Implantable microdevice for the treatment of hydrocephalus

Jonghyun Oh

doi:10.17918/etd-3443

We present a novel microdevice for the treatment of hydrocephalus. Hydrocephalus is a pathological condition in which excessive cerebrospinal fluid (CSF) is accumulated within the subarachnoid space of the brain due to deficient arachnoid granulations, resulting in the brain damage or death. Current treatment for hydrocephalus is to surgically implant a shunt device to drain the excessive fluid from the ventricles to peritoneal cavity or other parts of the body. This method has over 50% failure rate due to occlusions and mechanical failures of shunt components. The proposed microfabricated device can mimic the function of normalarachnoid granulations and thus can replace the deficient arachnoid granulations. The microfabricated arachnoid granulations (MAG) consist of arrays of microvalves and microneedles. The microvalves are made of a PDMS/Parylene composite layer and have a 3-D dome petal shape. Such geometry enables the microvalve to rectify fluid flow in the forward and backward direction due to pressure differentials like normal arachnoid granulation. Microvalve design was optimized using 3-D numerical simulation. The microvalves were fabricated using three main microfabrication techniques: diffuser lithography for dome-shaped SU-8 mold fabrication, thin polymer film deposition and reflow for PDMS/Parylene membrane formation, and excimer laser machining for valve opening. The pressure drop vs. flow rate characteristics of the fabricated microvalve was investigated through in-vitro flow tests using a bench-top CSF simulator. The results showed that a 10x10 microvalve array with combined opening shape is optimal for our application. The microneedle array is to surgically pierce the dura mater membrane after being assembled with the microvalve. The microneedles were fabricated using three main techniques: diffraction photolithography for tapered SU-8 needle fabrication, RIE etching for needle sharpening, and excimer laser machining for through-hole creation. Puncture tests were conducted using pig's dura mater and the microneedles coated with a Ti layer showed promising results (16 out of 100 needles pierced dura and the needles were not deformed). Blood adhesion tests were also carried out using human blood simulating the CSF dynamics and no significant platelet adhesion was observed at the microneedles. The MAG presented in this dissertation demonstrates a great potential for the treatment of hydrocephalus.

Implantable microdevice for the treatment of hydrocephalus

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Implantable microdevice for the treatment of hydrocephalus

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