I. molecular signatures of an unknown sample using

I. Introduction:
This write-up describes the realisation of devices and techniques based on
evanescent field sensing using fibre optic waveguides for mid-infrared (MID-IR)
absorption spectroscopy. Mid-infrared absorption spectroscopy
is the most recent technique for detecting the molecular signatures of an
unknown sample using their fingerprint absorption spectroscopy. In this evanescent
wave field based spectroscopic technique, the optical waveguide can detect any
analytes at very low concentration by using their fingerprint absorption. It
also provides very high sensitivity and selectivity over a wide range of
compounds. The fundamental vibrations of bio-chemical molecules occur in the MID-IR
region. In this region, the magnitude of absorption of bio-chemical molecules is
stronger than their overtone bands in the near-infrared region. In this way it
has been concluded that it is suitable for highly sensitive and specific
absorption spectroscopy.

This research work will explore novel
Mid-IR waveguide based integrated photonic devices.
It will also help to realise the photonic lab on-chip
platform for biomedical diagnostic applications. This work will also involve
the fabrication and characterisation of waveguides and waveguide based devices
such as ring resonators and Mach-Zehnder interferometer. In this work the electromagnetic
modelling of these devices for optimising the performance and for designing
photomask for micro-fabrication.

 

II. Motivation:
There are many types of biomedical sensors available in the world. The sensors
which are getting used as diagnostic tools are such as the glucose sensor, home
pregnancy test, water quality control sensor and calorie management sensor. But
most of these sensors are often bulky, expensive, time consuming and needs an
expert operator. Hence those techniques are out of reach to many number people who
are living in remote areas. This is creating a lot of problem for the
critically sick peoples who need immediate medical help. Presently, in the
modern technique for the flow of disease diagnosis includes the collection of
biological samples such as blood, urine, tissue swabs etc. from the point of view
of care. After that those samples are transported to the centralised
laboratories for examining and testing by the experts. After the reports become
available, the laboratory notifies the clinicians or patients. Accordingly, doctor
improves the treatment of the patient. This evidence based treatment takes a
lot of time mainly for the critically ill patient.

It
is indispensable that maximum number of people should have prior early warning for
medical diagnostics. Hence there is obligation for mass-producible and handheld
prolific medical biosensors which can provide accurate and reliable information
immediately at affordable cost. A medical biosensor is characterised by many number
of features such as its selectivity, sensitivity, responsivity, precision in
values, signal stability, noise, regeneration time, lifetime, affordability,
compactness and portability. There are array of direct and indirect laboratory
based tests available throughout the world, which depends on the medically advantageous
biochemical analytes. A technique or a combination of techniques can be elected
or engineered that offers the customized characteristics of a medical biosensors,
which are based on a specific medical application area. Throughout the world
there are many numbers of widely used medical diagnostics facilities such as
microscopy, chromatography, immunoassays, nucleic acid amplification,
piezoelectric sensors, electrochemical and optical. All of these have their
well-recognised advantages, disadvantages and future scope. The sensitivity and
calibration lags in microscopy in medical schemes. Chromatography techniques
are also highly responsive but it requires extremely expensive medical setup. For
multiplex detection the conventional immunoassays are merely sensile but are
challenging and labour demanding. A tangled sample preparation is demanded in
the nucleic acid amplification but it provides very high molecular meticulosity.
Temperature, Voltage and Stress limits the piezoelectric sensors. The fast
response time and sensitivity pertains in the electrochemical sensors,
resulting in their high success but for increment in selectivity they often
demands the highly stable reference electrode, accurate enzyme based
transducers, isolation and purification of bio molecules from constituents or
contaminants. These fore said techniques consume not only lot of time but also
it is very expensive and may somewhere results in mislaying of bio-chemical activities
in this scenario. Optical biomedical sensors are the recent topic among the researchers
or scientists because of its versatility. An optical biomedical sensor
provides, low-cost analysis, good sensitivity, high response time, good
portability, easy to handle, very compact in size, and remotely controllable in
nature. Optical fibre detection tools have the versatility for integration of
highly multidisciplinary approaches such as microelectronics, biology,
biotechnology and chemistry. Recent health challenges have led to depth of
research and scientific findings of ways to innovate more accurate biomedical
sensors and to improve the performances of biomedical sensing capabilities. Those
devices are life-saving devices that can simply acquire and process the
physiological information. They have the special ability to select one
parameter without interfering any other parameters. There are many types of
biomedical sensors such as direct/indirect, contact/remote, invasive/non-invasive,
real-time/static, and sense/actuate. Each biomedical sensor consists of a
sensing element with a physical transducer that converts a measurand into an
output signal. Basic biomedical instrumentation system has been shown in Fig.1.

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