研究目的
To develop easy-to-operate fabrication methods for tapered glass capillaries with controlled tip sizes for microdroplet generation applications, addressing challenges in repeatability and cost-effectiveness.
研究成果
The study demonstrates that chemical etching provides the best repeatability and control for fabricating tapered glass capillaries with desired tip sizes, making it suitable for industrial-scale mass production. The fabricated capillaries enable uniform microdroplet generation, with droplet size controllable by tip dimensions and flow rates. The methods offer improvements over traditional techniques in terms of geometry precision and application performance.
研究不足
The sanding method is labor-intensive and not suitable for mass production; chemical etching involves hazardous materials (HF) requiring strict safety measures and is not environmentally friendly; advanced pulling methods require extensive trial-and-error and are dependent on specific equipment and glass types, limiting scalability and reproducibility.
1：Experimental Design and Method Selection:
The study compares mechanical (sanding) and chemical (etching) methods for enlarging and standardizing the tip sizes of glass capillaries initially pulled using a micropipette puller. The design rationale is to achieve precise control over tip dimensions for microfluidic droplet generation.
2：Sample Selection and Data Sources:
Hollow glass capillaries with ring/square/θ shape cross-sections are used, characterized by inner diameter, outer diameter, wall thickness, and length. Samples are prepared using standard pulling programs and then modified.
3：List of Experimental Equipment and Materials:
Equipment includes micropipette puller (P-1000, Sutter Instrument), micro forger (MF-900, Narishige), force sensor (Hochoice UTP313-4), optical contact angle meter system (SDC-80), CCD camera, sandpaper (5000 and 10000 grits), etchant (hydrofluoric acid, HF, and nitric acid, HNO3), deionized water, petri dish, clamping manipulator, and various glass capillaries from suppliers like Jiaoleji Co. Lt. and Ruisheng Borosilicate Company.
4：Experimental Procedures and Operational Workflow:
Capillaries are first pulled to sharp tips (1-3μm) using a micropipette puller. For mechanical sanding, tips are sanded with abrasive paper; force and distance are measured. For chemical etching, tips are immersed in HF etchant, with concentration and time varied; the process is monitored optically. Microforging is optionally used for smoothing.
5：Data Analysis Methods:
Tip sizes are measured microscopically, and data are analyzed using linear fitting algorithms to establish relationships between parameters (e.g., heating temperature, pulling velocity, sanding distance, etching time) and tip size. Statistical analysis includes coefficient of variation calculations.
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micropipette puller
P-1000
Sutter Instrument
Used to pull glass capillaries to form sharp tapered tips with controlled dimensions.
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micro forger
MF-900
Narishige
Used to smoothen and forge the tip endings of glass capillaries after pulling or other processing.
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force sensor
UTP313-4
Hochoice
Used to measure the impact force during dropping and sanding processes to quantify fabrication parameters.
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optical contact angle meter system
SDC-80
Germany (specific brand not mentioned, inferred from 'Germany')
Used for real-time monitoring of the chemical etching process by capturing side views of the glass capillary.
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CCD camera
Integrated into the contact angle meter system to capture images during etching for analysis.
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sandpaper
5000 grits, 10000 grits
Eagle & AX (inferred from 'Eagle & AX10000 grits')
Used for mechanical sanding to enlarge and smoothen the tip endings of glass capillaries.
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hydrofluoric acid
AR, 40.0%
Shanghai Macklin Biochemical Co. Ltd.
Used as the primary etchant in chemical etching to modify the tip size of glass capillaries.
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nitric acid
69wt%
Used in mixture with HF for etching in some cases.
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glass capillary
ID 1mm, OD 1.5mm
Jiaoleji Co. Lt.
Basic material used for fabrication, with specific geometries for microfluidic applications.
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square glass capillary
Inner 1.5mm square, Outer 1.9mm square
Ruisheng Borosilicate Company
Used in the assembly of microfluidic devices for droplet generation.
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