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Figure 7. Effect of HF (40%) etching time on (a) depth and (b) roughness; and (c) the effect of cream etching time on the roughness of a glass substrate (2 X 4 cm’) at room temperature.

Figure 7 Effect of HF (40%) etching time on (a) depth and (b) roughness; and (c) the effect of cream etching time on the roughness of a glass substrate (2 X 4 cm’) at room temperature.

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3 Mahsa Shirazi, Mohsen Masihi,* Hassan Mahani,* and Yousef Tamsilian’
3 Mahsa Shirazi, Mohsen Masihi,* Hassan Mahani,* and Yousef Tamsilian’
Figure 1. Schematic diagram of different fabrication methods of glass micromodels.
Figure 1. Schematic diagram of different fabrication methods of glass micromodels.
Table 1. Chemical Composition of the Soda—Lime-Silica Glass Plate 153 respectively. A commercial glass etching cream (a mixture of bifluoride 154 salt (sodium bifluoride (NaHF,) or ammonium bifluoride (NH,HF,)), 185 thickener (polysaccharides, hectorite clays, and polyurethanes), organic 186 solvents (such as dipropylene glycol methyl ether acetate), and water) 187 was purchased from Armour Products. Shipley $1813 positive 158 photoresist, provided by MicroChem, was used in the photolithography 189 method. Hydrofluoric acid (HF) 40 wt % and hydrochloric acid (HCI) 160 15 wt % were both purchased from Merck (Germany). 161 2.2. Methods. 2.2.7. Roughness Creation. To create different 162 degrees of roughness on the glass substrates, four common methods
Table 1. Chemical Composition of the Soda—Lime-Silica Glass Plate 153 respectively. A commercial glass etching cream (a mixture of bifluoride 154 salt (sodium bifluoride (NaHF,) or ammonium bifluoride (NH,HF,)), 185 thickener (polysaccharides, hectorite clays, and polyurethanes), organic 186 solvents (such as dipropylene glycol methyl ether acetate), and water) 187 was purchased from Armour Products. Shipley $1813 positive 158 photoresist, provided by MicroChem, was used in the photolithography 189 method. Hydrofluoric acid (HF) 40 wt % and hydrochloric acid (HCI) 160 15 wt % were both purchased from Merck (Germany). 161 2.2. Methods. 2.2.7. Roughness Creation. To create different 162 degrees of roughness on the glass substrates, four common methods
Table 2. Automatic Program for Preparing Glass Micromodels in an Electrical Furnace 263 264 265 266 267 268 269 270 271 272 273 methods). The depth was then calculated from the difference between the height of the flat and rough surface using Gwyddion 2.60 software with the procedure shown in Figure S2. For this purpose, several vertical lines with the same distance were first drawn on the two-dimensional profile of the sample’s depth (see the left image in Figure $2) to extract associated vertical scan line profiles from the image, putting them separately on a graph (see the right image in Figure $2). The depth was then measured from the distance between two horizontal lines passing through the minimum and maximum values of the profile height. 2.2.3.4. Atomic Force Microscopy (AFM). The non-contact mode of atomic force nulgveseopy (AFM) (Veeco aro ERDBES CPs Re- 7X +r
Table 2. Automatic Program for Preparing Glass Micromodels in an Electrical Furnace 263 264 265 266 267 268 269 270 271 272 273 methods). The depth was then calculated from the difference between the height of the flat and rough surface using Gwyddion 2.60 software with the procedure shown in Figure S2. For this purpose, several vertical lines with the same distance were first drawn on the two-dimensional profile of the sample’s depth (see the left image in Figure $2) to extract associated vertical scan line profiles from the image, putting them separately on a graph (see the right image in Figure $2). The depth was then measured from the distance between two horizontal lines passing through the minimum and maximum values of the profile height. 2.2.3.4. Atomic Force Microscopy (AFM). The non-contact mode of atomic force nulgveseopy (AFM) (Veeco aro ERDBES CPs Re- 7X +r
Figure 2. FESEM images of (a) plain glass substrate and glass substrates etched by (b, f) laser, (c, g) etching cream (60 min), (d, h) laser + etching cream (60 min), and (e, i) HF (30 min), before (i.e. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 2. FESEM images of (a) plain glass substrate and glass substrates etched by (b, f) laser, (c, g) etching cream (60 min), (d, h) laser + etching cream (60 min), and (e, i) HF (30 min), before (i.e. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 3. Three-dimensional profiles of roughness for (a, e) laser, (b) etching cream (60 min), (c, f) laser + etching cream (60 min), and (d, g) HF ( min) before (i.e. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 3. Three-dimensional profiles of roughness for (a, e) laser, (b) etching cream (60 min), (c, f) laser + etching cream (60 min), and (d, g) HF ( min) before (i.e. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 4. Effect of remaining glass shards on topography and roughness of laser-engraved subsurface. Dashed circles represented the area from which the roughness profiles were obtained.
Figure 4. Effect of remaining glass shards on topography and roughness of laser-engraved subsurface. Dashed circles represented the area from which the roughness profiles were obtained.
Figure 5. Three-dimensional profiles of depth for (a, d) laser, (b, e) laser + etching cream (60 min), (c, f) HF (30 min) before (ie. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 5. Three-dimensional profiles of depth for (a, d) laser, (b, e) laser + etching cream (60 min), (c, f) HF (30 min) before (ie. at room temperature) and after placing in the furnace (up to 670 °C).
Figure 6. Example of an inappropriate temperature program for furnace: left panel: the prepared glass substrate and right panel: undesirable effect on the glass substrate.
Figure 6. Example of an inappropriate temperature program for furnace: left panel: the prepared glass substrate and right panel: undesirable effect on the glass substrate.
Table 4. Effect of the HF Etching Time on Roughness Variance/Distribution® (NE), southwest (SW), and southeast (SE), could also be a ss: qualitative indicator of roughness distribution. A high variance ss¢ shows a heterogeneous distribution, while a low variance ss exhibits the homogeneity of roughness distribution. The results ss show that the variance of roughness distribution during the early sss times (up to 15 min) is higher than that of the late times, so consistent with the obtained results in Figure 7b, where an s6 approximately constant trend was observed in the surface s¢; roughness after the etching time of 15 min, attributed to the se: different rates of the HF reaction with different parts of the glass s«- substrate. 56: OS A Pk eek dhe LIE Bice wan cxetblx« Solmea Ciechlewtirceet TTT! ec $04 S05 506 507 508 $09 $10 $ll $12 $13 $14 $18 $16 $17 $18 $19 $20 $21 $22 $23 $24 $25 $26 $27 $28 $29 $30 $31 $32 $33 $34 $35 536 $37 $38 $39 difference between the roughness of 30 and 60 min exposure times, which are approximately equal to that of 5 min exposure time. This might be attributed to the nature of this method, as the rate of the HF reaction with different parts of the glass substrate strongly depends on the chemical composition of that section. At early times, some parts might react earlier creating a valley while the unreacted parts remain unchanged, emerging as a hillock. By increasing time up to 15 min, the number of reacted points on the surface increases, leading to the generation of more valleys and hillocks, and consequently, a higher roughness. As time goes on, the unchanged parts (as hillocks) are corroded by HF. Therefore, a decreasing trend is observed in the surface roughness due to the smoothening of the hillock heights. Considering the roughness value as the ratio of the hillock height to the valley depth, it seems that the surface roughness value was a function of the smoothening and deepening rate of the hillock height and valley depth. If the rate of hillock height smoothing was higher than that of the valley depth deepening, the roughness decreased with time, being obvious during the time interval between 15 and 30 min. However, when there is a balance between the two mentioned rates, the roughness value remains unchanged with time, clearly in the time interval between 30 and 60 min. The reported trends of glass surface roughness by HF etching vs time are different in the literature. Iliescu et al. observed an increasing trend in the roughness of the soda—lime glass surface by HF (49%) within an etching time of 40 min.** Papa et al. showed an increasing trend up to 10 min by HE (38%), followed by a constant trend upto 20 min.°* Cheng et al. reported a periodic trend of increasing—decreasing— increasing in the surface roughness of fused silica etched by a mixture of 5% HF and 10% NH,F, over 80 min.*° Koga et al. observed a reduction in the surface roughness in the first 15 min of etching and a slow increment 20 min when using HF (5%) surface.°° Therefore, the tren etching time is not specific and such as surface composition, time. Despite a significant effe in the etching times greater than for etching the soda—lime glass d of roughness variation with depends on several parameters HF concentration, and etching ct of HF etching time on both roughness and depth, no significant trend was observed for the cream etc hing time in Figure 7c; although, there was a reducing trend in the error bar values (obtained from six different points in the same sample), indicating that the time of 60 min was more suitable for ensuring the accuracy of the results. To ana times of lyze roughness variation at the end of different etching HF, the quantitative values of roughness variance for exposure times of 5, 10, 15, 20, 30, and 60 min are given in Table
Table 4. Effect of the HF Etching Time on Roughness Variance/Distribution® (NE), southwest (SW), and southeast (SE), could also be a ss: qualitative indicator of roughness distribution. A high variance ss¢ shows a heterogeneous distribution, while a low variance ss exhibits the homogeneity of roughness distribution. The results ss show that the variance of roughness distribution during the early sss times (up to 15 min) is higher than that of the late times, so consistent with the obtained results in Figure 7b, where an s6 approximately constant trend was observed in the surface s¢; roughness after the etching time of 15 min, attributed to the se: different rates of the HF reaction with different parts of the glass s«- substrate. 56: OS A Pk eek dhe LIE Bice wan cxetblx« Solmea Ciechlewtirceet TTT! ec $04 S05 506 507 508 $09 $10 $ll $12 $13 $14 $18 $16 $17 $18 $19 $20 $21 $22 $23 $24 $25 $26 $27 $28 $29 $30 $31 $32 $33 $34 $35 536 $37 $38 $39 difference between the roughness of 30 and 60 min exposure times, which are approximately equal to that of 5 min exposure time. This might be attributed to the nature of this method, as the rate of the HF reaction with different parts of the glass substrate strongly depends on the chemical composition of that section. At early times, some parts might react earlier creating a valley while the unreacted parts remain unchanged, emerging as a hillock. By increasing time up to 15 min, the number of reacted points on the surface increases, leading to the generation of more valleys and hillocks, and consequently, a higher roughness. As time goes on, the unchanged parts (as hillocks) are corroded by HF. Therefore, a decreasing trend is observed in the surface roughness due to the smoothening of the hillock heights. Considering the roughness value as the ratio of the hillock height to the valley depth, it seems that the surface roughness value was a function of the smoothening and deepening rate of the hillock height and valley depth. If the rate of hillock height smoothing was higher than that of the valley depth deepening, the roughness decreased with time, being obvious during the time interval between 15 and 30 min. However, when there is a balance between the two mentioned rates, the roughness value remains unchanged with time, clearly in the time interval between 30 and 60 min. The reported trends of glass surface roughness by HF etching vs time are different in the literature. Iliescu et al. observed an increasing trend in the roughness of the soda—lime glass surface by HF (49%) within an etching time of 40 min.** Papa et al. showed an increasing trend up to 10 min by HE (38%), followed by a constant trend upto 20 min.°* Cheng et al. reported a periodic trend of increasing—decreasing— increasing in the surface roughness of fused silica etched by a mixture of 5% HF and 10% NH,F, over 80 min.*° Koga et al. observed a reduction in the surface roughness in the first 15 min of etching and a slow increment 20 min when using HF (5%) surface.°° Therefore, the tren etching time is not specific and such as surface composition, time. Despite a significant effe in the etching times greater than for etching the soda—lime glass d of roughness variation with depends on several parameters HF concentration, and etching ct of HF etching time on both roughness and depth, no significant trend was observed for the cream etc hing time in Figure 7c; although, there was a reducing trend in the error bar values (obtained from six different points in the same sample), indicating that the time of 60 min was more suitable for ensuring the accuracy of the results. To ana times of lyze roughness variation at the end of different etching HF, the quantitative values of roughness variance for exposure times of 5, 10, 15, 20, 30, and 60 min are given in Table
Figure 8. FESEM images of the HF chemical reaction with the glass surface after an exposure time of 15 min.
Figure 8. FESEM images of the HF chemical reaction with the glass surface after an exposure time of 15 min.
Figure 9. Effect of isotropic etching of HF in three-dimensional profiles of (a) roughness and (c) depth of wide fracture (aperture size of 1.7 cm); (b) roughness and (d) depth of narrow fracture (aperture size of 0.2 cm).
Figure 9. Effect of isotropic etching of HF in three-dimensional profiles of (a) roughness and (c) depth of wide fracture (aperture size of 1.7 cm); (b) roughness and (d) depth of narrow fracture (aperture size of 0.2 cm).
Table 5. Technical Comparison of Different Etching Methods 591 penetration of acid in the grain surface, as well as the incomplete 592 formation of grain or deviated fractures from the straight line, 593 attributing to the low resistance of photoresist while exposing to 594 acid or acid penetration in the boundaries such as grains or sos fracture wall boundaries. Pa gi a ae
Table 5. Technical Comparison of Different Etching Methods 591 penetration of acid in the grain surface, as well as the incomplete 592 formation of grain or deviated fractures from the straight line, 593 attributing to the low resistance of photoresist while exposing to 594 acid or acid penetration in the boundaries such as grains or sos fracture wall boundaries. Pa gi a ae
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