2004 4th IEEE Conference on Nanotechnology
A BIOMEDICAL BONE NANO-TRANSDUCER
Kanika Singh
CBME, Indian Institute of Technology, New Delhi-l10016, India, and
SOET, IGNOU University, New Delhi-1 10068
Address for Correspondence: 7/9 MS Bldg, NPL Colony, New Delhi-110060, India.
Email: kanika-singh-20@yahoo.com
ABSTRACT square, semi-circular and ring types, by using a hexa
Bones are now considered as a well accepted series of blade. Electric contact has been provided with firing on
piezoelectric materials. Several researchers have used the silver using air-dry paste on either side of the bone
bone material to develop piezoelectric sensors for the tablets. After proper silvering, the tablets have been poled
measurement of pressure, force, acceleration and other with dc electric field of 2.5 kV/cm to 10 kV/cm at
such parameters. However, with the advancement of elevated temperature (60-120 degree C, here). The
technology in sensor systems, micro and nano-scale measurements of piezoelectric properties have been made
devices are now being developed by using semiconductor for both poled and unpoled samples [SI.
or biological materials, all over the world. Bio-chips
based on DNA, and Bio-MEMS, etc are some of the 2.2 From Bone Powder
examples. In the present research, new bone chips have
been developed for various sensor applications, mainly Different animal in vitro bones (goat, ox,
micro or nanoscale systems. Design and fabrication buffalo), have been kept in saline solution for two days
aspects of the bone sensor chips for nano-transducers are and then crushed into the powdered form by using an
discussed in detail here. Possible biomedical applications electric bone cutter, as is used by the craftsmen. The
of these chips are also given in brief. powder thus obtained has been subjected to grinding with
the help of dry ball-milling for 24 hours. The bone
KEY WORDS powders have been mixed with a few drops of polyvinyl
Piezo-electricity, bone, sensors, diagnostic probe, acetate (PVA) and compressed into the circular discs with
microphone pick-up, vibration sensor. the diameter of 22.5 mm and thickness 2.5 mm. These
discs have been kept drying for 15 days. These bone
powder discs have been electroded and poled with firing
on silver by vacuum process as well as by using air-dv
1. Introduction paste on either side with the dc electric field of 2.5 kVlcm
to 10 kV/cm at elevated temperature(60-80 degree C).
The piezoelectric property of bone discovered The measurements on the test pieces have been made in
earlier [I-41 has been utilized to develop bone-chip this case also, on poled and unpoled samples [SI.
sensors in the present investigation [5, 61. The study
shows that a relationship exists between the formation and
the deformation of the bone on one hand and the stress-
3. Measurements
generated potential on the other, and the bone has been
considered mechanically deformed and electrically a The measurements of electrical, piezoelectric
homogenous and anisotropic solid. Thus the bone and mechanical parameters at room temperature have
been made, after a lapse of five days of the poling of the
functions as a transducer or sensor, converting mechanical
discs and bone specimens for better stability of various
energy to electrical energy or vice versa. In the present
work, bone sensor elements of variable dimensions have parameters due to aging. While the measurements of
capacitance and dielectric loss factor (tan 3 at 10 kHz has
been prepared from the solid bone as well as from bone
powder. been made by LCR bridge (with sensitivity of 0.1, the
same from 100 kHz-500 kHz has been measured by
impedance bridge. The measurement of resistivity has
2. Design and.Fabrication been carried out by employing an ohm-meter. The
piezoelectric charge constant (dn) has been measured by
2.1. From Solid Compact Bone using Berlin Court’s d33 meter model CPDT3300. The
dielectric constant, voltage constant and other parameters
The in vitro bones, goat bones in this case, have have been calculated by using the conventional
been kept in the saline solution at least for two days. The relationships [5,6]. Table 1 gives the average piezo-
hones have then been cut to small tablets of different
shapes of discs, namely, circular, cylindrical, rectangular,
02004 IEEE
0-7803-8536-5/04/$20.00 438
electric parameters of bone samples used in the present 30 MHz make Wave Tek, San Diego, California, USA.
work. The receiving sensor was coupled with the transmitting
sensor in a water tank, which was connected to a pulse-
receiver, Model 5052 PR, make Panametrics, USA. Both
Table 1: Bone Sample Characteristics transmitted and received pulses were displayed on CRO
(Cathode Ray Oscilloscope) on separate channels, in
Bone Powder order to identify transmitted And received signals. The
transmitting sensor was fed with the tone burst signal and
Density (Kdcubic m) 1980 2770
the output from the receiving sensor was read on the CRO
Capacitance @F) screen. The frequency response of the sensor thus
53.70 14.60 developed is in the frequency range 1 MHz'to 30 MHz,
Loss Factor (tan J having resonance fundamental frequency at 15 MHz and
0.0275 0.040
Dielectric Constant (K' T)
its second harmonics at 25 MHz. The directivity pattern
64.10 23.20 of the sensor was studied by using a hydrophone. The
Resistivity (ohdcm) bone sensor element has been found to have low voltage
17.5XIO' 52.OXIO' and charge constants than that of PZT and quartz type
Charge Constant (d,,XlO~"CIN)
55.0 30.5
transducers but with the low dielectric constant, low
Voltage Constant (g,,xIo'v ") characteristic impedance, broad frequency range and low
95.0 148.0 acoustic impedance. These are easy to make in small sizes
and are useful in the characterization of hard biological
tissues like bone due to high resolution and good acoustic
4. Development of Bone Chip Sensor and matching.
Performance Results
6. Conclusion
4.1. Development
The development of bone-chip based nano-
The sensing elements of diameter, 8 - 35 mm sensors and nano-transducers has been discussed here.
and thickness, I - 3 mm, were made from the wall of
bone matrix as well as from bone powder. An air dry References
colloidal silver paste was applied on both of the opposite
surfaces of the sensing element to make them as positive [I] E. Fukuda and 1. Yasuda, On piezoelectricity in bone.
and negative electrodes. The standard thin, PVC covered .I PhysSoc. Japan, 12,1957,1158.
shielded wires of copper were used for electrical [Z] A.A.Marino and R.O.Becker, Piezoelectric effect and
connections. The crystals were mounted in a cylindrical growth control in bone. Nature, 228,1970, 413-414.
aluminium probe casing. The thin sheets of perspex of [3] E. Fukuda and I. Yasuda, Piezoelectric effect in
thickness 0.5 to 1.5 mm were pasted on the front surfaces collage. Japanese J.Appl Physics, 3, 1964, 111.
of the crystals for their protection. The tungsten powder [4] M.A.Andrew and R.O.Becker, Piezoelectricity in
of density 10.5 gm-cm-3 was used as a hacking material hydrated frozen bone and tendon. Nature, 253, 1975, 627.
by using araldite as a binder to improve the performance [5] V.R.Singh, S.Yadav and A.Ahmed, Electrical and
and band width of the sensor. The BNC connector was mechanical properties of animal in vitro bones. J. Instn
used for the external connections. The sensor was kept for Engrs (India), 68,1988,4347.
two days for the setting and drymg of the material. [6] S . Yadav and V.R.Singh, Development of a
piezoelectric bone microphone pick up for vibration
4.2. Characterization measurements., Innov. Tech. Biolog. Med., 11, 1990, 89-
95.
The bone sensors were characterized and tested [7] V.R.Singh, S.Yadav and A. Ahmed,A piezoelectric
for their frequency response and directivity. The bone bone hydrophone for medical ultrasound applications.
sensor testing was based on the pulse-echo transmission Proc. I f h Ann Int IEEE Conf on Engg in Med and
technique. The transmitting sensor was excited with the Biologv, New Orleans, USA, Nov 4-7, 1988.
help of a frequency generator, model 164, range .OIHz -
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