Love Wave Fully Integrated Lab-on-chip Platform
for Food Pathogen Detection - LOVE-FOOD
(Contract No 317742 – Starting Date: 1 September 2012)
Deliverable 2.1
Report on fabricated SAW and resonator-based Love wave devices
Due date: / 30 April 2013Date of submission: / 15 May 2013
Author: / Prof. Electra Gizeli
DELIVERABLE SUMMARY SHEET
Project Number / : / 317742Project Acronym / : / LOVE-FOOD
Title / : / LOVE Wave Fully Integrated Lab-on-Chip Platform for FOOD-Pathogen Detection
Deliverable / : / D2.1
Partners Contributed / : / FORTH, Senseor
Authors / : / Dr. George Papadakis, Dr Jean-Michel Friedt, Prof. Electra Gizeli
Classification / : / PU
DOCUMENT HISTORY
Date / Version / Description22/04/2013 / 1 / Text submitted by JM Friedt
10/05/2013 / 2 / Text added by Dr G. Papadakis
12/05/2013 / 3 / Revised manuscript by Coordinator
14/052013 / 4 / Additional Annex provided by JM Friedt
15/05/2013 / 5 / Coordinator approves and submits final version
Table of Contents
Executive Summary………………………………………………………………………………………………..….…….....4
Main text…………………………………………………………………………………………………………………………………….....5
- Introduction...... 5
A Design, fabrication and RF testing of individual SAW devices operating at various frequencies……...... 5
B Performance evaluation of SAW devices to liquid sensing…………………………………………………………………...6
C Acoustic measuring electronics……………………………………………………………………………………………………………..8
D Theoretical modeling………………………………………………………………………………………………………………………..……8
Conclusions…………………………………………………………………………………………………………………………………..…9
Annex I………………………………………………………………………………………………………………………………………………………10
Annex II……………………………………………………………………………………………………………………………………………………..13
Executive Summary
Description of work
This deliverable is related to the design and fabrication of SAW and resonator Love wave devices. Originally, it was proposed to fabricate devices operating at a range of frequencies from few tens to few hundred of MHz.In the first 8 months of work,22 SAW devices operating at 5 different frequencies were designed, fabricated and evaluated for acoustic signal quality in a Love wave configuration, using 2 different waveguides. Eighteen out of the 22 devices checked were functional providing a good acoustic signal. Resonators were also produced; however, due to defects no performed evaluation was carried out.Each of the 18functional SAW devices was evaluated based on the acoustic signal response after liquid loading followed by mass loading during protein adsorption on the device surface.In addition, rigorous theoretical modeling was carried out in order to define the design parameters that would affect mass sensitivity of the Love SAW and resonator systems.
Materials and methods
For this deliverable, device fabrication was carried out using standard photolithographictechniques while quartz was the piezoelectric material of choice. Wet chemistry experiments employed standard biological reagents, such as commercially available neutravidin protein and home-PCR produced ds DNA. Theoretical calculations were based on specifically-developed software.
Conclusions
The most sensitive devices were the ones operating at 155MHz covered with photoresist as a waveguide layer.This was in agreement with theoretical calculations that showed superior performance of the Love wave geometry with a polymer rather than a silica waveguide layer. The above device geometry, tested with a Network analyzer, performed equally well to the commercial acoustic system employing a Quartz Crystal Microbalance at 35 MHz (Q-Sense). SAW delay lines operating at higher frequencies, as well as Love wave resonators, will be fabricated and tested in the next few months and presented in D2.2.
Main Text
- Introduction
Work described in this report covers the first 8 months of WP1 and deals with the design and fabrication of two types of SAW-based Love wave devices (delay lines and resonators) operating at various frequencies. The most promising chips after careful evaluation will be used in an array format integrated with microfluidics for the development of a LOC platform. For this reason, all functional devices were tested towards their ability to detect protein and DNA binding to the device surface.In addition, this deliverable presents preliminary data towards the design, construction and implementation of the electronics required to collect and present the acoustic data originating from the LOC. Finally, a rigorous theoretical model was developed for the evaluation of mass sensitivity of each type of sensor (SAW delay line and resonator) as a function of several design parameters.
A.Design, fabrication and RF testing of individual SAW devices operating at various frequencies
SENSEOR provided the FORTH partner with various types of SAW delay lines (fig. 1) operating at different frequencies. In summary, 22 devices operating at 5 different frequencies (35, 105, 155, 310 and 450 MHz) were initially evaluated for acoustic signal quality using 2 different waveguides; PMMA and photoresist. The PMMA percentages used for the evaluation ranged from 0 up to 20%. PMMA with increased roughness was also used in an attempt to increase the surface area to facilitate immobilization procedures. 18 out of the 22 devices checked were functional providing a good acoustic signal. Fig. 2 shows the spectra of two different devices one functional (a) and a non-functional one (b). A full list of the results of the initial evaluation ispresented in Annex I (Table 1). A summary of the work done in Task 2.1 is schematically represented in fig. 3.
Fig. 1: Schematic representation of a SAW delay line.
(a) (b)
Fig. 2: Acoustic spectra from SAW delay lines. (a) Acoustic signal (amplitude and phase) in air of a fully functional device. (b)
Fig. 3: Summary of the work done in Task 2.1
An important observation regarding the construction of SAW delay lines was the fact that the metal pads were found to be easily scratched by the contact pins. This defect should be avoided in the next production batch by changing the metal pad composition.
According to this task, resonators are also expected to be produced and evaluated in a similar way. So far, the first batch of resonators displayed defects; i.e. higher than expected insertion losses and large temperature drifts. Another production run is scheduled to be completed by mid May.
B.Performance evaluation of SAW devices to liquid sensing
Functional SAW delay lines were further evaluated towards their sensitivity in liquid environment in 4 stages (fig. 4). At first, each of the 18 devices was evaluated based on the acoustic signal after liquid loading followed by monitoring of its response to mass loading (during neutravidin protein adsorption). The most sensitive devices (fig. 5) were then used for immobilizing biotinylated DNA fragments with or without nucleic acids column purification.
Fig. 4: Performance evaluation stages of SAW delay lines.
FORTH partner produced 9 DNA molecules with lengths ranging from 30 to 1724 bp which were immobilized on a neutravidin covered surface and the acoustic ratio (Δphase/Δamplitude) of each of the DNA was measured. The experiments were carried out using the 155 MHz (with photoresist as a waveguide) delay line constructed by SENSEOR and an Agilent Network Analyzer. As a reference, the same experiments were performed using the QCM-D E4 system from Q-Sense. The produced acoustic ratio curves (fig. 6) from the two systems were found to be almost identical which illustrates that the produced delay line (SENSEOR) is comparable in performance to an established commercial chip from Q-Sense.
As a final stage of evaluation, unpurified PCR products were loaded on the same device (155MHz with photoresist) in order to simulate, in part, the conditions under which the final LOC platform will be operating. The results showed that discrimination among different DNA molecules is possible even without prior purification (fig. 7).
(a)
(b)
Fig. 5: (a) Real time measurements of phase and amplitude during protein adsorption. (b) Phase (deg) and amplitude (dB) measurement results for neutravidin adsorption using the devices under evaluation.
Fig. 6: Acoustic ratio curves from 9 DNA molecules (30, 157, 297, 422, 524, 689, 1011, 1294, 1724 bp) produced by PCR and purified with a nucleic acids purification column. The measurements were performed both in SAW and QCM chips.
The above promising results were produced by using the 155 MHz with photoresist waveguide device. The same experiments could not be reproduced by using devices operating at 450 MHz and 310 MHz. Furthermore, the 35 and 105 MHz devices could not be operated at all in liquid environment. The reasons behind these observations are under investigation. Improving the performance of the 155 MHz will also be attempted by changing the thickness of the waveguide layers.
(a) (b)
Fig. 7: (a) Real time measurements of phase and amplitude changes upon sequential loading of 3 different unpurified PCR products corresponding to 3 different pathogens. (b) Acoustic ratios are indicative of the different pathogen types.
C. Acoustic measuring electronics
Precise monitoring of the SAW delay line and resonator response requires the development of dedicated RF electronics. SENSEOR provided the FORTH partner with a first version of an electronics system capable of collecting data from 8 different channels. This system was evaluated by repeating the unpurified PCR measurements on exactly the same device (155MHz+photoresist) and collecting the data using the software developed by SENSEOR. As depicted in fig. 8 the real time measurements derived from the SENSEOR electronics unit are much more noisy and inferior to the corresponding results provided by the Agilent analyzer (fig. 7a). It should be noted that this was only a first version which is still under development and therefore, significant improvement of its operation is expected in the future.
Fig. 8: Real time measurements of phase and amplitude changes upon sequential loading of 3 different unpurified PCR products corresponding to 3 different pathogens.
D.Theoretical modeling
The physical quantities under investigation are the acoustic wave velocity and losses. The most basic approach to velocity measurement is a time of flight measurement, or its implementation in terms of continuous wave with a phase measurement between the input signal and the output signal propagating through the acoustic device sensing area. A detailed presentation of the model, investigated parameters and results is given in Annex II.
Conclusions
We have evaluated the performance of several Love waveacoustic devices. We followed a 4-stage procedure in order to conclude which will be the best device to incorporate into the final platform in terms of sensitivity, reproducibility and overall performance in comparison to an established commercial chip (as for example Q-Sense).
Our results indicate that the SAW chips operating at 155MHz and covered with a photoresist waveguide are the most sensitive in terms of mass detection and perform well under conditions similar to those that will be applied to the final LOC platform; in addition, this device gave comparable results to the Q-Sense commercially available system. Further optimization of the particular device type regarding the metal pad compositions and the waveguide thickness are required to extend its life cycle, sensitivity and overall performance. Regarding devices operating at higher frequencies, initial results were not encouraging, since they gave either a poor acoustic signal of high losses, or resulted in low mass sensitivity. However, further optimization of the SAW delay line geometry will be carried out and new devices will be fabricated in the next few months, as well as resonators.
Regarding the electronics unit operation we found out that the monitored acoustic signal is characterized by high noise levels and inferior quality compared to a commercial network analyzer, therefore, significant improvement of its performance is required. However the deliverable of the device instrumentation is not due until M30, therefore we feel that there is enough time to build the instrument well within the project timeframe.
Theoretical simulations were in good agreement with experimental data, where a polymer waveguide layer was found to be superior to a silica one. Theoretical data will also be used to optimize design parameters for the fabrication of a second generation of acoustic resonators.
Annex I
Table 1: Summary of the evaluation of the tested acoustic devices operating at different frequencies covered with various waveguides
Device / Side of device / Amplitude (dB), no PMMA,no photoresist / Amplitude (dB), with
photoresist / Amplitude (dB),
with PMMA (%) / Average
thickness
(nm) / Signal obtained during Neutravidin binding (200 μg/ml)
1
(450
MHz) / right / No signal / No signal / - / - / -
left / No signal / No signal / - / -
2
(450
MHz) / right / -58.792 / No signal / -46.080 (8%)
-29.167 (2%) / 125 (2% PMMA) / Ampl: 1,257 db
Phase: 16,42 deg
(PMMA 2%)
Ampl: 1,515 db
Phase: 20,292 deg
(NO PMMA)
left / -44.487 / No signal / -35.959 (8%)
-44.042 (2%) / No signal
(PMMA 8%)
3
(310
MHz) / right / -56.445 / No signal / -27.981 (2%)
-31.834 (14%) / 135 (2% PMMA) / -
left / -52.017 / No signal / -27.692 (2%)
-27.520 (14%) / Ampl: 1,135 db
Phase: 10,228 deg
(PMMA 2%)
Ampl: 0,581 db
Phase: 7,694 deg
(NO PMMA)
Ampl: - Phase: -
(signal is lost after applying flow-cell)
(PMMA 14%)
4
(310
MHz) / right / -32.140 / No signal / -29.932 (2%) / - / -
left / -56.156 / No signal / -27.622 (2%) / -
5
(310
MHz) / right / -29.938 / No signal / -22.241 (8%) / - / -
left / -32.326 / No signal / -30.995 (8%) / -
6
(310
MHz) / right / -31.660 / No signal / -21.026 (8%)
No signal (17%) / 240 (8% PMMA) / Ampl: 0,947 db
Phase: 11,928 deg
(PMMA 8%)
left / -29.851 / No signal / -22.540 (8%)
No signal (17%) / -
7
(155
MHz) / right / -32.424 / -27.978 / - / Not sensitive
(no photoresist)
left / -75.342 / -22.460 / - / -
8
(155
MHz) / right / - / -22.283 / - / Ampl: 1,057 db
Phase: 31,143 deg
(photoresist)
Ampl: 0,424 db
Phase: 38,177 deg
(photoresist)
left / - / -27.121 / - / Ampl: 1,413 db
Phase: 30,194 deg
(photoresist)
9
(155
MHz) / right / - / -43.073 / - / Ampl: 1,672 db
Phase: 30,955 deg
(photoresist)
left / - / -37.671 / - / Ampl: 1,672 db
Phase: 21,756 deg
(photoresist)
10
(155
MHz) / right / - / -25.418 / - / 1000
Photoresist / -
left / - / -22.704 / - / Ampl: 1,328 db
Phase: 29,384 deg
(with photoresist)
Ampl: 1,271 db
Phase: 32,008 deg
(with photoresist, after plasma)
11
(35
MHz) / right / -78.455 / -57.766 / -67.387 (17%) / -
left / -60.342 / -56.552 / -58.475 (17%) / Not sensitive
(with photoresist)
11
(105
MHz) / right / -76.046 / - / -54. 595 (17%) / -
left / -58.053 / - / -45. 420 (17%) / Ampl: 0,134 db
Phase: 3,135 deg
(PMMA 17%)
12
(35
MHz) / right / -(scratched) / -57.617 / -
(scratched) / - / -
left / -60.825 / -69.811 / -84.799 (20%) / -
12
(105
MHz) / right / -(scratched) / - / -
(scratched) / -
left / -58.498 / - / -74. 287 (20%) / -
13
(35
MHz) / right / -59.345 / -57.048 / -57.236 (20%) / 1210
(PMMA) / -
left / -59.224 / -56.822 / -57.511 (20%) / a) Not sensitive
(PMMA 20%)
b) Not sensitive
(NO PMMA)
13
(105
MHz) / right / -57.454 / - / -43.364 (20%) / -
left / -56.426 / - / -43.639 (20%) / a) Ampl: 0,284 db
Phase: 4,132 deg
(PMMA 20%)
b) Ampl: -
Phase: 0,893 deg
(NO PMMA)
14
(35
MHz) / right / -66.618 / -58.018 / --57.164 (25%) / 2015 (PMMA) / Not sensitive
(PMMA 25%)
left / -65.051 / -57.787 / -55.960 (25%) / Ampl: 0,03 db
Phase: 0,511 deg
(PMMA 25%)
14
(105
MHz) / right / -56.984 / - / no double peak was observed / -
left / -65.096 / - / no double peak was observed / -
FP7-ICT-2011.3.2 – Contract No 317742 – Deliverable 9.6
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