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Application of Ultraprecision Microgrooves to Dental Implant and Blood Inspection
Available online at www.sciencedirect.com
Procedia CIRP 5 (2013) 147 – 151
The First CIRP Conference on Biomanufacturing
Application of ultraprecision microgrooves to dental implant and blood inspection Tohru Ishidaa, Koji Teramotob, Keiichi Nakamotoc, Yoshimi Takeuchid,* a
Tokushima University, 2-24 Shinkura, Tokushima 770-8501, Japan Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan c Tokyo University of Agriculture and Technology, 2-24-16 Naka, Koganei 184-8588, Japan d Chubu University, 1200 Matsumoto, Kasugai 487-8501, Japan * Corresponding author. Tel.: +81-568-51-9666; fax: +81-568-51-1194. E-mail address: [email protected]. b
Abstract Ultraprecision micromachining technology is expected to be a potential tool of producing bio-related parts though it is a traditional one. The characteristic of the ultraprecision micromachining technology is the high possibility of selecting various kinds of metals and creating complicated shapes with high dimensional accuracy and surface quality. The study introduces two cases, dental implants and microchannel chips, by means of ultraprecision microgrooves as applications of ultraprecision micromachining technology. As seen from machined results, it is found that the ultraprecision microgrooving technology has the potential of producing a variety of bio-related parts as well as mechanical parts and optical elements. © 2013 2012The TheAuthors. Authors. Published by Elsevier © Published by Elsevier B.V. B.V. Selection and/or peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Bartolo Selection and/orPaulo peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Paulo Bartolo Keywords: Ultraprecision micromachining ; Microgroove ; Bio-related parts ; Dental implant ; Blood inspection
1. Introduction In these days, ultraprecision micromachining technology is playing an important role to produce precision parts and optical elements such as diffraction grating, micro Fresnel lens and so on [1]. From now on, the application of ultraprecision micromachining technology to bio fields is now expected to a great extent. Here, let us introduce two kinds of examples of ultraprecision microgrooving technology. One is the creation of microgrooves for dental implants, which are the artificial tooth roots inserted to the jawbone. Dental implants easily allow bacteria to intrude to the gingival surface, thus resulting in the dissolution of tooth bone. As a result, dental implants are easily removed. To cope with the problem, it is desirable to make microgrooves around the circumferential surface of dental implants and to block the intrusion of bacteria biologically by developing epithelium cells or
Implants
Titanium Implant
Intrusion of bacteria
Microgrooves Gingiva Teeth
Bone tissues
Bone tissues Gingiva
Jaw Bone
Fig. 1. Dental implants
fibroblasts in the direction of microgrooves, as shown in Fig. 1 [2]. As the first step, compound V-shaped microgrooves are created on a plane surface. The other application is to develop micro-rheology d ev ic e to me a su r e b lo o d f lu id i t y in ter ms o f investigating flow mechanism of blood, as illustrated in
2212-8271 © 2013 The Authors. Published by Elsevier B.V. Selection and/or peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Paulo Bartolo doi:10.1016/j.procir.2013.01.030
148
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
C
Rotational tool
Non-rotational tool Z
Workpiece
Y B X Fig. 3. Setups of ultraprecision cutting (a) Rotational tool; (b) Nonrotational tool Microscope ( 2000)
Glass plate 45
Red corpuscle
mm
8m
m
( )
ih
i
l
l
(b)
ih
i
50 μm
50 μm
50 μm
Fig. 2. Configuration of microchannel chip to inspect corpuscle flow
2. Ultraprecision machining center and machining method Figure 3 illustrates setups in cutting with the ultraprecision machining center used for the experiments. The utilized machining center is ROBONANO by FANUC Ltd., and has five axes, i.e., X, Y, and Z axis as translational axes, and B and C axis as rotational ones.
l
50 μm
Mirror surface
Mirror surface
150
2 μm 90
2 μm
1 mm
0.42 μm
Fig. 2. The device allows human blood flow to pass through microchannel array built on a chip as a model of capillary vessels due to its shape, where many microgrooves are arranged in parallel. At the same time, the blood flow through the microchannels can be visually observed, which can evaluate its fluidity. Consequently, the employment of microchannel array chips made of various metals is expected to evaluate the compatibility between blood and metals. However, a microchannel array, i.e., arrangement of a lot of microgrooves, is generally built on silicon by means of photolithographic techniques, which results in low controllability of the shape of the microgrooves. The shape and accuracy of the microgroove are extremely important to measure blood fluidity with a microchannel array chip. To solve the problem, the study aims at fabricating the microchannel array chip by ultraprecision machining.
l
Fig. 4. Difference in methods to make V-shaped microgrooves (a) Rotational tool; (b) Non-rotational tool
90
2 μm 90
0.42 μm
16
Fig. 5. Configuration of compound microgrooves
The positioning resolutions of the translational axes and the rotational axes are 1 nm and 0.00001 , respectively. The machining center is designed, based on the concept of friction-free servo structures. Namely, pneumatic air bearings are adopted for the rotational and translational axes and the other movements, thus resulting in elimination of solid friction completely [3]. As illustrated in Fig. 3, the machining center has two type cutting methods according to the employed tool, that is, rotational tool or non-rotational tool. The former is attached to a high-speed air turbine spindle mounted on C table, as shown in Fig. 3 (a). The latter is directly fixed on C table through a jig, as shown in Fig. 3(b). A workpiece is mounted on B table in both cases. Figure 4 represents the appearances in machining a V-shaped microgroove with the former and the latter, respectively. Both tools are equipped with a diamond tip, which has cutting edge of 90 in nose angle. In case of the former, the microgrooving is carried out with the tool rotating, as
149
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
Trapezoid grooving C table
Workpiece 2 μm
Diamond cutting tool
2 μm
(a) Left slope (b)
Workpiece
(c)
V-shaped grooving
Pickfeed directions 2 μm
Fig. 6. Machining method of microgrooves
illustrated in Fig. 4 (a), and in case of the latter, it is done with the tool not rotating, as illustrated in Fig. 4(b). The same V-shaped microgroove of 90 in bottom angle can be machined in both cases.
(c) Right slope
Fig. 7. Machined V-shaped microgrooves (material: 18k-gold alloy) (a) Left slope; (b) Top surface; (c) Right slope Table 1. Cutting conditions Workpiece
As illustrated in Fig. 5, compound microgrooves in the study consist of trapezoid grooves having V-shaped microgrooves. The size of V-shaped microgrooves is 2 m in pitch and 90 at groove angle. Every trapezoid groove is 150 m in pitch with the plateau length of 50 m and groove angle of 30 . Trapezoid bottom parts are required to be a mirror surface. The shape of compound microgrooves is determined from the viewpoint of fabricating a simplified model of dental implants. To carry out compound V-shaped microgrooving, a high speed air turbine spindle with a trapezoid- shaped diamond cutting tool is mounted on C table, as shown in Fig. 6. In this case, three translational axes are used: X axis for the tool feed direction, Z axis for the pitch control and Y axis for the depth of cut. After the trapezoid microgrooves are completed, the diamond cutting tool is changed to a 90 V-shaped one in order to fabricate V-shaped microgrooves on trapezoid groove surfaces. Grooving is carried out in the down-cut manner. The work material used is 18K gold alloy. 3.2. Machined result and cell cultivation experiment Figure 7(a), (b) and (c) show SEM images of machined compound V-shaped microgroove surfaces under the cutting condition listed in Table 1. From these figures, it is seen that the fine microgrooves can be fabricated on the trapezoid groove surface. The machined compound grooves have smooth surfaces and sharp edges without any burr generation. The surface
Spindle rotation
45,000 rpm
Feed speed
50 mm/min
Depth of cut
Trapezoid
V-shaped
Rough cut
10 m
1.0 m
Finish cut
1.0 m
0.5 m
Without microgrooves
3.1. . Configuration of compound V-shaped microgrooves and machining method
18k-gold alloy
With microgrooves
3. Creation of microgrooves for dental implants
Polystyrene cultivation bed
Z (PF) X
(a)
Fee d dire ctio n
Workpiece
(b) Top surface
Fig. 8. Growing cells with and without V-shaped microgrooves
roughness of the bottom part in trapezoid microgrooves was approximately 15 nmRmax, which shows the mirror surface finish. About 30hours was spent to fabricate the grooves. In case of V-shaped grooving on the trapezoid slope, there are two pickfeed directions: upward direction and downward one along the trapezoid slope. The former could achieve better machining surface, compared with the latter. In the latter, some burrs took place along the edge and groove surface. Thus, it is preferable to select the upward pickfeed direction.
150
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
Polystyrene cultivation bed
Non-rotational tool
100 μm
(a) Machining of the bank Non-rotational tool
Tool trajectory
(b) Machining of the diamond shape on one side
Fig. 9. Accumulative cells on compound microgrooves
Glass contact surface
Square-shaped microgrooves
Bank
(c) Machining of the diamond shape on the other side
10 μm
Fig. 11. Machining method of bank and square-shaped microgrooves
Shank
5 μm
Shank
100 μm
90º 15 μm 100 μm 100 μm
200 μm
19 μm Diamond
10 mm
Diamond
Diamond tip
Fig. 12. Non-rotational tool employed to machine microgrooves Fig. 10. Dimension of microchannel
A cultivation bed of polystyrene is produced from a metal mold of the machined compound V-shaped microgrooves in order to carry out cultivation experiments by use of it. Figure 8 shows an experimental result, where the epithelium cells on the pale part without microgrooves grow up in the random direction. On the other hand, cells on V-shaped microgrooves grow up along the direction of microgrooves. As shown in Fig. 9, it is also seen that cells form the accumulative layers on the bottom part of trapezoid groove. It is confirmed that cells can be controlled to the intended direction by using compound V-shaped microgrooves. 4. Creation of microchannel chip for micro-rheology device 4.1. Shape of microchannel and machining plan Figure 10 illustrates the dimensions of the designed microchannel, which consists of square-shaped microgrooves. The designed chip has the slender rectangular-prism-shaped objects on the bank. The
object is 10 m in width, 5 m in height, and 100 m in length, and has diamond-shaped edges. The objects are arranged at several intervals of 25 m, 50 m, 100 m, and 150 m, and each interval is repeated 8 times. The gaps between the objects play a role of microgrooves. Accordingly, the interval, height, and length of the objects are respectively equal to the width, height, and length of the square-shaped microgrooves. In addition, the both sides of the microgroove are gradually open due to the diamond-shaped edges of the object. The squareshaped microgrooves cannot be machined with a rotational tool since the revolving radius of the diamond tip is too large to keep the shape of microgrooves. Consequently, the microgrooves are machined with a non-rotational cutting tool. The bank and square-shaped microgrooves are fabricated by the non-rotational cutting. Figure 12 shows the non-rotational tool employed for the fabrication of them. The tool is attached to the C table through a jig, and the workpiece is mounted on the B table. As illustrated in Fig.11 (b) and (c), one diamond-shaped edge and the bodies of the objects are machined, and the
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151 Table 2. Cutting conditions for machining square-shaped microgrooves
Feed speed Depth of cut
Rough cut
40 mm/min
Finish cut
1.0 mm/min
Rough cut
1.0 m
Finish cut
0.5 m
40 μm A
A
40 μm
(d)
μm
6.0
Height
(a) Oblique view of the array (b) Top view of the array
3.0
Depth:4.95 μm
1.5 0 20
40 60 80 Distance μm
good surface. Figure 13 (c) shows the profile of the cross section that is represented as A-A in Fig.13 (b). The depth of the object i.e., the height of the microgrooves is 4.95 m. This proves that the microchannel is precisely fabricated. Figure 13 (d) depicts an enlarged view of the edge of the object between the microgrooves. From the figure, it is seen that the diamond shape of the object is sharply fabricated though its edge is a little wavelike shape with burr in nanometer order. This is due to the ductility of gold. However, they do not affect the evaluation of blood fluidity. The microchannel is actually used for the evaluation of the blood fluidity. The cover glass is well fitted with the chip and the blood flows smoothly. It is found that the microchannel chip is valid for the evaluation. 5. Conclusions
4.5
0
151
2 μm
(c) Profile of cross section A-A (d) Enlarged view of an edge of the object Fig. 13. Several views and measurements of actually machined squareshaped microchannel
other edge of them is fabricated, using the translational and rotational axes to feed the tool. In case that the gap between the objects, i.e., the width of square-shaped microgroove, is more than 50 m, the gap is not completely formed by only the cutting illustrated in Fig.11 (b) and (c), that is, unmachined part is left. Since the width of the diamond tip on the non-rotational tool is 19 m, as shown in Fig.12, thus the unmachined part is removed with the non-rotational tool so as to make a flat surface. 4.2. Machining of microchannel and blood fluidity evaluation Table 2 lists the cutting conditions employed for machining the microgrooves. Material of the chip is gold. Figure 13 (a) and (b) depict the parts of actually machined square-shaped microchannel, whose width is 25 m. As seen from the figure, it is found that the microchannel is well machined as designed and has very
As examples of applying ultraprecision microgrooving technology to bio fields, two cases are introduced, dental implants and microchannel chips. The reason to employ the traditional cutting technology is the high possibility of selecting various kinds of metals and creating complicated shapes with high dimensional accuracy and surface quality. As seen from machined results, it is found that the ultraprecision micromachining technology has the potential of producing a variety of bio-related parts as well as mechanical parts and optical elements. Acknowledgements The authors would like to express their sincere appreciation to former students, Mr. T. Kumon and Mr. F. Ando for their earnest cooperation. References [1] Dornfeld, D., Min, S., Takeuchi, Y., 2006. Recent Advances in Mechanical Micromachining (Keynote), CIRP Annals Manufacturing Technology, Vol. 54, Issue 2, p. 745. [2] Yoshinari, M., Miyayama, N., Oda, Y., Inoue, T., Matsuzaka, K., Shimono, M., 2000. Surface Modification of Titanium Implants with Dry Process, Quintessence of Dental Technology, Vol. 25, p. 1043-1048. [3] Sawada, K., Takeuchi, Y., 1998. Ultraprecision Machining Center and Micromachining, Nikkan Kogyo Shinbun Publisher, p. 9 (in Japanese).
Procedia CIRP 5 (2013) 147 – 151
The First CIRP Conference on Biomanufacturing
Application of ultraprecision microgrooves to dental implant and blood inspection Tohru Ishidaa, Koji Teramotob, Keiichi Nakamotoc, Yoshimi Takeuchid,* a
Tokushima University, 2-24 Shinkura, Tokushima 770-8501, Japan Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan c Tokyo University of Agriculture and Technology, 2-24-16 Naka, Koganei 184-8588, Japan d Chubu University, 1200 Matsumoto, Kasugai 487-8501, Japan * Corresponding author. Tel.: +81-568-51-9666; fax: +81-568-51-1194. E-mail address: [email protected]. b
Abstract Ultraprecision micromachining technology is expected to be a potential tool of producing bio-related parts though it is a traditional one. The characteristic of the ultraprecision micromachining technology is the high possibility of selecting various kinds of metals and creating complicated shapes with high dimensional accuracy and surface quality. The study introduces two cases, dental implants and microchannel chips, by means of ultraprecision microgrooves as applications of ultraprecision micromachining technology. As seen from machined results, it is found that the ultraprecision microgrooving technology has the potential of producing a variety of bio-related parts as well as mechanical parts and optical elements. © 2013 2012The TheAuthors. Authors. Published by Elsevier © Published by Elsevier B.V. B.V. Selection and/or peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Bartolo Selection and/orPaulo peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Paulo Bartolo Keywords: Ultraprecision micromachining ; Microgroove ; Bio-related parts ; Dental implant ; Blood inspection
1. Introduction In these days, ultraprecision micromachining technology is playing an important role to produce precision parts and optical elements such as diffraction grating, micro Fresnel lens and so on [1]. From now on, the application of ultraprecision micromachining technology to bio fields is now expected to a great extent. Here, let us introduce two kinds of examples of ultraprecision microgrooving technology. One is the creation of microgrooves for dental implants, which are the artificial tooth roots inserted to the jawbone. Dental implants easily allow bacteria to intrude to the gingival surface, thus resulting in the dissolution of tooth bone. As a result, dental implants are easily removed. To cope with the problem, it is desirable to make microgrooves around the circumferential surface of dental implants and to block the intrusion of bacteria biologically by developing epithelium cells or
Implants
Titanium Implant
Intrusion of bacteria
Microgrooves Gingiva Teeth
Bone tissues
Bone tissues Gingiva
Jaw Bone
Fig. 1. Dental implants
fibroblasts in the direction of microgrooves, as shown in Fig. 1 [2]. As the first step, compound V-shaped microgrooves are created on a plane surface. The other application is to develop micro-rheology d ev ic e to me a su r e b lo o d f lu id i t y in ter ms o f investigating flow mechanism of blood, as illustrated in
2212-8271 © 2013 The Authors. Published by Elsevier B.V. Selection and/or peer-review under responsibility of Professor Mamoru Mitsuishi and Professor Paulo Bartolo doi:10.1016/j.procir.2013.01.030
148
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
C
Rotational tool
Non-rotational tool Z
Workpiece
Y B X Fig. 3. Setups of ultraprecision cutting (a) Rotational tool; (b) Nonrotational tool Microscope ( 2000)
Glass plate 45
Red corpuscle
mm
8m
m
( )
ih
i
l
l
(b)
ih
i
50 μm
50 μm
50 μm
Fig. 2. Configuration of microchannel chip to inspect corpuscle flow
2. Ultraprecision machining center and machining method Figure 3 illustrates setups in cutting with the ultraprecision machining center used for the experiments. The utilized machining center is ROBONANO by FANUC Ltd., and has five axes, i.e., X, Y, and Z axis as translational axes, and B and C axis as rotational ones.
l
50 μm
Mirror surface
Mirror surface
150
2 μm 90
2 μm
1 mm
0.42 μm
Fig. 2. The device allows human blood flow to pass through microchannel array built on a chip as a model of capillary vessels due to its shape, where many microgrooves are arranged in parallel. At the same time, the blood flow through the microchannels can be visually observed, which can evaluate its fluidity. Consequently, the employment of microchannel array chips made of various metals is expected to evaluate the compatibility between blood and metals. However, a microchannel array, i.e., arrangement of a lot of microgrooves, is generally built on silicon by means of photolithographic techniques, which results in low controllability of the shape of the microgrooves. The shape and accuracy of the microgroove are extremely important to measure blood fluidity with a microchannel array chip. To solve the problem, the study aims at fabricating the microchannel array chip by ultraprecision machining.
l
Fig. 4. Difference in methods to make V-shaped microgrooves (a) Rotational tool; (b) Non-rotational tool
90
2 μm 90
0.42 μm
16
Fig. 5. Configuration of compound microgrooves
The positioning resolutions of the translational axes and the rotational axes are 1 nm and 0.00001 , respectively. The machining center is designed, based on the concept of friction-free servo structures. Namely, pneumatic air bearings are adopted for the rotational and translational axes and the other movements, thus resulting in elimination of solid friction completely [3]. As illustrated in Fig. 3, the machining center has two type cutting methods according to the employed tool, that is, rotational tool or non-rotational tool. The former is attached to a high-speed air turbine spindle mounted on C table, as shown in Fig. 3 (a). The latter is directly fixed on C table through a jig, as shown in Fig. 3(b). A workpiece is mounted on B table in both cases. Figure 4 represents the appearances in machining a V-shaped microgroove with the former and the latter, respectively. Both tools are equipped with a diamond tip, which has cutting edge of 90 in nose angle. In case of the former, the microgrooving is carried out with the tool rotating, as
149
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
Trapezoid grooving C table
Workpiece 2 μm
Diamond cutting tool
2 μm
(a) Left slope (b)
Workpiece
(c)
V-shaped grooving
Pickfeed directions 2 μm
Fig. 6. Machining method of microgrooves
illustrated in Fig. 4 (a), and in case of the latter, it is done with the tool not rotating, as illustrated in Fig. 4(b). The same V-shaped microgroove of 90 in bottom angle can be machined in both cases.
(c) Right slope
Fig. 7. Machined V-shaped microgrooves (material: 18k-gold alloy) (a) Left slope; (b) Top surface; (c) Right slope Table 1. Cutting conditions Workpiece
As illustrated in Fig. 5, compound microgrooves in the study consist of trapezoid grooves having V-shaped microgrooves. The size of V-shaped microgrooves is 2 m in pitch and 90 at groove angle. Every trapezoid groove is 150 m in pitch with the plateau length of 50 m and groove angle of 30 . Trapezoid bottom parts are required to be a mirror surface. The shape of compound microgrooves is determined from the viewpoint of fabricating a simplified model of dental implants. To carry out compound V-shaped microgrooving, a high speed air turbine spindle with a trapezoid- shaped diamond cutting tool is mounted on C table, as shown in Fig. 6. In this case, three translational axes are used: X axis for the tool feed direction, Z axis for the pitch control and Y axis for the depth of cut. After the trapezoid microgrooves are completed, the diamond cutting tool is changed to a 90 V-shaped one in order to fabricate V-shaped microgrooves on trapezoid groove surfaces. Grooving is carried out in the down-cut manner. The work material used is 18K gold alloy. 3.2. Machined result and cell cultivation experiment Figure 7(a), (b) and (c) show SEM images of machined compound V-shaped microgroove surfaces under the cutting condition listed in Table 1. From these figures, it is seen that the fine microgrooves can be fabricated on the trapezoid groove surface. The machined compound grooves have smooth surfaces and sharp edges without any burr generation. The surface
Spindle rotation
45,000 rpm
Feed speed
50 mm/min
Depth of cut
Trapezoid
V-shaped
Rough cut
10 m
1.0 m
Finish cut
1.0 m
0.5 m
Without microgrooves
3.1. . Configuration of compound V-shaped microgrooves and machining method
18k-gold alloy
With microgrooves
3. Creation of microgrooves for dental implants
Polystyrene cultivation bed
Z (PF) X
(a)
Fee d dire ctio n
Workpiece
(b) Top surface
Fig. 8. Growing cells with and without V-shaped microgrooves
roughness of the bottom part in trapezoid microgrooves was approximately 15 nmRmax, which shows the mirror surface finish. About 30hours was spent to fabricate the grooves. In case of V-shaped grooving on the trapezoid slope, there are two pickfeed directions: upward direction and downward one along the trapezoid slope. The former could achieve better machining surface, compared with the latter. In the latter, some burrs took place along the edge and groove surface. Thus, it is preferable to select the upward pickfeed direction.
150
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151
Polystyrene cultivation bed
Non-rotational tool
100 μm
(a) Machining of the bank Non-rotational tool
Tool trajectory
(b) Machining of the diamond shape on one side
Fig. 9. Accumulative cells on compound microgrooves
Glass contact surface
Square-shaped microgrooves
Bank
(c) Machining of the diamond shape on the other side
10 μm
Fig. 11. Machining method of bank and square-shaped microgrooves
Shank
5 μm
Shank
100 μm
90º 15 μm 100 μm 100 μm
200 μm
19 μm Diamond
10 mm
Diamond
Diamond tip
Fig. 12. Non-rotational tool employed to machine microgrooves Fig. 10. Dimension of microchannel
A cultivation bed of polystyrene is produced from a metal mold of the machined compound V-shaped microgrooves in order to carry out cultivation experiments by use of it. Figure 8 shows an experimental result, where the epithelium cells on the pale part without microgrooves grow up in the random direction. On the other hand, cells on V-shaped microgrooves grow up along the direction of microgrooves. As shown in Fig. 9, it is also seen that cells form the accumulative layers on the bottom part of trapezoid groove. It is confirmed that cells can be controlled to the intended direction by using compound V-shaped microgrooves. 4. Creation of microchannel chip for micro-rheology device 4.1. Shape of microchannel and machining plan Figure 10 illustrates the dimensions of the designed microchannel, which consists of square-shaped microgrooves. The designed chip has the slender rectangular-prism-shaped objects on the bank. The
object is 10 m in width, 5 m in height, and 100 m in length, and has diamond-shaped edges. The objects are arranged at several intervals of 25 m, 50 m, 100 m, and 150 m, and each interval is repeated 8 times. The gaps between the objects play a role of microgrooves. Accordingly, the interval, height, and length of the objects are respectively equal to the width, height, and length of the square-shaped microgrooves. In addition, the both sides of the microgroove are gradually open due to the diamond-shaped edges of the object. The squareshaped microgrooves cannot be machined with a rotational tool since the revolving radius of the diamond tip is too large to keep the shape of microgrooves. Consequently, the microgrooves are machined with a non-rotational cutting tool. The bank and square-shaped microgrooves are fabricated by the non-rotational cutting. Figure 12 shows the non-rotational tool employed for the fabrication of them. The tool is attached to the C table through a jig, and the workpiece is mounted on the B table. As illustrated in Fig.11 (b) and (c), one diamond-shaped edge and the bodies of the objects are machined, and the
Tohru Ishida et al. / Procedia CIRP 5 (2013) 147 – 151 Table 2. Cutting conditions for machining square-shaped microgrooves
Feed speed Depth of cut
Rough cut
40 mm/min
Finish cut
1.0 mm/min
Rough cut
1.0 m
Finish cut
0.5 m
40 μm A
A
40 μm
(d)
μm
6.0
Height
(a) Oblique view of the array (b) Top view of the array
3.0
Depth:4.95 μm
1.5 0 20
40 60 80 Distance μm
good surface. Figure 13 (c) shows the profile of the cross section that is represented as A-A in Fig.13 (b). The depth of the object i.e., the height of the microgrooves is 4.95 m. This proves that the microchannel is precisely fabricated. Figure 13 (d) depicts an enlarged view of the edge of the object between the microgrooves. From the figure, it is seen that the diamond shape of the object is sharply fabricated though its edge is a little wavelike shape with burr in nanometer order. This is due to the ductility of gold. However, they do not affect the evaluation of blood fluidity. The microchannel is actually used for the evaluation of the blood fluidity. The cover glass is well fitted with the chip and the blood flows smoothly. It is found that the microchannel chip is valid for the evaluation. 5. Conclusions
4.5
0
151
2 μm
(c) Profile of cross section A-A (d) Enlarged view of an edge of the object Fig. 13. Several views and measurements of actually machined squareshaped microchannel
other edge of them is fabricated, using the translational and rotational axes to feed the tool. In case that the gap between the objects, i.e., the width of square-shaped microgroove, is more than 50 m, the gap is not completely formed by only the cutting illustrated in Fig.11 (b) and (c), that is, unmachined part is left. Since the width of the diamond tip on the non-rotational tool is 19 m, as shown in Fig.12, thus the unmachined part is removed with the non-rotational tool so as to make a flat surface. 4.2. Machining of microchannel and blood fluidity evaluation Table 2 lists the cutting conditions employed for machining the microgrooves. Material of the chip is gold. Figure 13 (a) and (b) depict the parts of actually machined square-shaped microchannel, whose width is 25 m. As seen from the figure, it is found that the microchannel is well machined as designed and has very
As examples of applying ultraprecision microgrooving technology to bio fields, two cases are introduced, dental implants and microchannel chips. The reason to employ the traditional cutting technology is the high possibility of selecting various kinds of metals and creating complicated shapes with high dimensional accuracy and surface quality. As seen from machined results, it is found that the ultraprecision micromachining technology has the potential of producing a variety of bio-related parts as well as mechanical parts and optical elements. Acknowledgements The authors would like to express their sincere appreciation to former students, Mr. T. Kumon and Mr. F. Ando for their earnest cooperation. References [1] Dornfeld, D., Min, S., Takeuchi, Y., 2006. Recent Advances in Mechanical Micromachining (Keynote), CIRP Annals Manufacturing Technology, Vol. 54, Issue 2, p. 745. [2] Yoshinari, M., Miyayama, N., Oda, Y., Inoue, T., Matsuzaka, K., Shimono, M., 2000. Surface Modification of Titanium Implants with Dry Process, Quintessence of Dental Technology, Vol. 25, p. 1043-1048. [3] Sawada, K., Takeuchi, Y., 1998. Ultraprecision Machining Center and Micromachining, Nikkan Kogyo Shinbun Publisher, p. 9 (in Japanese).