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:
Date of submission:
Author:
30 April 2013
15 May 2013
Prof. Electra Gizeli
DELIVERABLE SUMMARY SHEET
Project Number
Project Acronym
Title
Deliverable
Partners Contributed
Authors
Classification
: 317742
: LOVE-FOOD
: LOVE Wave Fully Integrated Lab-on-Chip Platform for FOOD-Pathogen
Detection
: D2.1
: FORTH, Senseor
: Dr. George Papadakis, Dr Jean-Michel Friedt, Prof. Electra Gizeli
: PU
DOCUMENT HISTORY
Date
Version
22/04/2013
10/05/2013
12/05/2013
14/052013
1
2
3
4
15/05/2013
5
Description
Text submitted by JM Friedt
Text added by Dr G. Papadakis
Revised manuscript by Coordinator
Additional Annex provided by JM Friedt
Coordinator approves and submits final
version
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Table of Contents
Executive Summary………………………………………………………………………………………………..….…….....4
Main text…………………………………………………………………………………………………………………………………….....5
1. 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
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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 18 functional 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 photolithographic techniques 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.
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Main Text
1. 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 is presented 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)
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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).
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(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.
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(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.
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Conclusions
We have evaluated the performance of several Love wave acoustic 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 155 MHz 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.
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Annex I
Table 1: Summary of the evaluation of the tested acoustic devices operating at different frequencies
covered with various waveguides
Device
Side of Amplitude (dB),
device
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%)
125 (2%
PMMA)
-29.167 (2%)
left
-44.487
No signal
Ampl: 1,257 db
Phase: 16,42 deg
(PMMA 2%)
Ampl: 1,515 db
Phase: 20,292 deg
(NO PMMA)
No signal
(PMMA 8%)
-35.959 (8%)
-44.042 (2%)
3
(310
MHz)
right
-56.445
No signal
-27.981 (2%)
135 (2%
PMMA)
-
-31.834 (14%)
left
-52.017
No signal
-27.692 (2%)
Ampl: 1,135 db
Phase: 10,228 deg
(PMMA 2%)
-27.520 (14%)
Ampl: 0,581 db
Phase: 7,694 deg
(NO PMMA)
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%)
7
(155
No signal (17%)
-
Ampl: - Phase: (signal is lost after
applying flow-cell)
(PMMA 14%)
-
-
-
240 (8%
PMMA)
Ampl: 0,947 db
Phase: 11,928 deg
(PMMA 8%)
left
-29.851
No signal
-22.540 (8%)
No signal (17%)
-
right
-32.424
-27.978
-
Not sensitive
(no photoresist)
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MHz)
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)
9
(155
MHz)
10
(155
MHz)
left
-
-27.121
-
right
-
-43.073
-
left
-
-37.671
-
right
-
-25.418
-
left
-
-22.704
-
Ampl: 1,413 db
Phase: 30,194 deg
(photoresist)
Ampl: 1,672 db
Phase: 30,955 deg
(photoresist)
1000
Photoresist
Ampl: 1,672 db
Phase: 21,756 deg
(photoresist)
-
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%)
-
right
-59.345
-57.048
-57.236 (20%)
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-
1210
(PMMA)
-
-
13
(35
MHz)
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)
14
(105
MHz)
right
-66.618
-58.018
--57.164 (25%)
left
-65.051
-57.787
-55.960 (25%)
Ampl: 0,03 db
Phase: 0,511 deg
(PMMA 25%)
right
-56.984
-
no double peak was
observed
-
left
-65.096
-
no double peak was
observed
-
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2015
(PMMA)
Not sensitive
(PMMA 25%)