A passive, biocompatible microfluidic flow sensor to assess flows in a cerebral spinal fluid shunt

Abstract

Abstracts Hydrocephalus is a disease in which a buildup of cerebral spinal fluid in the ventricles of the brain can cause brain trauma and death if untreated. The current standard of treatment is to insert a shunt to drain the fluid from the ventricles in the brain to the abdomen. A shortcoming of this approach is that the shunt may get clogged, and this failure is not easily detected. We have developed a novel microfluidic sensor for application in a cerebrospinal fluid shunt. The sensor system is totally passive and no implanted electronics are required. The sensor itself is a bending based cantilever made from biocompatible polydimethylsiloxane (PDMS) and is capable of measuring flow rates from 20 ml/hr to 120 ml/hr, which is the indicated range for the flow rate of cerebral spinal fluid. The sensor is paired with an optical detection system that uses a small light spot to read the changes in sensor position due to flow. The light is input from outside the brain into the implanted optical system and the output light is measured by a camera external to the body. The sensor stability was verified by running cerebral spinal fluid over the cantilever continuously for two weeks. The ability of the sensor to measure pulsed flow and linearly increasing flow rates was also verified. All of the materials used for the device are biocompatible materials and are amenable for manufacturing and animal tests and clinical studies.