Stretching DNA in nanocapillaries fabricated through coarse (>1μm) lithography

来源 :第八届全国微全分析系统学术会议、第三届全国微纳尺度生物分离分析学术会议暨第五届国际微化学与微系统学术会议 | 被引量 : 0次 | 上传用户:maailin
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  We demonstrate here a new method of fabricating in-plane cylindrical glass nanocapillaries (<100 nm) that does not require advanced patterning techniques (e.g.e-beam or nanoimprint lithography) but the standard photolithography with coarse features (>1 μm).Our method takes advantage of thermal reflow of glass on microstructured silicon and yields self-enclosed optically transparent and highly regular nanocapillaries over large areas.As conceptually described in fig.1,a triangular slender void trapped within a rectangular silicon trench due to non-conformal deposition of glass film can be transformed into a fine cylindrical nanocapillary of a desired size with the precise control of reflow temperature and duration.In the fabrication,rectangular trenches (1.5-3 μm wide,2.5 μm deep) were patterned on (100)-oriented silicon wafers (P-type,100 mm in diameter) through a single-step lithography and deep reactive ion etching.Subsequently,a layer of phosphorus silicate glass (5 μm thick) was deposited through a low-pressure chemical vapor deposition process.The thermal reflow was conducted either in a diffusion furnace (1000 °C) or in a rapid thermal processor (950 °C),both under atmosphere pressure.Fig.2a shows SEM cross-sections of slender voids trapped within a glass filling inside 2.5 μm wide trenches before and after thermal anneal that led to nanocapillaries with consistent size.Numerical simulations verifying this evolution can be found in our recent work [1].Diameters of nanocapillaries formed in different aspect ratio trenches are presented in a plot of anneal time (Fig.2b).The utility of the fabricated nanocapillaries was tested on the stretching of λ-phage DNA (Fig.3).As shown,in the capillaries having a relatively large diameter (400 nm),the molecules preserve their recoiled shape (Fig.3a),whereas those confined in smaller capillaries (200 nm) can be found stretched to length ~8.7 μm (Fig.3b).Further confinement of DNA can be observed in 50 nm capillaries with length ~14.1 μm (Fig.3c),which is in agreement with previous studies [2].In conclusion,the nanocapillaries fabricated by this cost-effective method offer great value for chip-based nanofluidic devices in various biomedical applications.
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