Methods for establishing hydrophilic and hydrophobic areas on a surface of a substrate or film and associated microfluidic devices
Inventors
VARGAS, Matheus Jose Teixeira • Simpson, Miriam Cather • Williams, David Edward
Assignees
Publication Number
US-11618105-B2
Publication Date
2023-04-04
Expiration Date
2041-11-13
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Abstract
Embodiments of the present disclosure are directed to methods, systems and devices, for precise and reduced spot-size capabilities using a laser to alter surfaces without chemical treatment, chemical waste, or chemical residues is provided for microfluidic systems (e.g., lab-on-a-disk, for example). In some embodiments, hydrophobic and super-hydrophilic areas can be created on surfaces in the same material at different areas and positions merely by using different laser settings (e.g., spot size, wavelength, spacing, and/or pulse duration). Accordingly, capillary forces that are a recurrent issue in a microfluidic devices (e.g., a centrifugal microfluidic disk) can be controlled for practical applications, including, for example when users handle the disks and insert a sample, the moment the substrate/device (e.g., disk) is placed in a system (e.g., a centrifugal system), capillary forces can take place and move the fluids, which becomes a problem for sequential bioassays taking place in substrate/device (e.g., disk). Thus, in some embodiments, the systems, devices and methods increase fluid control in microfluidic devices.
Core Innovation
The invention provides methods, systems, and devices for controlling fluid flow in microfluidic devices by precisely altering the wettability of a substrate or film surface using laser ablation without the need for chemical treatment, chemical waste, or residues. It enables the formation of hydrophobic and super-hydrophilic areas on the same material at different positions by using different laser parameters, such as wavelength, spot size, spacing, and pulse duration. This is accomplished by applying nanosecond UV laser pulses to produce super-hydrophilic surfaces and femtosecond IR laser pulses to create hydrophobic or super-hydrophobic surfaces.
The problem addressed by the invention relates to the difficulty of controlling fluid flow and capillary forces inside microfluidic channels as they miniaturize. Traditional methods rely on chemically modifying large surface areas or inserting materials to create valves, which is complex and less precise. Controlling capillary forces and fluid flow via flux valves in microchannels is crucial for accuracy in sequential bioassays and for managing sample insertion and processing in devices like centrifugal microfluidic disks.
Embodiments of the invention provide laser-based surface modification techniques that enable site-specific and high-precision regulation of fluid flow by establishing selective hydrophobic or super-hydrophilic micro-areas acting as valves within microfluidic channels. This modulation adjusts burst pressures and capillary forces in the channels, allowing better control of fluid movement using centrifugal forces without chemical reagents or post-processing. The invention also offers tunability of surface wettability, enabling miniaturization and precise fluid metering in microfluidic systems.
Claims Coverage
The patent includes one independent claim focused on a method for making hydrophobic and super-hydrophilic areas via laser ablation and outlines various laser parameters for achieving desired wettability on substrate surfaces.
Method for making hydrophobic and super-hydrophilic areas via laser ablation
Forming hydrophobic and super-hydrophilic areas on at least one surface of a substrate or film by machining using laser ablation via a plurality of spot pulses applying a mask or spatial light modulator, where super-hydrophilic areas are created using a nanosecond laser and hydrophobic areas are created using a femtosecond laser.
Configuration of nanosecond laser parameters for super-hydrophilic areas
Adjusting laser power based on ablation depth, tuning wavelengths within the UV range (150-400 nm), pulse durations between 1-50 ns, repetition rates between 1 Hz and 5 kHz, pulse spot sizes between 10-10,000 µm², and spatial spacing between pulses and lines within nanometer to micrometer scales to create super-hydrophilic surfaces.
Configuration of femtosecond laser parameters for hydrophobic areas
Adjusting laser power from 1 mW to 1000 mW, wavelengths between 680-1130 nm (IR range), pulse durations between 10-400 fs, repetition rates between 500 Hz and 300 kHz, pulse spot sizes between 1-2500 µm², and pulse spacing between 100 nm to 100 µm to create hydrophobic or super-hydrophobic surfaces.
Use of polycarbonate substrate or film with potential additional layers
Applying the laser ablation methods to polycarbonate (PC) substrates or films or substrates with similar properties, optionally adhered to additional layers such as polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), or pressure sensitive adhesive layers.
Application of hydrophobic and super-hydrophilic areas as microfluidic valves
Configuring the laser-fabricated hydrophobic and super-hydrophilic areas as valves within microfluidic circuits, devices, or channels to control fluid flow.
The claims collectively cover the precise laser-based fabrication method to produce controllable hydrophobic and super-hydrophilic areas on substrates, specifying detailed laser parameters and materials, and the use of these areas as functional valves in microfluidic devices.
Stated Advantages
Enables precise fluid control in microfluidic devices without the use of chemical reagents, thus avoiding chemical waste and residues.
Allows for site-specific and high-precision wettability modification with micro- or nano-scale resolution.
Facilitates the tunability of wettability properties by adjusting laser parameters, permitting customization of burst pressures and valve functions.
Supports miniaturization of microfluidic circuits by controlling capillary forces more effectively.
Simplifies manufacturing by avoiding elaborate chemical modifications and enables manufacturing on standard polymer substrates, such as polycarbonate.
Documented Applications
Use in centrifugal microfluidic disks to create hydrophobic and super-hydrophilic valves for controlling fluid flow and burst pressures within microchannels.
Application in microfluidic biosensors and lab-on-a-chip devices requiring sequential bioassays with precise fluid manipulation.
Use in open microfluidic circuits to control fluid capillary action with tailored hydrophobic or super-hydrophilic surface patterns.
Formation of microfluidic pathways and valves in layered polymer substrates for biomedical and biochemical sample processing.
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