An optoelectronic apparatus has been invented as a noninvasive means of measuring the concentration of glucose in the human body. The apparatus performs polarimetric and interferometric measurements of the human eye to acquire data from which the concentration of glucose in the aqueous humor can be computed. Because of the importance of the concentration of glucose in human health, there could be a large potential market for instruments based on this apparatus

Ansari, Rafat R.

Rovati, Luigi L.

NASA Technical Reports Server

with N – 1 semiconductor layers; an electri-
cally and thermally conductive plate, denot-
ed the cold plate, on the side to which heat
is to be transferred; and small batteries or
other DC electric power sources and wiring
connected to the hot and cold plates and to
the semiconductor layers. Under the influ-
ence of the electric potential field applied by
the DC sources, some of the thermally agi-
tated electrons would be adiabatically swept
away from the hot plate into the first layer of
nanotubes. (Because of this mode of oper-
ation, the device could also be called a
thermionic cooler or heater.) The applied
electric field would accelerate the electrons
moving in the nanotubes, giving them
enough kinetic energy to overcome the
Schottky barrier at the nanotube/semicon-
ductor interface. Consequently, the Schottky
barrier would act as a one-way valve for
energetic electrons.
In the same manner as described above,
thermally agitated electrons in each semi-
conductor layer would be made to travel
through the next nanotube layer to the next
semiconductor layer, and so forth until the
electrons reach the cold plate, from whence
they would be removed via an ohmic con-
tact into the wiring. The closed electric circuit
would maintain charge neutrality, supplying
electrons to the hot plate and semiconduc-
tor layers to replace those removed by
thermionic emission and applied electric
fields. In addition to a DC potential applied
between the hot and cold plates, DC bias
potentials could be applied to the semicon-
ductor layers to control the quantum-
mechanical tunneling of electrons through
the Schottky barriers.
It will be necessary to perfect a number of
techniques in order to fabricate TEB
devices. Among these are techniques for (1)
depositing RTSPs or growing highly pure,
aligned single-wall carbon nanotubes on
electrically and thermally conductive sub-
strates that can serve as hot and cold
plates; (2) cutting the nanotubes to make
clean, flat planes on which semiconductor
layers can be deposited; and (3) depositing
RTSPs or growing highly pure, aligned sin-
gle-wall carbon nanotubes on the semicon-
ductor layers. The overall thickness of a TEB
device would be determined largely by the
number of carbon-nanotube layers, the
length (≈5 µm) of the nanotubes in each
layer, and the thicknesses of the semicon-
ductor layers. It should be possible to make
TEB devices so thin that they could be
incorporated into or onto flexible structures.
This work was done by Sang H. Choi of
Langley Research Center. Further infor-
mation is contained in a TSP [see page 1].
LAR-16222
NASA Tech Briefs, March 200320
An optoelectronic apparatus has been
invented as a noninvasive means of mea-
suring the concentration of glucose in the
human body. The apparatus performs
polarimetric and interferometric measure-
ments of the human eye to acquire data
from which the concentration of glucose in
the aqueous humor can be computed.
Because of the importance of the concen-
tration of glucose in human health, there
could be a large potential market for instru-
ments based on this apparatus.
The apparatus (see figure) includes a light
source equipped with a linear polarizer and
a quarter-wave retarder to generate a beam
of circularly polarized light. The beam is
aimed at an eye at an angle of incidence (θi)
chosen so that after refraction at the surface
of the cornea, it travels through the aqueous
humor and impinges on the crystallin lens at
the Brewster angle [θb = arctan(nl/nh), where
nl and nh are the indices of refraction of the
lens and the aqueous humor, respectively].
The portion of the beam that enters and
passes through the eye is denoted the
probe beam. The portion of the beam
reflected from the cornea is further reflected
by a mirror and used as a reference beam
for low-coherence interferometry.
The Brewster-angle arrangement causes
the portion of the probe beam reflected from
the lens to be linearly polarized perpendicu-
lar to the plane of incidence (which here
coincides with the plane of the page). As the
reflected probe beam traverses the aqueous
humor, glucose molecules rotate its plane of
polarization. This rotational effect is well
established: It is characterized by previously
determined, wavelength-dependent propor-
tionality between (1) the angle of rotation of
the plane of polarization and (2) the product
of the concentration of glucose and the
length of the optical path through the solu-
tion (in this case, aqueous humor) that con-
tains the glucose. Hence, if one can
measure the rotation of polarization of the
reflected light and the length of its path
through the aqueous humor, one can calcu-
late the concentration of glucose by use of
the aforementioned proportionality.
After leaving the eye, the reflected probe
beam enters beam splitter 1. Part of the
probe beam passes through beam splitter 1
and goes to a polarimetric sensor, which
Optoelectronic Apparatus Measures Glucose Noninvasively
The concentration of glucose is obtained through a
combination of interferometry and polarimetry.
John H. Glenn Research Center,
Cleveland, Ohio
0A TEB Device would exploit thermionic emission, ballistic transport of electrons in carbon
nanotubes, and Schottky barriers at nanotube/semiconductor interfaces. The thickness of
each nanotube layer would be of the order of 5 µm.
Bundled, Aligned Carbon Nanotubes
Semiconductor Layers
Cold
Plate
Hot
Plate
e— e—
Heat
In
Heat
Out
1st Layer 2nd Layer 3rd Layer N th Layer
e—
https://ntrs.nasa.gov/search.jsp?R=20110023713 2019-08-30T18:22:33+00:00Z
measures its angle of polarization. From this
angle and the known orientation of the plane
of incidence on the lens, the rotation angle
can be determined. Part of the probe beam
leaving the eye is reflected from beam split-
ter 1 toward beam splitter 2, wherein it is
combined with the reference beam. The
combination of the probe reference beams
impinges on a photodetector for use in low-
coherence interferometry to measure the
total length of the path of the probe beam
through the aqueous humor. By virtue of
symmetry, half of this path length contributes
to the measured rotation and is, therefore,
the length to use in calculating the concen-
tration of glucose.
As described thus far, the principle of
operation does not necessarily involve the
use of multiple wavelengths. The value of
multiwavelength operation lies in the possi-
bility of compensating for rotation caused by
analytes other than glucose. By measuring
at a number of wavelengths equal to the
number of analytes (including glucose) that
contribute to rotation and knowing the
wavelength-dependent specific rotation,
one can solve the system of linear equations
for the rotation at the various wavelengths to
extract the concentration of glucose (and,
incidentally, of the other analytes).
This work was done by Rafat R. Ansari
of Glenn Research Center and Luigi L.
Rovati of the University of Brescia.
Further information is contained in a TSP
[see page 1].
Inquiries concerning rights for the com-
mercial use of this invention should be
addressed to NASA Glenn Research
Center, Commercial Technology Office,
Attn: Steve Fedor, Mail Stop 4–8, 21000
Brookpark Road, Cleveland, Ohio 44135.
Refer to LEW-17216.
NASA Tech Briefs, March 2003 21
Light Beams Are Reflected and Transmitted by several components of the eye. The polarimetric and interferometric properties of the reflected and
transmitted beams contain information on the concentration of glucose in the aqueous humor.
Aqueous Humor (nh)
d1
Reference Beam
Air Cornea
Beam Splitter 1
Beam Splitter 2
Photodetector for
Low-Coherence Interferometry
Control and
Data-Analysis Unit
θb θb
Lens (nl)
θt
Quarter-Wave Retarder
Linear Polarizer
Circularly Polarized Beam
Multiple-Wavelength
Light Source
Polarimetric
Sensor
Mirror
θi
θt
A floating apparatus denoted a tempera-
ture probe aquatic suspension system
(TPASS) has been developed for measuring
the temperature of an ocean, lake, or other
natural body of water at predetermined
depths. These types of measurements are
used in computer models to relate remotely
sensed water-surface temperature to bulk-
water temperature. Prior instruments built for
the same purpose were found to give inac-
curate readings because the apparatuses
themselves significantly affected the temper-
atures of the water in their vicinities. The
design of the TPASS is intended to satisfy a
requirement to minimize the perturbation of
the temperatures to be measured.
The TPASS (see figure) includes a
square-cross-section aluminum rod 28 in.
(≈71 cm) long with floats attached at both
ends. Each float includes five polystyrene
foam disks about 3/4 in. (≈1.9 cm) thick and
Floating Probe Assembly for Measuring Temperature of Water
Temperatures are measured at
several depths.
Stennis Space Center,
Mississippi


Optoelectronic Apparatus Measures Glucose Noninvasively

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