Presentation by
Bello Hamza Abdullahi
Table of contents
 Introduction.
 Suspended microchannel Resonator(SMR).
 Beam Model.
 SMR With Integrated Piezoresistive Readout.
 Fabrication Of SMR.
 Performance Factors.
 Advantages.
 Applications.
Introduction
 There are three commonly used devices in detecting
bio-molecules, these are;
 microcantilever-based biosensor.
 Surface Plasmon Resonance (SPR) sensor and,
 Quartz Crystal Microbalance (QCM) sensor.
 For micro-cantilever-based biosensors, there are two
working principles developed for the biodetection,
namely, the static mode and the dynamic mode.
Suspended Micro-channel
Resonator(SMR)
 SMR is a biosensor that falls under micro-cantilever
based dynamic mode biosensor.
 This is a hollow micro-cantilever that vibrate with a
certain resonance frequency. It resonates at a
frequency proportional to its total mass⁽²⁾.
 This works base on the reduction of resonance
frequency of the hollow microcantilever induced by
molecular adhesion, if an analyte flow through the
hollow cantilever.
SMR
 Since SMR is a cantilever it should have the following;
 Since the tip end, is freely suspended it can easily
vibrate.
 There is low or even no effect of vibration at the fixed
end.
 It resonates at a frequency proportional to its total
mass. Therefore change in mass affect the resonance
frequency.
 The vibration intensity reduced as you move from the
tip end to the fixed end.
SMR
 Particles are weighed in real-time with the suspended
micro-channel resonator (SMR) as they flow through a
hollow cantilever.
 The micro-channel resonant frequency is determined
by the difference in mass of the particle with respect to
that of the displaced fluid.
 Thus, the particle's density is determined by
measuring its mass in two fluids of different densities.
Beam Model Of SMR
 As the fluid flows inside the SMR, we could study how
the relevant properties of the fluid affect its resonant
frequency.
 Derivation of the dynamic theory of the SMR is mainly
separated into two parts, namely:
 A structure element and,
 fluid element.
Beam model of SMR
 The structural parts depends on the following
parameters;
 The cross sectional area of the internal rectangle
tube,(A); young modulus ,(E); Moment of inertia, (I)
 Mass per unit length of the empty rectangle tube,(m)
 Longitudinal tension applied on the structure
element,(T)
Beam Model of SMR
 Transverse shear force applied on the structure
element(Q),
 Bending moment applied on the structure
element(M),
 shear stress on the internal surface of the rectangle
tube(q),
 Inner perimeter of the rectangle tube(S),
Beam Model of SMR
 For the fluids, depends on:
 The flow pressure(P),
 Density(Ƿ),
 viscosity(μ),
 Shear stress induced by the viscosity(δ) and,
 The transverse force per unit length between tube wall
and fluid(F).
 Following the D’Alembert’s principle of dynamic
equilibrium⁽¹⁾, the equation of motion for the SMR is
given in the next slide.
A Sketch of the 1-D beam
model.
where v(x, t) is the deflection of the beam. U is the average
flow velocity. L,B and H is the length, width, and height of the
beam, respectively.
Beam Model of SMR
Beam Model of SMR
Then Eq. (2) can be rewritten as
The solution of the above equation can be
represented by
Beam Model of SMR
 where фn`s are the normal modes of the beam without
viscosity (i.e.χ = 0),
 κ n`s are the expansion coefficients, and
 ω is the dimensionless circular frequency,
 where f is the frequency.
 By orthogonality of ф n(ξ ), one can obtain the
following equation from (4) and (5): See next slide.
Beam Model of SMR
 where the coefficient matrices [A] to [E] are defined by
Beam Model of SMR
 To obtain nontrivial solutions, the determinant of
coefficient matrix must be zero, i.e.,
 From the above equation, one can determine the
resonant frequencies of the SMR as:
SMR with Integrated Piezoresistive
Readout
 So far, the frequency measurement of our device has
relied on measuring the deflection of a laser beam that
is focused onto the tip of the resonator.
 The optics used in our lab do not scale favorably for
large arrays and are not suitable for point of-use
applications.
 On the contrary, Suspended microchannel resonators
with integrated (I.e piezoresistive) readout can
measure the mass density of solutions with high
precision.
Basic Operations of piezoresistive
SMR
 Readout of the resistance change is amplified through a
Wheatstone bridge.
 Potentiometers are incorporated in order to balance the
amplifier as well as compensate for capacitive coupling of
the electrostatic drive signal.
 Figure 1 shows the frequency response which corresponds
to superposition of the signal from the resistor and the
drive signal feed through.
 Measurements of resistance change as the entire device is
heated in a convection oven suggest that a reasonable bias
voltage of 1V on the bridge will result in biocompatible
temperatures of less than 40⁰C.
Fabrication of SMR

Hard fabrication techniques used to mass-produce
silicon portion of device.
 Usually the material use in this fabrication is silicon.
 Device is fabricated in two components, then glass
frit-bonding is used.
 Silicon cantilever/functional portion
 Pyrex capping portion, chosen for transparency .
Silicon Fabrication
RIE to form channel .
b.
Structural material, low-stress SixNy, placed then
sacrificial layer of poly-Si (LPCVP). Removal of poly-Si
performed by chemical-mechanical planarization .
c.
Another layer of SixNy deposited, and poly-Si dissolved.
d.
Chromium placed by ion beam deposition (provides
reflectivity).
e. Chromium and SixNy removed where fluid is in contact
with device.
f.
Bulk micromachining with TMAH.
a.
Pyrex Fabrication
•
•
•
•
•
•
Silicon mask bound to mask and patterned by
DRIE.
Deep glass etching performed.
Mask patterned by DRIE again.
Gold film deposited.
Gold film patterned.
Glass fritting printed onto Pyrex.
Performance factors
 Selectivity
 Sensitivity
 Accuracy
 Response time
 Recovery time
 Lifetime
 Reliability
 Resolution
 Precision
Advantages of SMR
 Ability to measure mass density with a resolution up to
10⁻⁴g/mL.
 High Precision frequency detection has enabled the
suspended micro-channel resonator (SMR) to weigh
single living cells, single nano-particles, and adsorbed
protein layers in fluid.(I.e Weighing particles with
femtogram precision.)
Applications
 SMR is used as:
 Bio-molecular detector.
 Monitoring cells growth.
Biomolecular Detection
Bio-molecular Detection
 Since the surface area to volume ratio of the suspended
micro-channel resonator (SMR) is very large, surface
adsorption is an effective mechanism for biomolecular mass sensing.
 The exact mass of an absorbed layer can be quantified
by measuring the difference in resonance frequency
before, during (i.e. in real time) and after each
injection.
 At the surface of the hollow site, biological recognition
agents, can be use to absorbed the analyte.
Biomolecular Detection
Biomolecular Detection
 Biological systemsthe major selective elements
 They must attach themselves to one particular
substrate, but not to others.
 They comprises of the following;
 Enzymes,
 Antibodies,
Nucleic acids and,
Receptors.
Monitoring Cell Growth
 G1-synchronized cells have a negative buoyant mass




(positive frequency shift).
This cell passes through the channel floating on the
surface of the fluid.
This undergoes a circulation through the channel.
The cells entering S phase at a later time point have a
positive buoyant mass (negative frequency shift).
This implies that the cell increases in size since it sink
in the fluid.(I.e implies cell growth)
Monitoring Cell Growth
Monitoring Cell Growth
References
1.
2.
3.
4.
Beam model and three dimensional numerical simulations on suspended
microchannel resonators Kuan-Rong Huang, Jeng-Shian Chang, Sheng
D. Chao, and Kuang-Chong Wu
Proc Natl Acad Sci U S A. 2010 January 19; 107(3): 999–1004.
Published online 2009 December 23. doi: 10.1073/pnas.0901851107
PMCID: PMC2824314 Engineering, Cell Biology.
Suspended microchannel resonator for improved PSA monitoring. Luke
Albares, griffin, Andy guan, Dillon Achendal, Alex Shepler
SUSPENDED MICROCHANNEL RESONATORS WITH
INTEGRATED ELECTRONIC READOUT FOR BIOMOLECULAR
AND SINGLE CELL ANALYSIS
R. Chunara1, T.P. Burg2, K. Payer3, P. Dextras2, S.R. Manalis2
1Harvard-MIT Division of Health Sciences and Technology, USA
2Department of Biological Engineering, MIT, USA
3Microsystems Technology Laboratories, MIT, USA