This thesis presents a novel method and device for cell deformability monitoring based on the cell lysis rates through a filter array having gradually increased orifice length. Compared to the conventional filtration, the present method is insensitive to the cell volume deviation since the lysis rate is dependent on the ratio of cell surface area to volume. The present method also provides simple and inexpensive system by eliminating optical components.
The present cell deformability monitoring chips consist of four filters with variable orifice lengths with electrical sensing zones located before and after each filter. We design and fabricate three types of devices with 3 different orifice lengths: 2, 6.7, 11.2, 16μm for T-device, 2, 4.5, 6.7, 9μm for L-device and 9, 11.2, 13.6, 16μm for U-device. Since the tension of the cell membrane passing through the filters is proportional to the orifice length, each device types impose various tensions. Devices are fabricated by photolithography and PDMS molding process.
In the experimental study, we use normal and chemically treated erythrocytes to compare the lysis rate depending of cell deformability. The maximum differences of lysis rate between normal and chemically treated erythrocytes are measured as 21.2 3.5% in the 6.7μm long orifice of T-devices, and 16.6 4.6% in the 4.5μm long orifice of L-devices. We estimate that the orifice length range of 4~7μm effectively discriminate the deformability difference of erythrocytes. For an improved accuracy of the cell deformability measurement, we suggest a modified design preventing plugging of the erythrocytes.
In this work, we verify that the present cell deformability monitoring chips have potentials for quantifying the deformability of the cells in different physical condition.