Miniaturized passive hydrogel check valve for hydrocephalus treatment

Design of a piezoelectrically actuated hydrocephalus shunt valve

Hydrocephalus is currently managed by using traditional mechanical passive shunts. Due to their nature, these shunts have fundamental shortcomings including an increase in patient shunt dependency, absence of fault detection, and over drainage due to lack of shunt proactivity. There is a scientific consensus that the way forward to address these issues is through what is termed a smart shunt. The core component of this system is the mechatronic controllable valve. A design of a valve which utilises both the passive nature of the classical valves and the controllability feature of the fully automated valves is presented in this paper. The valve consists of a fluid compartment, a linear spring, and an ultrasonic piezoelectric element. The valve is designed to operate on a 5 V supply, to drain up to 300 mL/h, and it has an operational range between 10 and 20 mmHg. The design produced is considered feasible as it takes into consideration the multiple operation conditions associated with such an implanted system.

Hydrogel Check-Valves for the Treatment of Hydrocephalic Fluid Retention with Wireless Fully-Passive Sensor for the Intracranial Pressure Measurement

Hydrocephalus (HCP) is a neurological disease resulting from the disruption of the cerebrospinal fluid (CSF) drainage mechanism in the brain. Reliable draining of CSF is necessary to treat hydrocephalus. The current standard of care is an implantable shunt system. However, shunts have a high failure rate caused by mechanical malfunctions, obstructions, infection, blockage, breakage, and over or under drainage. Such shunt failures can be difficult to diagnose due to nonspecific systems and the lack of long-term implantable pressure sensors. Herein, we present the evaluation of a fully realized and passive implantable valve made of hydrogel to restore CSF draining operations within the cranium. The valves are designed to achieve a non-zero cracking pressure and no reverse flow leakage by using hydrogel swelling. The valves were evaluated in a realistic fluidic environment with ex vivo CSF and brain tissue. They display a successful operation across a range of conditions, with negligible reverse flow leakage. Additionally, a novel wireless pressure sensor was incorporated alongside the valve for in situ intracranial pressure measurement. The wireless pressure sensor successfully replicated standard measurements. Those evaluations show the reproducibility of the valve and sensor functions and support the system’s potential as a chronic implant to replace standard shunt systems.

Three-Dimensionally Printed Microelectromechanical-System Hydrogel Valve for Communicating Hydrocephalus

Hydrocephalus (HCP) is a chronic neurological brain disorder caused by a malfunction of the cerebrospinal fluid (CSF) drainage mechanism in the brain. The current standard method to treat HCP is a shunt system. Unfortunately, the shunt system suffers from complications including mechanical malfunctions, obstructions, infections, blockage, breakage, overdrainage, and/or underdrainage. Some of these complications may be attributed to the shunts' physically large and lengthy course making them susceptible to external forces, siphoning effects, and risks of infection. Additionally, intracranial catheters artificially traverse the brain and drain the ventricle rather than the subarachnoid space. We report a 3D-printed microelectromechanical system-based implantable valve to improve HCP treatment. This device provides an alternative approach targeting restoration of near-natural CSF dynamics by artificial arachnoid granulations (AGs), natural components for CSF drainage in the brain. The valve, made of hydrogel, aims to regulate the CSF flow between the subarachnoid space and the superior sagittal sinus, in essence, substituting for the obstructed arachnoid granulations. The valve, operating in a fully passive manner, utilizes the hydrogel swelling feature to create nonzero cracking pressure, P_T ≈ 47.4 ± 6.8 mmH₂O, as well as minimize reverse flow leakage, Q_O ≈ 0.7 μL/min on benchtop experiments. The additional measurements performed in realistic experimental setups using a fixed sheep brain also deliver comparable results, P_T ≈ 113.0 ± 9.8 mmH₂O and Q_O ≈ 3.7 μL/min. In automated loop functional tests, the valve maintains functionality for a maximum of 1536 cycles with the P_T variance of 44.5 mmH₂O < P_T < 61.1 mmH₂O and negligible average reverse flow leakage rates of ∼0.3 μL/min.