Polymeric check valve with an elevated pedestal for precise cracking pressure in a glaucoma drainage device

• Published in: Biomedical microdevices Vol. 18; no. 1; pp. 20 - 8
• Main Authors: Park, Chang-Ju, Yang, Dong-Seong, Cha, Jung-Joon, Lee, Jong-Hyun
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2016; Springer Nature B.V
• Subjects: Biological and Medical Physics; Biomedical engineering; Biomedical Engineering and Bioengineering; Biophysics; Channels; Devices; Drainage; Drainage facilities; Engineering; Engineering Fluid Dynamics; Feedback; Glaucoma; Glaucoma Drainage Implants; Humans; Intraocular Pressure; Membranes; Nanotechnology; Polymers; Prosthesis Design; Valves; Glaucoma drainage device; Aqueous humor; Parylene C film; Feedback channel; Micro check valve; Pre-stress
• ISSN: 1387-2176; 1572-8781
• DOI: 10.1007/s10544-016-0048-0

This paper presents the design, fabrication, and characterization of a polymeric micro check valve for a glaucoma drainage device (GDD) featuring the precise regulation of intraocular pressure (IOP) and effective aqueous humor turnover (AHT). The pedestal, slightly elevated by selective coating of a parylene C film, induces pre-stress in the thin valve membrane, which enhances the predictability of the cracking pressure of the GDD. The proposed GDD comprises a cannula and a normally closed polymeric micro check valve, which are made of PDMS, a biocompatible polymer, with three layers: top (cover), intermediate (thin valve membrane), and bottom (base plate). A feedback channel, located between the top and intermediate layers, prevents reverse flow by feeding the pressure of the outlet channel back to the thin valve membrane. To achieve a precise cracking pressure and sufficient drainage of humor for humans, the thicknesses of the valve membrane and parylene C film are designed to be 58 μm and 1 μm, respectively, which are confirmed using a COMSOL simulation. The experimental results show that the cracking pressure of the fabricated GDD lies within the range of normal IOP (1.33–2.67 kPa). The forward flow rate (drainage rate), 4.3 ± 0.9 μL/min at 2.5 kPa, is adequate to accommodate the rate of AHT in a normal human eye (2.4 ± 0.6 μL/min). The reverse flow was not observed when a hydrostatic pressure of up to 4 kPa was applied to the outlet and the feedback channel.