In this thesis, two types of size-dependent microparticle capture and release chips have been proposed and demonstrated for high retrieval efficiency: size-dependent microparticle capture and release chip and circulating tumor cell capture and release chip.
Previous microparticle separation methods, using multiple filters with different pore sizes, require additional structures and processes to release the microparticles after they are captured in the filters. In addition, those methods often result in particle loss due to clog-ging of the fixed filters. We suggest the microparticle capture and release chips, capable of size-dependent microparticle capture and release without the particle loss by using deformable membrane ring barriers.
The size-dependent microparticle separation chip has different slit gaps formed by multiple membrane ring barriers (b1 ~ b4) concentrically spread out from the inlet, which can adjusted with a unit pressure source. The chip is able to not only capture microparticles by size, but also recover the respectively captured microparticles without microparticle clogging, by simply controlling the slit gaps produced by the deformable multiple membrane ring barriers using the unit pressure source. In the experiments, we demonstrated microparticle separa-tion and release using two different sizes of PS (Polystyrene) beads (diameter = $6.51 \pm 0.43 \mu m$ and $10.32 \pm 0.39 \mu m$) immersed in 0.5% BSA (Bovine Serum Albumin) solution at a sample flow rate of 6 ml/h. At a pressure of 80 kPa, $10.32 \mu m$ and $6.51 \mu m-diameter$ beads were captured at the ring barriers of $b_3$ and $b_4$. The capture efficiency of $10.32 \mu m$ and $6.51 \mu m-diameter$ beads at the barriers were $91.7 \pm 16.7%$ and $100.0 \pm 0.0%$, respectively. Sub-sequently, at membrane pressures of 65 kPa and 50 kPa, the $6.51 \mu m$ and $10.32 \mu m-diameter$ beads were respectively released from the outermost barrier ($b_4$). The release efficiency of $10.32 \mu m-diameter$ beads at the $b_3 barrier and $6.51 \mu m-diameter$ beads at the $b_4$ barrier were $90.9 \pm 8.1%$ and $97.1 \pm 4.0%$, respectively. We have verified that the different sizes of captured microparticles were captured and effectively released using the chip.
A circulating tumor cell (CTC) capture and release chip uses the slanted slots formed by a deformable membrane ring barrier for CTC capture and release. The chip is capable to capture the CTCs with the reduced mechanical stress and cell damage by using the slanted slots formed by the inflated membrane ring barrier. In addition, it is capable to effectively release the captured CTCs without cell clogging by deflating the deformable membrane ring barrier and opening the slots. In the experiments, we demonstrated cancer cell capture and release using two types of cancer cells (H358, LoVo) spiked in PBS solution and peripheral blood mononuclear cell (PBMC) suspension at a sample flow rate of 0.8 ml/h and a membrane pressure of 95 kPa. The average capture and release efficiency for H358 and LoVo cells spiked in PBS solution were $87.9 \pm 1.4%$, and $100.0 \pm 0.0%$, respectively. The average capture and release efficiency for H358 and LoVo spiked in PBMC suspension were $74.7 \pm 3.5%$ and $94.8 \pm 2.1%$, respectively. Finally, we have isolated and retrieved the CTCs from lung and colorectal cancer patients’ bloods. The present chip, which can form the slanted slots and open the slots using the deformable membrane ring barrier, is capable of viable CTC capture and efficient retrieval. The present chip enables the CTC researchers to continue the culture and molecular analysis of CTCs for cancer diagnosis and prognosis.
We have proposed and demonstrated two size-dependent microparticle capture and release chips using the deformable membrane ring barriers. The deformable membrane ring barriers are effective to release the captured microparticles without particle clogging. The presented chips are applicable to further research on the retrieved microparticles.