Research Papers

The Hermeticity of Compression Seals in Microchannel Hemodialyzers

[+] Author and Article Information
Brian K. Paul

Oregon State University,
School of Mechanical, Industrial, and
Manufacturing Engineering,
Corvallis, OR 97331-6001
e-mail: Brian.paul@oregonstate.edu

Dustin K. Ward

Oregon State University,
School of Mechanical, Industrial, and
Manufacturing Engineering,
Corvallis, OR 97331-6001
e-mail: warddu@onid.orst.edu

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received April 13, 2014; final manuscript received May 20, 2014; published online July 8, 2014. Assoc. Editor: Chengying Xu.

J. Micro Nano-Manuf 2(3), 031006 (Jul 08, 2014) (9 pages) Paper No: JMNM-14-1026; doi: 10.1115/1.4027778 History: Received April 13, 2014; Revised May 20, 2014

Most end stage renal disease patients receive kidney hemodialysis three to four times per week at central medical facilities. At-home kidney dialysis increases the convenience and frequency of hemodialysis treatments which has been shown to produce better patient outcomes. One limiting factor in realizing home hemodialysis treatments is the cost of the hemodialyzer. Microchannel hemodialyzers produced using compression sealing techniques show promise for reducing the size and cost of hemodialyzers. Challenges include the use of a 25 μm thick elastoviscoplastic (EVP) mass transfer membrane for gasketing. This paper provides a framework for understanding the hermeticity of these compression seals. The mechanical properties of a Gambro AN69ST membrane are determined and used to establish limits on the dimensional tolerances of the polycarbonate (PC) laminae containing sealing bosses used to seal the hemodialyzer. The resulting methods are applied to the fabrication of a hemodialysis device showing constraints on the scaling of this method to larger device sizes. The resulting hemodialysis device is used to perform urea mass transfer experiments without leakage.

Copyright © 2014 by ASME
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Grahic Jump Location
Fig. 1

Lamina design for microchannel hemodialyzer: four outer registration holes; two inner holes at the end of the pin-array header for fluidic interconnect; and a sealing boss around the perimeter of the header

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Fig. 2

(Top) Rendering of clamp used to clamp the hemodialysis device stack showing top window for optical access. Load cell wires shown extending. (Bottom) Cross section of single layer microchannel hemodialysis assembly (not to scale). Foam insert and PDMS layers added to distribute pressure.

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Fig. 3

Schematic of boss–membrane interaction after compressive strain engagement due to load. Clamping Force (Fc) is distributed over the lamina through the use of foam inserts within the clamping fixture.

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Fig. 4

Stress versus strain plot of AN69ST membrane that was loaded and held at 50% compressive strain for 12 h three times in sequentially

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Fig. 5

Isochronous curves of the characteristic relaxation of the membrane at various strains

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Fig. 6

Retained compressive stress for 0.2, 0.5, and 0.8 compressive strains

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Fig. 7

Log–log plot of compressive strain over time showing the characteristic creep of the membrane at a constant stress 0.4 MPa. The knee near 0.03 h is the end of the loading time.

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Fig. 8

CDE is defined based on the limits of the retained compressive strain within the membrane

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Fig. 9

Schematic of hermeticity test article

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Fig. 10

Schematic of the experimental setup used for hermeticity experiments

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Fig. 11

Typical image obtained with the ZeScope for CPS depth measurements

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Fig. 12

Typical constant stress test used to provide characteristic elastic strain recovery percent for a typical loading and 10 min hold of a membrane stack

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Fig. 13

Elastic strain recovery percent graph as a function of plastic strain after 10 min of compression

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Fig. 14

Measured CPS10 (dashed crooked), calculated CDD10 (solid crooked) and average CDD10 (dashed straight) at load parameters of 2.5, 5, 10, and 15 N/cm from top to bottom, respectively, for the first set of dry run samples. The CDE (solid straight) is overlaid to show whether hermeticity conditions are met. Out-of-hermeticity conditions are circled.

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Fig. 15

Same set of graphs for the second set of dry run samples. Colors have same meaning as in Fig. 14 (see online version).

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Fig. 16

Measured CPS10 (dashed crooked), calculated CDD10 (solid crooked) and average CDD10 (dashed straight) after mitigating the effects of dimensional variation. The CDE (solid straight) is overlaid to show that hermeticity conditions were met.




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