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Abstract
This paper presents the design, manufacturing, and characterization of a three-dimensional (3D)-printed and electromagnetically actuated adjustable optical slit structure. The device comprises magnet-attached slits connected to the main frame via two springs controlled by external coils. To analyze the forces acting on the springs and simulate the mechanical behavior of the device, we developed both analytical and finite-element models. After fabricating the device using fused deposition, we conducted a series of tests to evaluate its performance. These tests included (1) analyzing the opacity of the slit blade as a function of its thickness, (2) measuring the temperature increase resulting from the power applied to the coils to determine the operable range of the structure, and (3) evaluating the hysteresis, repeatability, and resolution (minimum step) of the device. The experimental works were crucial to assessing the device’s practicality and optimizing its performance for specific applications, which reveals a maximum slit width of ${\sim}450\;{\unicode{x00B5}{\rm m}}$, with ${\sim}6.4\;{\unicode{x00B5}{\rm m}}$ step size within this study. Overall, our developed slit device has the potential to be useful in various optics-related laboratories due to its compatibility with conventional 1-inch (25.4 mm) diameter optomechanical mounts, compact form, low power consumption, and rapid prototyping capability with hybrid materials in a cost-friendly fashion, owing to the 3D-printing technology. We discuss an application where the adjustable slit is employed in a combined laser-scanning microscope and a spectrometer, highlighting its versatility and potential for the future.
© 2023 Optica Publishing Group
1. INTRODUCTION
Optical slits, diaphragms, and pinholes are widely used optomechanical components from which light can be transmitted through their aperture. They are utilized for common applications in various optical systems and instruments, such as optical spectrometers and monochromators [1]. These devices comprise two (for slits) or more (for pinholes) edge structures, whose distance can be altered to control the amount and the spatial profile of the incoming light [2–5].
In earlier times, static slit arrays [6], and microslit masks [7] were demonstrated, offering the experimenter to choose between a plethora of different aperture options on the same plane by aligning the incoming light onto the desired feature. On the other hand, commercial adjustable slits and diaphragms can be adjusted by screwing micrometer heads to control their width [8–10]. With the advances in microfabrication technology, tunable optical slit mechanisms were presented [11] using fluidic [12], electrowetting [13], electrothermal [14], electrostatic [15], and electromagnetic [16,17] actuation principles. As tabulated in Table 1, these microfabricated bioparts necessitate high actuation voltages.
Table 1. Comparison of Adjustable Slits, Diaphragms, and Pinholes in the Literature
During the last decade, thanks to its manufacturing speed, accessibility, and cost, three-dimensional (3D) printing has become a popular choice in building optical (i.e., lenses, waveguides, filters, and various mechanical components [19–27]) sensing [28–31] and actuation [32–38] applications. In this study, we present a tunable optical slit structure based on the electromagnetic actuation principle. Our device is not only compatible with a conventional 1-inch diameter optomechanical mount but also can be rapidly fabricated with hybrid materials. Thermoplastic polyurethane (TPU) is used at the flexure part to facilitate the desired range of motion (up to 450 µm slit width) at a low applied electrical power of ${\sim}490\;{\rm mW}$, owing to its low Young’s modulus. PLA (as the harder material) is utilized in both the slit itself and the overall frame of the device. In the following sections, we will introduce the device concept, model the electromagnetic forces acting on the slits, simulate the structure using finite-element modeling (FEM), share the manufacturing and assembly details, and finally present the acquired results, including the maximum slit width, step size, and cycle-to-cycle repeatability.
2. PROPOSED DEVICE
Figure 1 illustrates the 3D-printed tunable slit structure. This structure is designed in five different parts: (1) a slit body, (2) four springs, (3) two electrocoils, (4) two Nd magnets, and (5) two slit blades as indicated in Fig. 1. The design parameters affecting the performance of the structure are shown in the same figure, and the parameters are tabulated with their dimensions in Table 2. The slit body is designed to suit a 1-inch optomechanical mount with a 10 mm thickness. Therefore, the diameter of the slit body (${D_b}$) is selected to be 25.4 mm, and the wall thickness (${w_w}$) is chosen as 1 mm to provide a sturdy frame. On the side surface of the cylindrical frame, multiple channels (${w_{\textit{bc}}}$) are grooved to locate the legs of the coils. The only thermoplastic urethane (TPU)-based part, the spring, connects the slits to the device frame. The height (${h_s}$) and width (${w_s}$) of the spring and the gap between the adjacent spring sections (${w_{\textit{sg}}}$) are chosen to be 8, 1, and 1.5 mm considering the manufacturing limits and the overall device dimension, respectively. The transparency of the slit blade as a function of its thickness is characterized (see Section 4) based on which the slit blade thickness is selected as 1.5 mm (${t_b}$). A slit width of 2 mm (${w_b}$) is used to support up to an optical beam diameter of 4 mm. An electrocoil having a 22 mH inductance (having a diameter ${D_c}$ of 7 mm, and a height ${h_c}$ of 8 mm) and a Neodymium magnet (1 mm in height ${h_m}$, 2 mm in diameter ${D_m}$) are used. In the next section, we focus on modeling the forces on the slit and finite-element-method (FEM) simulations of the tunable slit.
Fig. 1. Conceptual drawing of the optical slit structure. (a) Top view of the structure indicating the notations of the parts: (1) slit body, (2) spring, (3) electrocoil, (4) Nd magnet, and (5) slit blade. Subfigures of (b) and (c) demonstrate the side views of the device from different perspectives.
Table 2. Design Parameters and Values of the Proposed Tunable Slit, Illustrated in Fig. 1
3. MODELING AND SIMULATION
The magnet-to-magnet force can be modeled through considering the superposition of all four force combinations between each pole of the adjacent magnets, such that [39,40]
Fig. 2. Forces acting on the slit as a function of magnet-to-center position. The shaded region on the plot corresponds to a nonphysical (negative slit width) region due to physical limitations. Thin-dashed, straight, and double lines represent the magnet-to-magnet (${F_{\textit{mm}}}$), ferrite-to-magnet (${F_{\textit{fm}}}$), and electrocoil-to-magnet forces (${F_{\textit{em}}}$), respectively. Thick-dashed line shows the total force: ${F_{\rm{total}}} = {F_{\textit{mm}}} - {F_{\textit{fm}}} + {F_{\textit{em}}}$. (Right half of the slit is plotted.)
The third force component arises due to the magnetic force generated by the electrocoil on the magnet and is plotted using the Lorentz force equation:
where $i$ is the applied current, $L$ is the wire length of the coil measured as 31.15 m long, and $B$ is the magnetic flux density. $B$ was monitored using a gaussmeter with 0.5 mm intervals and was fitted to an exponential curve [${\rm B} = 0.0416 \cdot {\rm exp}(- 1054 \cdot {x_{\textit{cm}}}$)] based on empirical measurements. We took a representative $i$ value as 12 mA, which was experimentally observed to widen the slit width by 100 µm.Figure 2 illustrates all three force components as a function of the magnet-to-center distance, ${x_{\textit{cm}}}$. We use the following conversions in plotting the forces with a common $x$ axis: ${x_{\textit{mm}}} = 2 \cdot {x_{\textit{cm}}}$, ${x_{\textit{cf}}}\, = {x_{\textit{cm}}} + {h_m} + {x_{\textit{fm}}}$, and ${x_{\textit{fm}}} = - {x_{\textit{cm}}} + 2.7\;{\rm mm}$. Overall, we observe that the forces (apart from the spring force) balance each other at the rest position (total force shows minima at ${x_{\textit{cf}}} = 2\;{\rm mm}$) where the slits are adjacent to each other. During the course of actuation, the slit blade starts moving toward the electrocoil (through the $x$ axis) depending on the applied power.
The springs that are attached to the blade and the Nd magnet are simulated using finite-element analysis via COMSOL Multiphysics software, as illustrated in Fig. 3. Within the simulation, three different materials—TPU, PLA, and Nd—are used for springs, blades, and magnets, respectively. The material properties we assigned in the simulation are tabulated in Table 3 [41]. The spring constant is obtained to be 8.826 N/m. A maximum accumulated stress of 264 kPa, which is significantly lower than the tensile strength of TPU (39 MPa ultimate, 8.6 MPa yield, based on the manufacturer specifications), is observed when an external load of ${F_{\rm{applied}}} = 10\;{\rm mN}$ is applied in the ${+}x$ direction, leading to a displacement of 1.133 mm.
Table 3. Material Properties of the Proposed Slit, Illustrated in Fig. 3
4. EXPERIMENTAL SETUP AND RESULTS
The components of the device are assembled before building the experimental setup. Figure 4 demonstrates the nonassembled components of the proposed slit device. In the assembly process, first, the coil is inserted into the body. Then the Nd magnets are fixed onto the side wall of the slit blade. Afterwards, the springs are engaged with the body and the blade. Finally, the prepared slit device is placed into a conventional 1-inch optomechanical mount.
Fig. 4. View of the components of the nonassembled slit device: (a) electrocoil, (b) slit body, (c) springs, (d) Nd magnet, and (e) slit blade.
Fig. 5. Experimental setup: (a) device under test placed in a microscope setup and (b) view of the manufactured slit device mounted in an optomechanical component.
Fig. 6. Preliminary experimental calibration: (a) light transmission through the PLA material as a function of its thickness and (b) temperature of the coil as a function of the applied power. The shaded region represents the temperatures where glass transition is observed.
Figure 5 displays (a) the experimental test setup and (b) the manufactured slit device placed into the mount that is able to use in the optical system. The test setup comprises i) the manufactured slit device, ii) a 3D stage in order to hold the slit, iii) a function generator to drive current to the coils, and iv) a digital microscope to monitor the aperture width as displayed in Fig. 5(a).
On the display of the digital microscope, the slit was monitored and stored as an 8-bit grayscale image in MATLAB. The width was determined by observing the number of pixels exceeding a given threshold (number of bright valued pixels) for a given horizontal cross section.
Fig. 7. Plot of the increasing and decreasing (hysteresis) slit gap as a function of applied power to the coils. Error bars show the standard deviation of eight different measurements.
Fig. 8. Exemplary use of the adjustable slit in a laser-scanning and spectrometer application. Through adjustment of the slit width, one can obtain a laser-scanned image of the sample (slit open, galvo mirrors scanning) or obtain the spectrum of a point on the sample (slit narrow, rotating diffraction grating, galvo mirrors stationary). M#, mirror; GSM, galvo scanning mirror; SC, scan lens; TL, tube lens; DM, dichroic mirror; OL, objective lens; XYZ, three-axis motorized stage; CO, collection optics; CM#, concave mirror; DG, diffraction grating; PMT, photomultiplier tube.
Two preliminary experiments were conducted to determine the thickness of the slit by observing its transmission characteristics and observing the temperature increase as a function of applied electrical power to the coil to determine the highest applicable power before the glass transition. The parameter of ${t_b}$ corresponding to the thickness of the blade is characterized by the percentage of the light that passes through the material as shown in Fig. 6(a). In this plot, the transmission is measured as 100%, 2.72%, 0.0152%, 0.0023%, 0.0001%, and 0% under the 0, 0.5, 1, 1.5, 2, and 2.5 mm thick PLA materials, respectively. Based on the measurements, the blade was adjusted to be 1.5 mm thick to achieve ${\lt}0.01\%$ transmission. This thickness is selected rather than the thicker options due to prevent the sag arising from the extra mass. While we utilized a gray PLA filament mainly due to its availability in our laboratory, the use of a highly absorbing black PLA would further improve light blockage and allow for the use of a thinner slit layer.
Figure 6(b) plots the temperature increase on the coil, as observed by an infrared thermometer, as a function of the applied power to the coils to determine the operable range. Overheating the coil restraints to work in full performance leads to a glass transition of the PLA parts (${\lt}50^\circ {\rm C}$ in temperature as reported in its datasheet) based on the acquired data. Therefore, the power limit was selected as ${\sim}500\;{\rm mW}$ to refrain from glass transition.
To observe the changes in the slit aperture, the function generator produces a triangular wave, without loss of generality at 20 mHz frequency, with 14 V peak-to-peak and 3 V DC offset voltages (voltage changes between ${-}{4}$ to 10 V) for eight periods. The applied voltage range is based on the maximum voltage that can be generated by the function generator. We note that the blades were initially located about 200 µm away from each other due to imperfections in the assembly process; thus, the minimum voltage of ${-}{4}\;{\rm V}$ ensured the contact between the slits. In Fig. 7, hysteresis behavior was plotted as well, where different colors are assigned to the widening and narrowing of the slit gap. Various instances of the slit gap (100 µm, 200 µm, and 400 µm) displayed on the digital microscope are shown as insets within the same figure. Under a static magnetic field, the Lorentz force equation dictates a linear relationship between the force and the applied current. Accordingly, we expect a square-root relationship between the force and the applied power to the coil, which is coherent with that observed in Fig. 7. We attribute the deviation from the square-root behavior due to i) the change of observed magnetic field in the tested slit gap range and ii) the various force components acting on the blades apart from the spring force that results in a nonlinear relationship between the force and the slit gap.
The resolution of the device that corresponds to the minimum step size is calculated based on ${\pm}$ one standard deviation ($\sigma$). The average standard deviation is found to be 6.4 µm (${\pm}3.2\;{\unicode{x00B5}{\rm m}}$), and the error bars are plotted at some selected positions as in Fig. 7.
5. EXAMPLE APPLICATION
Our slit device was initially developed for use in combined two-photon microscopy [42,43] and rotating grating spectrometer setup. Figure 8 illustrates a sketch of a setup with a near-infrared laser source ($\lambda = 1032\;{\rm nm}$). This figure presents the laser transmission from the source to the target specimen, passing through mirrors 1-4, galvoscanning mirrors, a scan lens, a tube lens, and the objective lens, respectively [44,45]. Then the emitted photons from the specimen are scattered back, being directed toward the spectrometer via the dichroic mirror. The spectrometer embarks two concave mirrors, a rotating diffraction grating, and a detector [i.e., a photomultiplier tube (PMT)] that detects the transmitted photons passing the slit aperture [46]. The slit is located in front of the PMT, such that for two-photon imaging, the slit should be wide open (i.e., 300–450 µm wide), and to observe the spectrum of a desired point on the specimen, the slit must narrow down (i.e., 10–50 µm wide) to permit a narrow wavelength band at a time while the grating is rotating.
6. DISCUSSION
In this section, we discuss the cost and turn-around time, reliability, potential measures on outgassing, and position feedback regarding our device.
Cost and turn-around time: A number of studies estimate the manufacturing cost of microelectronic chips based on processing duration, number of utilized clean room machines, steps of manufacturing process, labor required, wafer size, and chip size. Accordingly, the cost of fabrication of a microelectronic chip is estimated to be as low as the $ \$ 0.50{-}\$ 2 $ range [47,48].
On the other hand, a comparable slit size to that presented in this study, together with spring structures, would necessitate a large MEMS chip (i.e., spanning an area larger than ${5}\;{\rm mm} {\times} {5}\;{\rm mm}$). Fabrication and packaging of such large MEMS devices may cost as high as $ \$ 70{-}\$ 100 $ [49]. The sale price of a manual or motorized opto-mechanical adjustable slit is $ \$ 300{-}\$ 4000 $ (Thorlabs products VA100 and BP209), suggesting that the bill of materials is comparable to, if not larger than, that of large MEMS devices. In comparison, the bill of materials for our device having 25 mm diameter is only $ \$1 $ including the material cost, the embedded coils, and the cost of the operator per manufacturing duration of the device. The 3D-printing technique also offers an advantage in design-to-device turn-around time, especially at the development stages of the device. While it typically takes lots of iterations (on the order of weeks) to ensure a high yield, it takes about 1 h to successfully manufacture a 3D-printed actuator.
Relability: In a previous study by our group [50], we conducted cyclic reliability tests of 3D-printed actuators (for laser-scanning purposes). These tests lasted for 108, where devices that experienced less than half the tensile strength could bear all 108 cycles while the lifetime dropped drastically as higher displacements were attempted, in accordance with the Arrhenius law. Based on the von Mises stress analysis shown in Fig. 3, we observe a stress as low as 250 kPa for a total slit width of more than 2 mm, which is beyond the maximum width that is intended for use. We note that specifications of the utilized TPU filament indicate a yield stress of 8.6 MPa that is significantly larger than our FEM predictions. In this regard, we predict our devices to last more than 106 cycles at room conditions. We note that this is a prediction and that reliability testing specific to the presented device will be sought in the future.
Outgassing: Plastics that are used as filaments (i.e., ABS, PLA, PETG, and Nylon) outgas, resulting in volatile organic compounds and ultrafine particles. Yet, the use of aluminum oxide based vacuum sealing resin to coat thermoplastics has proven to improve outgassing performance [51].
Position feedback: A closed-loop position-feedback loop is desired to correctly monitor and adjust the slit width. The position-feedback could simply be implemented via embedding more than one coil, with the expense of shrinking the current coil size and thus the magnetic force. In such a scenario, one or multiple coils could facilitate electromagnetic actuation, while the rest will be spared for sensing the current as an indicator of the position of the magnet on the slits.
7. CONCLUSION
In this work, a 3D-printed and electromagnetically actuated adjustable slit was designed, manufactured, characterized, and tested. The force constituents acting on the device were analytically modeled, and finite-element simulations were conducted of the device. Following its fabrication via fused deposition, the slit thickness and maximum applicable electrical power were determined through preliminary experiments. Finally, the resolution (minimum step size) and maximum range of the device were shown to be ${\sim}6.4\;{\unicode{x00B5}{\rm m}}$ and ${\sim}450$, respectively, revealing a dynamic range of 70. Finally, we discuss an exemplary application where the presented variable slit device plays a key role in transitioning between a laser-scanning microscope and a spectrometer. It is noteworthy to mention that two of the proposed structures can be used simultaneously as a two-dimensional rectangular aperture once they are placed back-to-back and orthogonal to each other.
Thanks to its compact form that can fit into the conventional 1-inch diameter optomechanics, low power consumption, and rapid manufacturing capability with TPU-PLA merged materials in a cost-friendly fashion, the developed adjustable slit can be used in a variety of applications in potentially every optics laboratory.
Funding
Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (120N240).
Acknowledgment
We acknowledge the Scientific and Technological Research Council of Turkey (TüBİTAK) for funding of this work.
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
REFERENCES
1. H. A. Padmore, “Optimization of soft x-ray monochromators,” Rev. Sci. Instrum. 60, 1608–1615 (1989). [CrossRef]
2. M. Kraft, A. Kenda, A. Frank, W. Scherf, A. Heberer, T. Sandner, H. Schenk, and F. Zimmer, “Single-detector micro-electro-mechanical scanning grating spectrometer,” Anal. Bioanal.Chem. 386, 1259–1266 (2006). [CrossRef]
3. M. Mohaupt, U. Zeitner, G. Harnisch, T. Bolz, S. Risse, A. Gebhardt, H. von Lukowicz, T. Peschel, U. Hübner, Y. Gerome, and M. Erhard, “The high precision double slit device of the slit assembly for the FLEX instrument,” Proc. SPIE 11852, 118520K (2021). [CrossRef]
4. S. Daniel, K. Saastamoinen, T. Saastamoinen, J. Rahomäki, A. T. Friberg, and T. D. Visser, “Dynamic control of optical transmission through a nano-slit using surface plasmons,” Opt. Express 23, 22512–22519 (2015). [CrossRef]
5. D. Wang, C. Liu, and Q.-H. Wang, “Adjustable optical slit based on the phase type spatial light modulator,” IEEE Photon. J. 11, 7000408 (2019). [CrossRef]
6. R. Riesenberg and T. Seifert, “Design of spatial light modulator microdevices: microslit arrays,” Proc. SPIE 3680, 406–414 (1999). [CrossRef]
7. R. Riesenberg and A. Wuttig, “Optical sensors with MEMS, slit masks, and micromechanical devices,” Proc. SPIE 4561, 315–322 (2001). [CrossRef]
8. H. W. Yoo, M. E. van Royen, W. A. van Cappellen, A. B. Houtsmuller, M. Verhaegen, and G. Schitter, “Adaptive optics for confocal laser scanning microscopy with adjustable pinhole,” Proc. SPIE 9887, 350–360 (2016). [CrossRef]
9. D. Kang, K. C. Woo, D. H. Kang, C. Park, and S. K. Kim, “Improved spectral resolution of the femtosecond stimulated Raman spectroscopy achieved by the use of the 2nd-order diffraction method,” Sci. Rep. 11, 3361 (2021). [CrossRef]
10. E. J. Davis, M. Jones, D. A. Thiel, and S. Pauls, “Using open-source, 3D printable optical hardware to enhance student learning in the instrumental analysis laboratory,” J. Chem. Educ. 95, 672–677 (2018). [CrossRef]
11. S. Hoshino, “Variable width optical slit mechanism,” US Patent 6,956,688 (October 18, 2005).
12. S. Schuhladen, K. Banerjee, M. Stürmer, P. Müller, U. Wallrabe, and H. Zappe, “Variable optofluidic slit aperture,” Light Sci. Appl. 5, e16005 (2016). [CrossRef]
13. L. Li, C. Liu, M.-H. Wang, and Q.-H. Wang, “Adjustable optical slit based on electrowetting,” IEEE Photon. Technol. Lett. 25, 2423–2426 (2013). [CrossRef]
14. H. Veladi, R. R. A. Syms, and H. Zou, “Fiber-pigtailed electrothermal MEMS iris VOA,” J. Lightwave Technol. 25, 2159–2167 (2007). [CrossRef]
15. G. Zhou, H. Yu, Y. Du, and F. S. Chau, “Microelectromechanical-systems-driven two-layer rotary-blade-based adjustable iris diaphragm,” Opt. Lett. 37, 1745–1747 (2012). [CrossRef]
16. Y. Du and G. Zhou, “A MEMS-driven Hadamard transform spectrometer,” Proc. SPIE 10545, 105450X (2018). [CrossRef]
17. A. A. Uhov, D. K. Kostrin, V. A. Simon, V. A. Gerasimov, and L. M. Selivanov, “Electrically controlled spectral slit for optical spectrometers,” in IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EIConRus) (IEEE, 2020), pp. 185–187.
18. S. Richter, C. Wehe, U. Wolf, T. Nobis, L.-C. Wittig, P. Huebner, A. Froeber, G. Krampert, D. Thiele, J. Muetze, and M. Kempe, “Integrated confocal imaging system,” Proc. SPIE 10931, 130–139 (2019). [CrossRef]
19. Y. Wang, J. Gawedzinski, M. E. Pawlowski, and T. S. Tkaczyk, “3D printed fiber optic faceplates by custom controlled fused deposition modeling,” Opt. Express 26, 15362–15376 (2018). [CrossRef]
20. J. Lu, X. W. Ng, D. Piston, and T. S. Tkaczyk, “Snapshot image mapping spectrometer with 3D printed multifaceted mapping mirror for biomedical applications,” Proc. SPIE 12216, 63–68 (2022). [CrossRef]
21. Y. Taege, S. L. Schulz, B. Messerschmidt, C. Eggeling, and Ç. Ataman, “A miniaturized illumination unit for airy light-sheet microscopy using 3D-printed freeform optics,” in Imaging Systems and Applications (Optica, 2022), paper IW3C-1.
22. R. Hai, G. Shao, H. O. T. Ware, E. H. Jones, and C. Sun, “3D printing a low-cost miniature accommodating optical microscope,” Adv. Mater. 35, 2208365 (2023). [CrossRef]
23. D. Aguirre-Aguirre, D. Gonzalez-Utrera, B. Villalobos-Mendoza, and R. Diaz-Uribe, “Fabrication of biconvex spherical and aspherical lenses using 3D printing,” Appl. Opt. 62, C14–C20 (2023). [CrossRef]
24. J. E. C. Gunderson, D. W. Mitchell, R. G. Bullis, J. Q. Steward, and W. A. Gunderson, “Design and implementation of three-dimensional printable optomechanical components,” J. Chem. Educ. 97, 3673–3682 (2020). [CrossRef]
25. P. Bernard and J. D. Mendez, “Low-cost 3D-printed polarimeter,” J. Chem. Educ. 97, 1162–1166 (2020). [CrossRef]
26. A. C. Roy, N. Kumar, S. B. Subramanya, A. Gupta, A. Kumar, A. Bid, and V. Venkataraman, “Large-area 3D printable soft electronic skin for biomedical applications,” ACS Biomater. Sci. Eng. 8, 5319–5328 (2022). [CrossRef]
27. K. Zhou, X. Wang, X. Jing, F. Wang, Q. Zhang, F. Chen, J. Hao, C. Deng, J. Zhou, and Y. Yu, “Large-aperture, widely and linearly tunable, electromagnetically actuated MEMS Fabry-Perot filtering chips for longwave infrared spectral imaging,” Opt. Express 30, 42541–42552 (2022). [CrossRef]
28. A. M. Kamat, X. Zheng, B. Jayawardhana, and A. G. P. Kottapalli, “Bioinspired PDMS-graphene cantilever flow sensors using 3D printing and replica moulding,” Nanotechnology 32, 095501 (2021). [CrossRef]
29. A. Tuna, O. K. Erden, Y. D. Gokdel, and B. Sarioglu, “3D printed capacitive pressure sensor with corrugated surface,” in 13th Conference on Ph. D. Research in Microelectronics and Electronics (PRIME) (IEEE, 2017), pp. 149–152.
30. S. Peng, Q. Guo, N. Thirunavukkarasu, Y. Zheng, Z. Wang, L. Zheng, L. Wu, and Z. Weng, “Tailoring of photocurable ionogel toward high resilience and low hysteresis 3D printed versatile porous flexible sensor,” Chem. Eng. J. 439, 135593 (2022). [CrossRef]
31. G. D. Liu, C. H. Wang, Z. L. Jia, and K. X. Wang, “An integrative 3D printing method for rapid additive manufacturing of a capacitive force sensor,” J. Micromech. Microeng. 31, 065005 (2021). [CrossRef]
32. J. Savas, R. Khayatzadeh, F. Civitci, Y. D. Gokdel, and O. Ferhanoglu, “Toward fully three-dimensional-printed miniaturized confocal imager,” Opt. Eng. 57, 041402 (2018). [CrossRef]
33. O. Gürcüoğlu, I. D. Derman, M. Altnsoy, R. Khayatzadeh, F. Çivitci, A. C. Erten, and O. Ferhanoğlu, “A 3D-printed 3D actuator for miniaturized laser scanning probes,” Sens. Actuators A 317, 112448 (2021). [CrossRef]
34. X. Cao, S. Xuan, Y. Gao, C. Lou, H. Deng, and X. Gong, “3D printing ultraflexible magnetic actuators via screw extrusion method,” Adv. Sci. 9, 2200898 (2022). [CrossRef]
35. J. Seo, J.-Y. Hwang, and C.-H. Ji, “Electromagnetic 2D scanning micromirror fabricated with 3D printed polymer parts for LiDAR applications,” Sens. Actuators A 348, 113997 (2022). [CrossRef]
36. C. K. Shen, Y. N. Huang, G. Y. Liu, W. A. Tsui, Y. W. Cheng, P. H. Yeh, and J. C. Tsai, “Low-cost 3D-printed electromagnetically driven large-area 1-DOF optical scanners,” Photonics 9, 484 (2022). [CrossRef]
37. A. Pavone, G. Stano, and G. Percoco, “One-shot 3D printed soft device actuated using metal-filled channels and sensed with embedded strain gauge,” 3D Print. Addit. Manuf. (2023).
38. O. Ulkir, “Design and fabrication of an electrothermal MEMS micro-actuator with 3D printing technology,” Mater. Res. Express 7, 075015 (2020). [CrossRef]
39. D. Vokoun, M. Beleggia, L. Heller, and P. Šittner, “Magnetostatic interactions and forces between cylindrical permanent magnets,” J. Magn. Magn. Mater. 321, 3758–3763 (2009). [CrossRef]
40. F. Peker and O. Ferhanoğlu, “Multi-capsule endoscopy: an initial study on modeling and phantom experimentation of a magnetic capsule train,” J. Med. Biol. Eng. 41, 315–321 (2021). [CrossRef]
41. H. J. Qi and M. C. Boyce, “Stress–strain behavior of thermoplastic polyurethanes,” Mech. Mater. 37, 817–839 (2005). [CrossRef]
42. P. S. Tsai, N. Nishimura, E. J. Yoder, E. M. Dolnick, G. A. White, and D. Kleinfeld, “Principles, design, and construction of a two photon laser scanning microscope for in vitro and in vivo brain imaging,” in In vivo Optical Imaging of Brain Function (CRC Press, 2002), pp. 113–171.
43. W. Denk, J. H. Strickler, and W. W. Webb, “Two-photon laser scanning fluorescence microscopy,” Science 248, 73–76 (1990). [CrossRef]
44. C. L. Hoy, W. N. Everett, M. Yildirim, A. Ben-Yakar, J. B. Kobler, and S. M. Zeitels, “Towards endoscopic ultrafast laser microsurgery of vocal folds,” J. Biomed. Opt. 17, 038002 (2012). [CrossRef]
45. M. Yildirim, O. Ferhanoglu, J. B. Kobler, S. M. Zeitels, and A. Ben-Yakar, “Parameters affecting ultrafast laser microsurgery of subepithelial voids for scar treatment in vocal folds,” J. Biomed. Opt. 18, 118001 (2013). [CrossRef]
46. G. Y. Belay, W. Hoving, A. van der Put, M. Vervaeke, J. Van Erps, H. Thienpont, and H. Ottevaere, “Miniaturized broadband spectrometer based on a three-segment diffraction grating for spectral tissue sensing,” Opt. Laser Eng. 134, 106157 (2020). [CrossRef]
47. R. A. Lawes, “Manufacturing costs for microsystems/MEMS using high aspect ratio microfabrication techniques,” Microsyst. Technol. 13, 85–952007. [CrossRef]
48. D. Gajera, “Process costing of microchip,” Graduate Theses, Dissertations, and Problem Reports (2006).
49. R. Andosca, T. G. McDonald, V. Genova, S. Rosenberg, J. Keating, C. Benedixen, and J. Wu, “Experimental and theoretical studies on MEMS piezoelectric vibrational energy harvesters with mass loading,” Sens. Actuators A 178, 76–87 (2012). [CrossRef]
50. G. Kasap, Y. D. Gökdel, M. B. Yelten, and O. Ferhanoğlu, “Reliability testing of 3D-printed polyamide actuators,” IEEE Trans. Device Mater. Reliab. 20, 152–156 (2020). [CrossRef]
51. I. T. Heikkinen, G. Marin, N. Bihari, C. Ekstrum, P. J. Mayville, Y. Fei, Y. H. Hu, M. Karppinen, H. Savin, and J. M. Pearce, “Atomic layer deposited aluminum oxide mitigates outgassing from fused filament fabrication–based 3-D printed components,” Surf. Coat. Technol. 386, 125459 (2020). [CrossRef]
