Microfluidic Liquid Flow Control: Hydrophilic Treatments and Stop Valves

Need more control over sample flows in your microfluidic chips? Enplas offers non-chemical based solutions to help you achieve better microfluidic sample control.

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Methods

Enplas offers two methods of achieving high levels of control over sample flows: hydrophilic treatments and stop valves.

Hydrophilic Treatments

Enplas offers non-chemical treatments to increase hydrophilicity (i.e., the amount of water attraction) on the surfaces of molded microfluidic parts, resulting in smoother flow without bubbles. This treatment nullifies the material’s contact angle, and prevents customers from investing time and resources into developing new microchannels meant for plastics.

Additionally, Enplas’s hydrophilic treatment processes eliminate the chances of contamination by using plasma rather than chemicals on chips laminated in a clean room. And because no chemical solutions are used, there are no chemical residues to cause variations in channel dimension.

Hydrophilic treatments are also an optimal solution for those who have created a microchannel design using glass or PDMS and would like to scale up using resin, but cannot afford to accept a different contact angle.

In this method of flow control, our treated devices can fill mediums through capillary action without the use of pumps or vacuums.

Stop Valves

Sample flows can be controlled by adding a “stop valve,” or a small notch, that impedes a liquid’s flow through a microchannel.

This solution is optimal for customers that require liquids to stop flowing at a specific location within a channel. The liquid will stop moving at the notch as the surface tension of the liquid prevents it from passing until external force is applied.

In this method of flow control, fluid can be stopped in channels without any external controllers, resulting in a simplified device.

Application Examples

AUTOMATIC FILLING	BUBBLE PREVENTION	ELECTROPHORESIS
Hydrophilization allows filling of media into devices without the use of pumps or vacuums through capillary action.	High wettability suppresses the formation of bubbles.	Reagent can be filled without sample loss for SSCP analysis.

Data

Fig. A

Fig. B

Fig. C

Fig. A: Steady flow speed over one year equals no loss of hydrophilicity. Even if a liquid is passed through our treated channels consistently for a year, the hydrophilic surface will not decay. Fig. B and C: Manipulation of the notch size provides a reliable interrupt.

Specifications

HYDROPHILIC TREATMENT
Treatable Material	COP, COC, PMMA
Contact Angle	COP, COC : 95˚ -> 45˚ PMMA : 70˚ -> 60˚
Processable Channel	Theoretically, no limit. Preferred length: more than 30 mm Aspect ratio: 1
Max. Processing Cap.	4,000 pcs/month

STOP VALVE
Liquid Limitations	Contact angle must be >50˚ (e.g., PMMA vs. PBS 0.05% tween [55.7˚])

The Enplas Advantage

Enplas customers receive microfluidic products that consistently reach or exceed expected levels of quality and complexity—even at mass production volumes of 200k+ per month.

Enplas is a worldwide provider of microfluidic solutions. We are your partner for the design, development, and mass production of high-quality, high-performance microfluidic chips.

To learn more about Enplas’s microfluidic liquid flow control solutions, contact us today.