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DESIGN OF MEMS BASED MICROCANTILEVER FOR
TUBERCULOSIS DETECTION
Saranya R 1
, Saranya K 1
, Ceemati D 1
, Chandra Devi K 1
, Meenakshi Sundaram N 1
1
PSG College of Technology, Department of Biomedical Engineering, Peelamedu, Coimbatore-641 004.
Introduction: Tuberculosis is caused by a bacterium
called Mycobacterium tuberculosis. The fusion protein,
ESAT-6/CFP-10 is secreted by the extended region of
RDX- 1 which encodes ESX-1, a novel protein secretion
system and known to contribute to virulence and
pathogenicity in the host. The most prominent cantilever
type of detection is preferred (figure 1). The objective of
the study was to select the best suited cantilever for
tuberculosis detection.
Computational Models: The three dimensional
geometry of the Cantilever was simulated using COMSOL
Multiphysics 4.3b software (figure 2).The Stoney's formula,
which relates cantilever end deflection 隆 to applied stress 
given by:
--- (1)
Where  is Poisson's ratio,
E is Young's modulus,
L is the beam length and
t is the cantilever thickness
The total force being applied to the cantilever is much more
related to the number of analyte molecules attaching to the
cantilever. The resonance frequency (f) on a cantilever
working in dynamic mode is given by:
--- (2)
Where k is the spring constant,
meff  is the effective or dynamic mass.
Results: The Stationary and Eigen frequency
studies are performed. The simulated results of the
Cantilever structures are given in figures (3) and (4).
The lowering of the resonant frequency is attributed
due to the increase in the mass of analyte over the
thiolated gold surface.
Cantilever
type
Displacement
(袖m)
Eigen
Frequency
(Hz)
Triangular
shape
1.0023*10-13
9.86225
Pi- shape 3.9693*10-21
1.8115*107
Rectangular
shape
9.3887*10-9
4.5078*106
Conclusions: The Eigen frequency and the maximum
displacement were observed for rectangular shaped cantilever
sensor. The sensor is highly sensitive since it can detect even
attomolar concentration of the analyte molecules. For an input
mass of 50 ESX-1 antigens, a maximum displacement of
9.3887*10-19
was observed (figure 5). Thus, a highly sensitive
and selective sensor based on cantilever is simulated using
COMSOL Multiphysics 4.3b.
References:
1.Hemmati M, Expression and Purification of
Recombinant Mycobacterium Tuberculosis Diagnosis
Antigens, ESAT-6, CFP-10, and ESAT-6/CFP-10, and Their
Potential Use in the Diagnosis and Detection of
Tuberculosis, Iranian Red Crescent Medical Journal, Vol.
13, No.8, Pages 558-565,(2011).
2.Danica Helb, Rapid Detection of Mycobacterium
tuberculosis and Rifampin Resistance by Use of On-
Demand Near Patient Technology , Journal of Clinical
Microbiology,Vol. 48, No. 1, Pages. 229237, (2010).
Figure 3. Simulated Results of the Proposed Cantilevers
Figure 5. Displacement Vs Input force for different types of
Cantilever structures
Figure 1. Deflection of the Cantilever upon selective binding
Figure 2: Proposed Geometry of the Cantilever Structures
Figure 3 & 4. Simulation results of the different types of Cantilever

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  • 1. DESIGN OF MEMS BASED MICROCANTILEVER FOR TUBERCULOSIS DETECTION Saranya R 1 , Saranya K 1 , Ceemati D 1 , Chandra Devi K 1 , Meenakshi Sundaram N 1 1 PSG College of Technology, Department of Biomedical Engineering, Peelamedu, Coimbatore-641 004. Introduction: Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis. The fusion protein, ESAT-6/CFP-10 is secreted by the extended region of RDX- 1 which encodes ESX-1, a novel protein secretion system and known to contribute to virulence and pathogenicity in the host. The most prominent cantilever type of detection is preferred (figure 1). The objective of the study was to select the best suited cantilever for tuberculosis detection. Computational Models: The three dimensional geometry of the Cantilever was simulated using COMSOL Multiphysics 4.3b software (figure 2).The Stoney's formula, which relates cantilever end deflection 隆 to applied stress given by: --- (1) Where is Poisson's ratio, E is Young's modulus, L is the beam length and t is the cantilever thickness The total force being applied to the cantilever is much more related to the number of analyte molecules attaching to the cantilever. The resonance frequency (f) on a cantilever working in dynamic mode is given by: --- (2) Where k is the spring constant, meff is the effective or dynamic mass. Results: The Stationary and Eigen frequency studies are performed. The simulated results of the Cantilever structures are given in figures (3) and (4). The lowering of the resonant frequency is attributed due to the increase in the mass of analyte over the thiolated gold surface. Cantilever type Displacement (袖m) Eigen Frequency (Hz) Triangular shape 1.0023*10-13 9.86225 Pi- shape 3.9693*10-21 1.8115*107 Rectangular shape 9.3887*10-9 4.5078*106 Conclusions: The Eigen frequency and the maximum displacement were observed for rectangular shaped cantilever sensor. The sensor is highly sensitive since it can detect even attomolar concentration of the analyte molecules. For an input mass of 50 ESX-1 antigens, a maximum displacement of 9.3887*10-19 was observed (figure 5). Thus, a highly sensitive and selective sensor based on cantilever is simulated using COMSOL Multiphysics 4.3b. References: 1.Hemmati M, Expression and Purification of Recombinant Mycobacterium Tuberculosis Diagnosis Antigens, ESAT-6, CFP-10, and ESAT-6/CFP-10, and Their Potential Use in the Diagnosis and Detection of Tuberculosis, Iranian Red Crescent Medical Journal, Vol. 13, No.8, Pages 558-565,(2011). 2.Danica Helb, Rapid Detection of Mycobacterium tuberculosis and Rifampin Resistance by Use of On- Demand Near Patient Technology , Journal of Clinical Microbiology,Vol. 48, No. 1, Pages. 229237, (2010). Figure 3. Simulated Results of the Proposed Cantilevers Figure 5. Displacement Vs Input force for different types of Cantilever structures Figure 1. Deflection of the Cantilever upon selective binding Figure 2: Proposed Geometry of the Cantilever Structures Figure 3 & 4. Simulation results of the different types of Cantilever