An official website of the United States government
Surface acoustic wave (SAW) devices can generate significant heat due to acoustic damping when liquid droplets are placed on them, and this heating (acoustothermal heating) can be used for microscale heating purposes. However, SAW devices are often used in biosensing applications where significant acoustothermal temperature rise can damage the proteins or the biomolecules and destroy the sensor performances. In this paper, we have performed thermal camera-based experiments to study the heating phenomena and how they can be controlled by varying droplet sizes. We found that the temperature rise linearly increases with increasing SAW power whereas it decreases with increasing droplet volume. Hence, a larger liquid volume and lower SAW power can be used in biosensors to avoid significant heating.
more »
« less
Heating of Rayleigh surface acoustic wave devices in 128°YX LiNbO3 and ST X quartz substrates
Heating of surface acoustic wave (SAW) devices can be utilized for micro-heating and in microreactor applications, but is a disadvantage in biosensing. In this contribution, we fabricate SAW devices in 128° YX LiNbO3 and ST X quartz substrates with same physical dimensions, having center frequencies approximately of 96 MHz and 78 MHz, respectively to study heating at several power levels. We demonstrate droplet heating is caused by acoustic wave streaming resulting from the coupling between fluid and solid. A 10 μm water droplet on a 128° YX LiNbO3 device can be heated up by 3.3 °C with 15 dbm power level, whereas, the ST X quartz device is only heated up by 0.7°C. Our work illustrates that the 128° YX LiNbO3 substrate shows great potential for liquid heating applications. The ST quartz substrate is better suited for removal of non-specifically bound (NSB) proteins in biosensing applications, especially if shear horizontal SAWs propagating in the orthogonal direction are utilized for biosensing.
more »
« less
- Award ID(s):
- 1640668
- PAR ID:
- 10050297
- Date Published:
- Journal Name:
- SENSORS, 2017 IEEE
- Page Range / eLocation ID:
- 1 to 3
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Controlled trapping of cells and microorganisms using substrate acoustic waves (SAWs; conventionally termed surface acoustic waves) has proven useful in numerous biological and biomedical applications owing to the label- and contact-free nature of acoustic confinement. However, excessive heating due to vibration damping and other system losses potentially compromises the biocompatibility of the SAW technique. Herein, we investigate the thermal biocompatibility of polydimethylsiloxane (PDMS)-based SAW and glass-based SAW [that supports a bulk acoustic wave (BAW) in the fluid domain] devices operating at different frequencies and applied voltages. First, we use infrared thermography to produce heat maps of regions of interest (ROI) within the aperture of the SAW transducers for PDMS- and glass-based devices. Motile Chlamydomonas reinhardtii algae cells are then used to test the trapping performance and biocompatibility of these devices. At low input power, the PDMS-based SAW system cannot generate a large enough acoustic trapping force to hold swimming C. reinhardtii cells. At high input power, the temperature of this device rises rapidly, damaging (and possibly killing) the cells. The glass-based SAW/BAW hybrid system, on the other hand, can not only trap swimming C. reinhardtii at low input power, but also exhibits better thermal biocompatibility than the PDMS-based SAW system at high input power. Thus, a glass-based SAW/BAW device creates strong acoustic trapping forces in a biocompatible environment, providing a new solution to safely trap active microswimmers for research involving motile cells and microorganisms.more » « less
-
A device incorporating both Rayleigh wave and shear horizontal surface acoustic waves is made on a ST-Quartz substrate. The Rayleigh wave induced microfluidic mixing shows effects on accelerating the binding kinetics of real-time sensing between antibody and antigen, which is measured by phase change from the shear horizontal surface acoustic wave direction on the ST-Quartz. Preliminary results on this device show shortened response time and enhanced phase signal when the binding is accelerated by microfluidic streaming from the Rayleigh wave. The device can be fabricated using a low cost, single step photolithography method and can be combined with a small electronic sensor for data readout, which allows for a variety of surface-based biomarker detections on a portable platform. In this work, detection of Carcinoembryonic antigen (CEA) binding with functionalized capture antibody is studied to show the effects of mass loading amplification due to Rayleigh wave microfluidic streaming.more » « less
-
Acoustic streaming has been widely used in microfluidics to manipulate various micro−/nano-objects. In this work, acoustic streaming activated by interdigital transducers (IDT) immersed in highly viscous oil is studied numerically and experimentally. In particular, we developed a modeling strategy termed the “slip velocity method” that enables a 3D simulation of surface acoustic wave microfluidics in a large domain (4 × 4 × 2 mm 3 ) and at a high frequency (23.9 MHz). The experimental and numerical results both show that on top of the oil, all the acoustic streamlines converge at two horizontal stagnation points above the two symmetric sides of the IDT. At these two stagnation points, water droplets floating on the oil can be trapped. Based on these characteristics of the acoustic streaming field, we designed a surface acoustic wave microfluidic device with an integrated IDT array fabricated on a 128° YX LiNbO 3 substrate to perform programmable, contactless droplet manipulation. By activating IDTs accordingly, the water droplets on the oil can be moved to the corresponding traps. With its excellent capability for manipulating droplets in a highly programmable, controllable manner, our surface acoustic wave microfluidic devices are valuable for on-chip contactless sample handling and chemical reactions.more » « less
-
The evaporation of droplets on surfaces is a ubiquitous phenomenon essential in nature and industrial applications ranging from thermal management of electronics to self-assembly-based fabrication. In this study, water droplet evaporation on a thin quartz substrate is analyzed using an unsteady two-step arbitrary Lagrangian-Eulerian (ALE) moving mesh model, wherein the evaporation process is simulated during the constant contact radius (CCR) and contact angle (CCA) modes. The numerical model considers mass transfer in the gas domain, flow in the liquid and gas domains, and heat transfer in the solid, liquid, and gas domains. Besides, the model also accounts for interfacial force balance, including thermocapillary stresses, to obtain the instantaneous droplet shape. Experiments involving droplet evaporation on unheated quartz substrates agree with model predictions of contact radius, contact angle, and droplet volume. Model results indicating temperature and velocity distribution across an evaporating water droplet show that the lowest temperatures are at the liquid-gas interface, and a single vortex exists for the predominant duration of the droplet's lifetime. The temperature of the unheated substrate is also significantly reduced due to evaporative cooling. The interfacial evaporation flux distribution, which depends on heat transfer across the droplet and advection in the surrounding medium, shows the highest values near the three-phase contact line. In addition, the model also predicts evaporation dynamics when the substrate is heated and exposed to different advection conditions. Generally, higher evaporation rates result from higher substrate heating and advection rates. However, substrate heating and advection in the surrounding gas have minimal effects on the relative durations of CCR and CCA modes for a given receding contact angle. Specifically, in this case, a 40× increase in substrate heating rate or 7.5× increase in gas velocity can only change these relative durations by 3%. This study also highlights the importance of surface wettability, which affects evaporation dynamics for all the conditions explored by the numerical model.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/ICSENS.2017.8234389
