Name: fabrication of surface acoustic wave devices on lithium niobate
Uploaded: 2020-06-18T13:00:00
Description: Watch this Scientific Journal Video about Fabrication of Surface Acoustic Wave Devices on Lithium Niobate at JoVE.com

The authors are grateful to the University of California and the NANO3 facility at UC San Diego for provision of funds and facilities in support of this work. This work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of UCSD, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542148). The work presented here was generously supported by a research grant from the W.M. Keck Foundation. The authors are also grateful for the support of this work by the Office of Naval Research (via Grant 12368098).

1. SAW device fabrication via the lift-off method
<ol>
	<li>Perform wafer solvent cleaning in a Class 100 clean room facility by immersing the 4&#8221; (101.6 mm) LN wafer into acetone, followed by isopropyl alcohol (IPA), then deionized water (DI water), each in a sonication bath for 5 min. Pick up the wafer and blow the surface dry with nitrogen (N2) gas flow to remove the remaining DI water from the wafer.&#160; 
	CAUTION: Perform the acetone and IPA immersions in a fume hood. Avoid inhalation and sk...

<ol>
	<li>Ding, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standing+surface+acoustic+wave+(SSAW)+based+multichannel+cell+sorting.">Standing surface acoustic wave (SSAW) based multichannel cell sorting.</a> Lab on a Chip. 12 (21), 4228-4231 (2012).</li><li>Langelier, S. M., Yeo, L. Y., Friend, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UV+epoxy+bonding+for+enhanced+SAW+transmission+and+microscale+acoustofluidic+integration.">UV epoxy bonding for enhanced SAW transmission and microscale acoustofluidic integration.</a> Lab on a Chip. 12 (16), 2970-2976 (2012).</li><li>Rezk, A. R., Qi, A., Friend, J. R., Li, W. H., Yeo, L. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uniform+mixing+in+paper-based+microfluidic+systems+using+surface+acoustic+waves.">Uniform mixing in paper-based microfluidic systems using surface acoustic waves.</a> Lab on a Chip. 12 (4), 773-779 (2012).</li><li>Schmid, L., Weitz, D. A., Franke, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sorting+drops+and+cells+with+acoustics:+acoustic+microfluidic+fluorescence-activated+cell+sorter.">Sorting drops and cells with acoustics: acoustic microfluidic fluorescence-activated cell sorter.</a> Lab on a Chip. 14 (19), 3710-3718 (2014).</li><li>Schmid, L., Wixforth, A., Weitz, D. A., Franke, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+surface+acoustic+wave+(SAW)-driven+closed+PDMS+flow+chamber.">Novel surface acoustic wave (SAW)-driven closed PDMS flow chamber.</a> Microfluidics and Nanofluidics. 12 (1-4), 229-235 (2012).</li><li>Shi, J., Mao, X., Ahmed, D., Colletti, A., Huang, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Focusing+microparticles+in+a+microfluidic+channel+with+standing+surface+acoustic+waves+(SSAW).">Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW).</a> Lab on a Chip. 8 (2), 221-223 (2008).</li><li>Friend, J., Yeo, L. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscale+acoustofluidics:+Microfluidics+driven+via+acoustics+and+ultrasonics.">Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics.</a> Reviews of Modern Physics. 83 (2), 647 (2011).</li><li>Ding, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+acoustic+wave+microfluidics.">Surface acoustic wave microfluidics.</a> Lab on a Chip. 13 (18), 3626-3649 (2013).</li><li>Destgeer, G., Sung, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+microfluidic+actuation+and+micro-object+manipulation+via+surface+acoustic+waves.">Recent advances in microfluidic actuation and micro-object manipulation via surface acoustic waves.</a> Lab on a Chip. 15 (13), 2722-2738 (2015).</li><li>Connacher, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro/nano+acoustofluidics:+materials,+phenomena,+design,+devices,+and+applications.">Micro/nano acoustofluidics: materials, phenomena, design, devices, and applications.</a> Lab on a Chip. 18 (14), 1952-1996 (2018).</li><li>White, R. M., Voltmer, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+piezoelectric+coupling+to+surface+elastic+waves.">Direct piezoelectric coupling to surface elastic waves.</a> Applied Physics Letters. 7 (12), 314-316 (1965).</li><li>Smith, H. I., Bachner, F. J., Efremow, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+High-Yield+Photolithographic+Technique+for+Surface+Wave+Devices.">A High-Yield Photolithographic Technique for Surface Wave Devices.</a> Journal of the Electrochemical Society. 118 (5), 821-825 (1971).</li><li>Bahr, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+techniques+for+surface-acoustic-wave+devices.">Fabrication techniques for surface-acoustic-wave devices.</a> Proc. Int. Specialists Seminar on Component Performance and Systems Applications of Surface Acoustic Wave Devices. , (1973).</li><li>Smith, H. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+techniques+for+surface-acoustic-wave+and+thin-film+optical+devices.">Fabrication techniques for surface-acoustic-wave and thin-film optical devices.</a> Proceedings of the IEEE. 62 (10), 1361-1387 (1974).</li><li>Wilke, N., Mulcahy, A., Ye, S. R., Morrissey, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+optimization+and+characterization+of+silicon+microneedles+fabricated+by+wet+etch+technology.">Process optimization and characterization of silicon microneedles fabricated by wet etch technology.</a> Microelectronics Journal. 36 (7), 650-656 (2005).</li><li>Madou, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fundamentals of microfabrication: the science of miniaturization. , (2002).</li><li>K&#246;hler, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Etching in Microsystem Technology. , (1999).</li><li>Brodie, I., Muray, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The physics of micro/nano-fabrication. , (2013).</li><li>Dentry, M. B., Yeo, L. Y., Friend, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency+effects+on+the+scale+and+behavior+of+acoustic+streaming.">Frequency effects on the scale and behavior of acoustic streaming.</a> Physical Review E. 89 (1), 013203 (2014).</li><li>Morgan, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Surface acoustic wave filters: With applications to electronic communications and signal processing. , (2010).</li><li>Pekarcikova, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+high+power+effects+on+Ti/Al+and+Ta-Si-N/Cu/Ta-Si-N+electrodes+for+SAW+devices.">Investigation of high power effects on Ti/Al and Ta-Si-N/Cu/Ta-Si-N electrodes for SAW devices.</a> IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 52 (5), 911-917 (2005).</li></ol>

SAW devices fabricated from either method are capable of generating useful traveling waves on the surface, and these methods underpin more complex processes to produce other designs. The resonant frequency is usually a little lower than the designed value, due to the mass loading effect of the metal deposited on top. However, there still some points worth discussing to avoid problems.&#160;
Lift-off method 
The choice of photoresist is important. It is possible to use a p...

Relying on the well-known inverse piezoelectric effect, where the atomic dipoles create strain corresponding to the application of an electric field, piezoelectric crystals such as lithium niobate LiNbO3 (LN), lithium tantalite LiTaO3 (LT), can be used as electromechanical transducers to generate SAW for microscale applications1,2,3,4,5,6. By enabling the generation of displacements up to 1 nm at 10-1000 MHz, SAW-driven vibration overcomes the typical obstacles of traditional ultrasound: small acceleration, large wavelengths, and large device size. Research to manipulate fluids and suspended particles has recently accelerated, with a large number of recent and accessible reviews7,8,9,10.
Fabrication of SAW-integrated microfluidic devices requires fabrication of the electrodes&#8212;the interdigital transducer (IDT)11&#8212;on the piezoelectric substrate to generate the SAW. The comb-shape fingers create compression and tension in the substrate when connected to an alternating electric input. The fabrication of SAW devices has been presented in many publications, whether using lift-off ultraviolet photolithography alongside metal sputter or wet etching processes10. However, the lack of knowledge and skills in fabricating these devices is a key barrier to entry into acoustofluidics by many research groups, even today. For the lift-off technique12,13,14, a sacrificial layer (photoresist) with an inverse pattern is created on a surface, so that when the target material (metal) is deposited on the whole wafer, it can reach the substrate in the desired regions, followed by a &#8220;lift-off&#8221; step to remove the remaining photoresist. By contrast, in the wet etching process15,16,17,18, the metal is first deposited on the wafer and then photoresist is created with a direct pattern on the metal, to protect the desired region from &#8220;etching&#8221; away by a metal etchant.
In a most commonly used design, the straight IDT, the wavelength of the resonant frequency of the SAW device is defined by the periodicity of the finger pairs, where the finger width and the spacing between fingers are both <img align="center" alt="Equation" src="/files/ftp_upload/61013/61013eq2.jpg" />/419. In order to balance the electric current transmission efficiency and the mass loading effect on the substrate, the thickness of the metal deposited on the piezoelectric material is optimized to be about 1% of the SAW wavelength20. Localized heating from Ohmic losses21, potentially inducing premature finger failure, can occur if insufficient metal is deposited. On the other hand, an excessively thick metal film can cause a reduction in the resonant frequency of the IDT due to a mass loading effect and can possibly create unintentional acoustic cavities from the IDTs, isolating the acoustic waves they generate from the surrounding substrate. As a result, the photoresist and UV exposure parameters chosen vary in the lift-off technique, depending upon different designs of SAW devices, especially frequency. Here, we describe in detail the lift-off process to produce a 100 MHz SAW-generating device on a double-sided polished 0.5 mm-thick 128&#176; Y-rotated cut LN wafer, as well as the wet etching process to fabricate the 100 MHz device of identical design. Our approach offers a microfluidic system enabling investigation of a variety of physical problems and biological applications.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Absorber</td>
			<td>Dragon Skin, Smooth-On, Inc., Macungie, PA, USA</td>
			<td>Dragon Skin 10 MEDIUM</td>
			<td></td>
		</tr>
		<tr>
			<td>Amplifier</td>
			<td>Mini-Circuits, Brooklyn, NY, USA</td>
			<td>ZHL&#8211;1&#8211;2W&#8211;S+</td>
			<td></td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Nikon, Minato, Tokyo, Japan</td>
			<td>D5300</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromium etchant</td>
			<td>Transene Company, INC, Danvers, MA, USA</td>
			<td>1020</td>
			<td></td>
		</tr>
		<tr>
			<td>Developer</td>
			<td>Futurrex, NJ, USA</td>
			<td>RD6</td>
			<td></td>
		</tr>
		<tr>
			<td>Developer</td>
			<td>EMD Performance Materials Corp., Philidaphia, PA, USA</td>
			<td>AZ300MIF</td>
			<td></td>
		</tr>
		<tr>
			<td>Dicing saw</td>
			<td>Disco, Tokyo, Japan</td>
			<td>Disco Automatic Dicing Saw 3220</td>
			<td></td>
		</tr>
		<tr>
			<td>Gold etchant</td>
			<td>Transene Company, INC, Danvers, MA, USA</td>
			<td>Type TFA</td>
			<td></td>
		</tr>
		<tr>
			<td>Hole driller</td>
			<td>Dremel, Mount Prospect, Illinois</td>
			<td>Model #4000</td>
			<td>4000 High Performance Variable Speed Rotary</td>
		</tr>
		<tr>
			<td>Inverted microscope</td>
			<td>Amscope, Irvine, CA, USA</td>
			<td>IN480TC-FL-MF603</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Doppler vibrometer (LDV)</td>
			<td>Polytec, Waldbronn, Germany</td>
			<td>UHF-120</td>
			<td>4&#8221; double-side polished 0.5 mm thick 128&#176;Y-rotated cut lithium niobate</td>
		</tr>
		<tr>
			<td>Lithium niobate substrate</td>
			<td>PMOptics, Burlington, MA, USA</td>
			<td>PWLN-431232</td>
			<td></td>
		</tr>
		<tr>
			<td>Mask aligner</td>
			<td>Heidelberg Instruments, Heidelberg, Germany</td>
			<td>MLA150</td>
			<td>Fabrication process is performed in it.</td>
		</tr>
		<tr>
			<td>Nano3 cleanroom facility</td>
			<td>UCSD, La Jolla, CA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Negative photoresist</td>
			<td>Futurrex, NJ, USA</td>
			<td>NR9-1500PY</td>
			<td></td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Keysight Technologies, Santa Rosa, CA, USA</td>
			<td>InfiniiVision 2000 X-Series</td>
			<td></td>
		</tr>
		<tr>
			<td>Positive photoresist</td>
			<td></td>
			<td>AZ1512</td>
			<td>Denton Discovery 18 Sputter System</td>
		</tr>
		<tr>
			<td>Signal generator</td>
			<td>NF Corporation, Yokohama, Japan</td>
			<td>WF1967 multifunction generator</td>
			<td>Wafer Dipper 4&#34;</td>
		</tr>
		<tr>
			<td>Sputter deposition</td>
			<td>Denton Vacuum, NJ, USA</td>
			<td>Denton 18</td>
			<td></td>
		</tr>
		<tr>
			<td>Teflon wafer dipper</td>
			<td>ShapeMaster, Ogden, IL, USA</td>
			<td>SM4WD1</td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication of surface acoustic wave devices on lithium niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale&#8212;and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

The IDT to be measured is designed to have a resonant frequency at 100 MHz, as the the finger width and the spacing between them are 10 &#956;m, producing a wavelength of 40 &#956;m. Figure 1 shows the SAW device and IDT&#160;fabricated using this method.
Using an oscillating electrical signal matched to the resonant frequency of the IDT, SAW can be generated across the surface of the piezoelectric material. The LDV measures the vibration via the Doppler effect on the surface,...

Watch this Scientific Journal Video about Fabrication of Surface Acoustic Wave Devices on Lithium Niobate at JoVE.com

Fabrication of Surface Acoustic Wave Devices on Lithium Niobate

Two fabrication techniques, lift-off and wet etching, are described in producing interdigital electrode transducers upon a piezoelectric substrate, lithium niobate, widely used to generate surface acoustic waves now finding broad utility in micro to nanoscale fluidics. The as-produced electrodes are shown to efficiently induce megahertz order Rayleigh surface acoustic waves.&#160;

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order ...

Our protocol demonstrates the details of fabricating typical surface acoustic wave devices upon piezoelectric substrates especially valuable for people seeking to enter this burgeoning field. Keeping any debris away from the surface during cleaning is crucial in the process of fabrication. To pre-break the wafer, place it on a hotplate at 100 degrees Celsius for three minutes.Then move the wafer to aluminum foil. Place the wafer onto a spin coater. Using a dropper, place negative photoresist onto the wafer covering about 75%of the wafer surface area.To produce a photoresist thickness of approximately 1.3 micrometers, execute the following program on the spin coater:500 rpm with an acceleration of 3, 000 rpm per second for five seconds, followed by 3, 500 rpm with an acceleration of 3, 000 rpm per second for 40 seconds. Bake the wafer by placing it on a hotplate at 100 degrees Celsius. Increase the hotplate temperature to 150 degrees Celsius and maintain that temperature for one minute.Then move the wafer from the hotplate and let the wafer cool in the air to room temperature. Do not place the wafer directly onto the hotplate at 150 degrees Celsius. Let the water cool down in air after heating.To expose the photoresist to ultraviolet energy, transfer the wafer to the mask aligner. With the mask aligner set to deliver light at 375 nanometers, expose the photoresist to an energy dose of 400 millijoules per square centimeter. To bake the wafer, place it on a hotplate at 100 degrees Celsius.After three minutes, transfer the wafer onto aluminum foil where it will cool to room temperature. Place the wafer into a beaker filled with pure RD6 developer. Leave the wafer immersed for 15 seconds while gently shaking the beaker.Remove the wafer from the developer and immerse it in deionized water for one minute. Then rinse the wafer under deionized water flow. Finally, use dry nitrogen flow to remove the remaining water from the wafer.Bake the water again at 100 degrees Celsius. After three minutes, transfer the wafer onto aluminum foil where it will cool to room temperature. Place the wafer into a sputter deposition system and evacuate the chamber to a pressure of five times 10 to the negative six millitorr.Next, flow argon at 2.5 millitorr. Then sputter chromium with a power of 200 watts for five nanometers as an adhesion layer. To form the conductive electrodes, deposit aluminum at 400 nanometers and a power level of 300 watts.Transfer the wafer to a beaker and immerse it in acetone. Sonicate the beaker at medium intensity for five minutes. Rinse the wafer with deionized water and dry the wafer with nitrogen flow.Place the wafer on a hotplate at 100 degrees Celsius for three minutes. Then transfer it onto a piece of aluminum foil and wait for it to cool to room temperature. Place the wafer into a sputter deposition system and evacuate the chamber to a pressure of five times 10 to the negative six millitorr.Flow argon at 2.5 millitorr and then sputter chromium with a power of 200 watts for five nanometers as an adhesion layer. Next, form the conductive electrodes by sputtering gold for 400 nanometers at a power level of 300 watts. Place the wafer on a spin coater.Using a dropper, deposit positive photoresist onto the wafer covering about 75%of the wafer surface area. To produce a photoresist thickness of approximately 1.2 micrometers, execute the following program on the spin coater:500 rpm with an acceleration of 3, 000 rpm per second for 10 seconds, followed by 4, 000 rpm with an acceleration of 3, 000 rpm per second for 30 seconds. Then place the wafer on a hotplate at 100 degrees Celsius.After one minute, transfer the wafer onto aluminum foil where it will cool to room temperature. Transfer the wafer to the mask aligner. With the mask aligner set to deliver light at 375 nanometers, expose the photoresist to an energy dose of 150 millijoules per square centimeter.Place the wafer into a beaker filled with pure AZ300MIF developer. Leave the wafer in the beaker for 300 seconds gently shaking the beaker. Remove the wafer from the developer and immerse it deionized water for one minute.Then rinse the wafer under deionized flow. Finally, use dry nitrogen flow to remove the remaining water from the wafer. Next, immerse the wafer in gold etchant for 90 seconds, gently shaking the beaker.After rinsing the wafer under deionized water flow, use dry nitrogen flow to remove the remaining deionized water from the wafer. Apart from the acetone, photoresist, and developer, the most dangerous reagents are the metal actions which require higher level protection such as neoprene gloves and an apron. Finally, immerse the wafer in chromium etchant for 20 seconds, gently shaking the beaker.Rinse the wafer under deionized water flow. And again, use dry nitrogen flow to remove remaining water. IDTs were fabricated using the methods described.The spacing between the fingers and the fingers themselves are all 10 micrometers in width, resulting in a wavelength of 40 micrometers. A sinusoidal signal was applied to the IDT and a laser Doppler vibrometer was used to measure the amplitude and frequency of the resulting surface acoustic wave. The resonance frequency was found to be 96.5844 megahertz, slightly lower than the design frequency of 100 megahertz.A plot of the vibration on the substrate surface shows a surface acoustic wave propagating from the IDTs. Based on the ratio between the maximum amplitude and the minimum amplitude, the standing wave ratio was calculated to be 2.06. The motion of a sessile droplet actuated by the SAW device was demonstrated.A water droplet of 0.2 microliters was pipetted on lithium niobate about one millimeter away from the IDT. When a SAW propagates and encounters the droplet, it leaks into the liquid at the Rayleigh angle. The jetting angle confirms the presence of a surface acoustic wave.These techniques can be used for the fabrication of megahertz or the surface acoustic wave devices. The process needs to be adjusted if higher frequency acoustic wave actuators are required. This protocol provides two dependable methods for preparing high-frequency surface acoustic wave devices used for micro to nanoscale acoustofluidics research.

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