Microfluidic devices and methods for manufacturing microfluidic devices

Abstract

A method for manufacturing a microfluidic device includes depositing a bonding layer on a surface of a second glass layer of a glass substrate having a first glass layer and the second glass layer fused to the first glass layer, such that a masked region of the surface is covered by the bonding layer, and an exposed region of the surface is uncovered by the bonding layer; removing a portion of the second glass layer corresponding to the exposed region of the surface to form a flow channel in the glass substrate; and bonding a cover to the glass substrate with the bonding layer.

What is claimed is: 
     
         1 . A method for manufacturing a microfluidic device, the method comprising:
 depositing a bonding layer on a surface of a second glass-based layer of a glass-based substrate comprising a first glass-based layer and the second glass-based layer fused to the first glass-based layer, whereby a masked region of the surface of the second glass-based layer is covered by the bonding layer and an exposed region of the surface of the second glass-based layer is uncovered by the bonding layer;   removing a portion of the second glass-based layer corresponding to the exposed region of the surface to form a flow channel in the glass-based substrate, wherein the removing comprises exposing the exposed region of the surface of the second glass-based layer to an acid- and surfactant-containing etchant; and   bonding a cover to the bonding layer and the second glass-based layer, the cover at least partially covering the flow channel,   wherein a floor of the flow channel has an average surface flatness of at most about 100 nm/mm, as measured in a longitudinal direction at a central portion of a flow channel of a test sample with a laser interferometer and calculated from flatness data obtained from at least three respective flow channels of at least three separately formed test samples, each test sample being materially the same as the microfluidic device,   wherein the first glass-based layer defines the floor of the flow channel, the second glass-based layer defines sidewalls of the flow channel and the cover defines a ceiling of the flow channel,   wherein the second glass-based layer comprises an etch rate in the etchant that is higher than an etch rate of the first glass-based layer in the etchant, and   further wherein the first glass-based layer has a composition with more SiO 2  than the SiO 2  in the composition of the second glass-based layer.   
     
     
         2 . The method of  claim 1 , wherein the second glass-based layer has a composition comprising SiO 2  from 45 to 60 mol %, Al 2 O 3  from 8 to 19 mol %, B 2 O 3  from 5 to 23 mol %, and Na 2 O from 3 to 21 mol %. 
     
     
         3 . The method of  claim 1 , wherein the bonding layer serves as an etch mask to prevent contacting the masked region of the surface of the second glass-based layer with the etchant during the exposing of the removing step. 
     
     
         4 . The method of  claim 1 , wherein the first glass-based layer serves as an etch stop to control a depth of the flow channel during the exposing of the removing step. 
     
     
         5 . The method of  claim 1 , wherein the bonding the cover to the bonding layer and the second glass-based layer comprises:
 positioning the cover on the bonding layer; and   irradiating the bonding layer with electromagnetic radiation sufficient to diffuse at least a portion of the bonding layer into the cover and the second glass-based layer, thereby bonding the cover to the second glass-based layer.   
     
     
         6 . The method of  claim 1 , wherein the floor of the flow channel has a surface flatness variance of at most about 3 μm along a length of the flow channel, as measured at a central portion of the flow channel. 
     
     
         7 . The method of  claim 1 , wherein the floor of the flow channel has a surface roughness (Ra) of at most about 10 nm, as measured according to ISO 25178, Geometric Product Specifications, with a laser interferometer. 
     
     
         8 . A method for manufacturing a microfluidic device, the method comprising:
 depositing a bonding layer on a surface of a second glass-based layer of a glass-based substrate comprising a first glass-based layer and the second glass-based layer fused to the first glass-based layer, whereby a masked region of the surface of the second glass-based layer is covered by the bonding layer and an exposed region of the surface of the second glass-based layer is uncovered by the bonding layer;   removing a portion of the second glass-based layer corresponding to the exposed region of the surface to form a flow channel in the glass-based substrate, wherein the removing comprises exposing the exposed region of the surface of the second glass-based layer to an acid- and surfactant-containing etchant; and   bonding a cover to the bonding layer and the second glass-based layer, the cover at least partially covering the flow channel,   wherein a floor of the flow channel has an average surface flatness of at most about 100 nm/mm, as measured in a longitudinal direction at a central portion of a flow channel of a test sample with a laser interferometer and calculated from flatness data obtained from at least three respective flow channels of at least three separately formed test samples, each test sample being materially the same as the microfluidic device,   wherein the first glass-based layer defines the floor of the flow channel, the second glass-based layer defines sidewalls of the flow channel and the cover defines a ceiling of the flow channel,   wherein the second glass-based layer comprises an etch rate in the etchant that is higher than an etch rate of the first glass-based layer in the etchant, and   further wherein the first glass-based layer comprises a boro-aluminosilicate glass composition.   
     
     
         9 . The method of  claim 8 , wherein the second glass-based layer has a composition comprising SiO 2  from 45 to 60 mol %, Al 2 O 3  from 8 to 19 mol %, B 2 O 3  from 5 to 23 mol %, and Na 2 O from 3 to 21 mol %. 
     
     
         10 . The method of  claim 8 , wherein the bonding layer serves as an etch mask to prevent contacting the masked region of the surface of the second glass-based layer with the etchant during the exposing of the removing step. 
     
     
         11 . The method of  claim 8 , wherein the first glass-based layer serves as an etch stop to control a depth of the flow channel during the exposing of the removing step. 
     
     
         12 . The method of  claim 8 , wherein the bonding the cover to the bonding layer and the second glass-based layer comprises:
 positioning the cover on the bonding layer; and   irradiating the bonding layer with electromagnetic radiation sufficient to diffuse at least a portion of the bonding layer into the cover and the second glass-based layer, thereby bonding the cover to the second glass-based layer.   
     
     
         13 . The method of  claim 8 , wherein the floor of the flow channel has a surface flatness variance of at most about 3 μm along a length of the flow channel, as measured at a central portion of the flow channel. 
     
     
         14 . The method of  claim 8 , wherein the floor of the flow channel has a surface roughness (Ra) of at most about 10 nm, as measured according to ISO 25178, Geometric Product Specifications, with a laser interferometer. 
     
     
         15 . A method for manufacturing a microfluidic device, the method comprising:
 depositing a bonding layer on a surface of a second glass-based layer of a glass-based substrate comprising a first glass-based layer and the second glass-based layer fused to the first glass-based layer, whereby a masked region of the surface of the second glass-based layer is covered by the bonding layer and an exposed region of the surface of the second glass-based layer is uncovered by the bonding layer;   removing a portion of the second glass-based layer corresponding to the exposed region of the surface to form a flow channel in the glass-based substrate, wherein the removing comprises exposing the exposed region of the surface of the second glass-based layer to an acid- and surfactant-containing etchant; and   bonding a cover to the bonding layer and the second glass-based layer, the cover at least partially covering the flow channel,   wherein a floor of the flow channel has an average surface flatness of at most about 100 nm/mm, as measured and averaged in a longitudinal direction (Y-direction) at a central portion of the flow channel,   wherein the floor of the flow channel has an average surface flatness of at most about 30 nm/mm, as measured and averaged in a lateral direction (X-direction) at a central portion of the flow channel,   wherein the first glass-based layer defines the floor of the flow channel, the second glass-based layer defines sidewalls of the flow channel and the cover defines a ceiling of the flow channel,   wherein the second glass-based layer comprises an etch rate in the etchant that is higher than an etch rate of the first glass-based layer in the etchant, and   further wherein the first glass-based layer comprises a boro-aluminosilicate glass composition.   
     
     
         16 . The method of  claim 15 , wherein the second glass-based layer has a composition comprising SiO 2  from 45 to 60 mol %, Al 2 O 3  from 8 to 19 mol %, B 2 O 3  from 5 to 23 mol %, and Na 2 O from 3 to 21 mol %. 
     
     
         17 . The method of  claim 15 , wherein the bonding layer serves as an etch mask to prevent contacting the masked region of the surface of the second glass-based layer with the etchant during the exposing of the removing step. 
     
     
         18 . The method of  claim 15 , wherein the first glass-based layer serves as an etch stop to control a depth of the flow channel during the exposing of the removing step. 
     
     
         19 . The method of  claim 15 , wherein the bonding the cover to the bonding layer and the second glass-based layer comprises:
 positioning the cover on the bonding layer; and   irradiating the bonding layer with electromagnetic radiation sufficient to diffuse at least a portion of the bonding layer into the cover and the second glass-based layer, thereby bonding the cover to the second glass-based layer.   
     
     
         20 . The method of  claim 15 , wherein the floor of the flow channel has a surface flatness variance of at most about 3 μm along a length of the flow channel, as measured at a central portion of the flow channel.