A SU-8 liquid cell for surface acoustic wave biosensors (original) (raw)
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An SU-8 liquid cell for surface acoustic wave biosensors
MEMS, MOEMS, and Micromachining, 2004
One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 µm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.
Design and Use of Wafer Level Fluidic Packaging for Surface Acoustic Wave Sensors
2007 IEEE International Frequency Control Symposium Joint with the 21st European Frequency and Time Forum, 2007
We demonstrate the propagation of a Love mode acoustic wave in a thin SU8 epoxy layer coating a AT-cut quartz substrate: the resulting insertion losses are observed in the -35 to -40 dB range. We demonstrate the packaging of this device in a SU8 microfluidic system preventing liquids from covering the interdigitated transducer while defining the chemical reaction area in the region between the interdigitated transducer. We demonstrate the ability to chemically functionnalize the SU8 layer with amine-ended groups. Finally, a time-resolved adsorption of small (600 daltons) organometallic molecules is presented for illustrating the detection sensitivity and selectivity of the resulting sensor working with analytes in acqueous solutions.
Integration of a surface acoustic wave biosensor in a microfluidic polymer chip
Biosensors and Bioelectronics, 2006
SAW devices based on horizontally polarized surface shear waves (HPSSW) enable label-free, sensitive and cost-effective detection of biomolecules in real time. It is known that small sampling volumes with low inner surface areas and minimal mechanical stress arising from sealing elements of miniaturized sampling chambers are important in this field. Here, we present a new approach to integrate SAW devices with sampling chamber. The sensor device is encapsulated within a polymer chip containing fluid channel and contact points for fluidic and electric connections. The chip volume is only 0.9 l. The polymeric encapsulation was performed tailor-made by Rapid Micro Product Development 3Dimensional Chip-Size-Packaging (RMPD ® 3D-CSP), a 3D photopolymerisation process. The polymer housing serves as tight and durable package for HPSSW biosensors and allows the use of the complete chips as disposables. Preliminary experiments with these microfluidic chips are shown to characterise the performance for their future applications as generic bioanalytical micro devices.
IntechOpen eBooks, 2022
There has been a renewed interest in the development of surface acoustic wave (SAW) biosensors because they hold great promise for opening new frontiers in biology and medicine. The promise of SAW technology is grounded in the advantages SAW devices hold over traditional laboratory techniques used in biological and medical laboratories. These advantages include having smaller sizes to allow greater portability, using smaller sample volumes, requiring lower power requirements, the ability to integrate them into microfluidic platforms, and their compatibility with smart devices such as smartphones. The devices offer high sensitivity and can be designed to allow microfluidic interfacing. Other major advantages of SAW-based technologies include the fact that they can be operated remotely in harsh conditions without the need for an AC power supply. Their compatibility with lab-on-a-chip systems allows the creation of fully integrated devices with the ability to isolate the sample from the operator. In this mini-review, we will discuss SAW devices and their ability to enable a variety of applications in Biology and Medicine. The operating principles of the SAW biosensors will be discussed along with some technological trends and developments.
A High-performance Lab-on-a-chip Liquid Sensor Employing Surface Acoustic Wave Resonance: Part II
Journal of Micromechanics and Microengineering
We recently introduced an in-liquid sensing concept based on surface acoustic resonance (SAR) in a lab-on-a-chip resonant device with one electrical port. The 185 MHz one-port SAR sensor has a sensitivity comparable to other SAW in-liquid sensors, while offering a high quality factor (Q) in water, low impedance, and fairly low susceptibility to viscous damping. In this work, we present significant design and performance enhancements of the original sensor presented in part I. A novel "lateral energy confinement (LEC)" design is introduced, where the spatially varying reflectivity of the SAW reflectors enables strong SAW localization inside the sensing domain at resonance. An improvement in mass-sensitivity greater than 100% at resonance is achieved, while the measurement noise stays below 0.5 ppm. Sensing performance was evaluated through real-time measurements of the binding of 40 nm neutravidin-coated SiO2 nanoparticles to a biotin-labeled lipid bilayer. Two complementary sensing parameters are studied, the shift of resonance frequency and the shift of conductance magnitude at resonance. I.
Conformable surface acoustic wave biosensor for E-coli fabricated on PEN plastic film
Biosensors and Bioelectronics, 2020
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Surface Modification on Acoustic Wave Biosensors for Enhanced Specificity
Sensors, 2012
Changes in mass loading on the surface of acoustic biosensors result in output frequency shifts which provide precise measurements of analytes. Therefore, to detect a particular biomarker, the sensor delay path must be judiciously designed to maximize sensitivity and specificity. B-cell lymphoma 2 protein (Bcl-2) found in urine is under investigation as a biomarker for non-invasive early detection of ovarian cancer. In this study, surface chemistry and biofunctionalization approaches were evaluated for their effectiveness in presenting antibodies for Bcl-2 capture while minimizing non-specific protein adsorption. The optimal combination of sequentially adsorbing protein A/G, anti-Bcl-2 IgG and Pluronic F127 onto a hydrophobic surface provided the greatest signal-to-noise ratio and enabled the reliable detection of Bcl-2 concentrations below that previously identified for early stage ovarian cancer as characterized by a modified ELISA method. Finally, the optimal surface modification was applied to a prototype acoustic device and the frequency shift for a range of Bcl-2 concentration was quantified to demonstrate the effectiveness in surface acoustic wave (SAW)-based detection applications. The surface functionalization approaches demonstrated here to specifically and sensitively detect Bcl-2 in a working ultrasonic MEMS biosensor prototype can easily be modified to detect additional biomarkers and enhance other acoustic biosensors.
Surface Acoustic Wave Studies for Chemical and Biological Sensors
Springer eBooks, 2007
Surface Acoustic Waves on piezoelectric substrates are very sensitive to any external modulation of the mechanical and/or electrical boundary conditions at the surface on which they propagate. This makes them a perfect tool for sensor applications. In this manuscript, we demonstrate that a sophisticated transducer design allows for a spatial resolution of the interaction of SAW and local modulation of the electrical and mechanical boundary condition. If such local disturbances of parts of the functionalized sample surface are due to a chemical or optical interaction, a single chip with many different 'pixels' can act as a novel type of sensor.
Immunosensing with surface acoustic wave sensors
Sensors and Actuators A: Physical, 1997
In this paper we present the utilization of horizontally polarized surface acoustic waves for immunosensing in liquids. We have used a du aldelay-line device on an LiTaO~ substrate working at 345 MHz to detect immunoglobulins of type G in phosphate buffer. The measurements are performed either using a 'droplet technique' with small amounts (5 tzl) of liquid, or in a flow-through cell. From the experimental results we derive a sensitivity of 112.5 kHz (ng mm-2)-~ and a detection limit of 35 pg for the absolute mass. We find a quadratic frequency dependence of the sensor signal, indicating a mass-loading effect.