematic experimental studies enable optimized design choices. A compact device with Bluetooth Low Energy (BLE) capabilities and a small battery allows both intermittent evaluations and continuous monitoring. Additional measurements confirm capabilities in accurate flow measurements using passive, non-electronic skin patches, where readout occurs based on colorimetric evaluations of thermochromic liquid crystal (TLC) arrays by digital image analysis. These results provide versatile, cost-effective, and accessible shunt monitoring options suitable for use even in the most resource-constrained regions of lower- and middle-income countries.