The 14th IFToMM World Congress, Taipei, Taiwan, October 25-30, 2015
DOI Number: 10.6567/IFToMM.14TH.WC.OS1.019
Method to obtain only targeted substances from an artificial circulatory system
Shunsuke Nagahama∗
Shotaro Iida† Hiroki Yoneyama‡
Waseda University
Tokyo, Japan
Abstract— In this paper, we propose a filter system that
can selectively obtain the required substances from an artificial circulatory system. The blood circulatory system of
the human body keeps us healthy. We consider this system
to be useful for a robot system to maintain its condition.
To realize an artificial circulatory system like a human
body, it is important to deliver various substances with only
a single vessel and extract only the required substances
from them. We propose a method to deliver encapsulated
substances. By using this method, each substance can be
delivered without mixing for easy separation. We developed
a filter system that can trap only the required substances
without clogging based on differences in the capsule size.
We conducted experiments to evaluate the separation performance of the system. We were able to obtain only the
targeted substances with this system. We developed an impurity filtration system as an application of our system.
Keywords: Artificial circulatory system, encapsulation, filtration
system
I. Introduction
In the human body, the blood circulatory system serves
an important role for homeostasis. The system has four
main functions: (1) transferring nutrients, oxygen, waste
products, and so on; (2) sustaining normal bodily functions;
and (3) protecting the living organism from outside factors.
For robots, these functions can be replaced with the following analogous functions: (1) supplying electricity and
fuel for the actuators, sensors, computers, and so on; (2)
regulating the temperature of the components (e.g., motor)
and lubricating joints and removing waste oil and byproducts that negatively affect the performance of the system;
and (3) repairing the damaged components on its own. To
realize the functions of the robot system, we previously developed an artificial circulatory system in earlier research
[1]. The system has three functions: (1) supplying energy
for the fuel cell, (2) cooling the motor, and (3) sealing defects that occur in a tube by clotting the mixed liquid.
In terms of other work related to an artificial circulatory
system, we developed the magnetic powdery wire (MPW)
[2] and magnetic powdery sensor (MPS) [3]. The MPW
is a wire with a self-repairing function. The wire consists
∗s
[email protected]
[email protected]
‡ h [email protected]
§ [email protected]
†s
Shigeki Sugano§
of iron powder and magnetic field. The iron powder lines
up along the magnetic field and becomes a wire that can
transfer electrical signals. When the wire is broken, the
wire is repaired by the transfer of iron powder to the broken area. The MPS is a contact displacement sensor with
a self-repairing function of sensing area. The sensor consists of iron powder and magnetic field. The iron powder
lines up along the magnetic field and becomes a sensing
area whose resistance value changes corresponding to the
displacement. When the sensor is broken, the sensor is repaired by the transfer of iron powder to the broken area.
Various functions have been realized for the artificial circulatory system. However, different materials are needed
to realize these various functions. For example, lubricant is
needed for sliding portions, and repairing agents are needed
to repair worn members. When various substances exist in
the same vessel of a circulatory system, some problems will
appear. One is that the substances will become mixed and
difficult to separate. In addition, the substances may react
with each other. On the other hand, if many vessels are prepared for each substance to avoid the problem of mixing,
the occupying space of the vessels will increase, and the
system will need many pumps.
We propose a method to deliver various substances with
a single vessel. We solved the above problems by using encapsulated substances. Various encapsulated substances are
separated easily and do not need many vessels and pumps.
This method can be used to deliver materials not only in the
solid state but also in the liquid state without mixing. To
separate the various encapsulated substances, we developed
filters to separate them based on differences in the capsule
size.
II. Artificial circulatory system for the robot
Fig. 1 shows our proposed system. First, the robot takes
in substances (e.g., lubricants and repairing agents) from
outside. These substances are processed in the reactor. The
process includes encapsulation, chemical conversion, and
breakdown. The processed substances flow through the vessel and are delivered and supplied to the components of the
robots (e.g., sliding portion). By supplying the substances
to the components, the maintenance of a robot can be performed automatically.
We focused on the filter, which extracts only the required
substance. Human cells obtain only the required nutrients
from blood. Similarly, it is important to supply only the
Fig. 1. Overview of artificial circulatory system
required substances to the components of a robot.
A. Filtering system
We propose a filtering system so that components only
obtain the required substances (Fig. 2). In this system, substances are separated according to size. At the first filter,
substances that are larger than the target capsules cannot
enter the acquisition area because the pore size of the filter is too small than the substances. At the second filter,
capsules that are smaller than the target capsules leave the
acquisition area because the pore size of the filter is larger
than the substances. The fluid flows in a circle at the second
filter. The target capsules move circularly and stay at the
area without clogging the filter. By using this filter, only required substances are taken at the acquisition area (Fig. 3).
Fig. 3. Circulatory system with first and second filters
B. Encapsulation
We developed an alginate capsule that includes an substance(Fig. 4). The capsules are classified into two structures (Fig. 5). Mononclear type is used to transfer the liquid
substance. Multinuclear type is used to transfer the solid
substance. In this paper, we developed multinuclear type
capsule.
Fig. 2. Filtering system: Red area shows an acquisition area that stores
medium-sized capsule (acquisition target). Large capsules (substances)
cannot enter the acquisition area. Small capsules (substances) can enter
the acquisition area but exit the area through the second filter.
Fig. 4. Overview of encapsulation
One hundred balls was added into the vessel of the circulatory system, and a pump was driven. We counted the
number of balls that passed through the acquisition line.
The flow ratio was varied (0.2, 0.4, 0.6,0.8), and the capsule
acquisition ratio under each condition was observed. The
capsule acquisition ratio is the number of balls that passed
through the acquisition line against the number of all balls
added into the vessel. The pore size of the filter was 5.5
mm. The average ball size was 4.7 mm.
Fig. 5. Types of capsule
III. Experiments
We conducted two experiments. In the separation experiment, we confirmed that the filter was able to separate
various capsule sizes properly and that only target capsules
were obtained at the acquisition area. In the amount adjustment experiment, we confirmed that the amounts of capsules acquired at the acquisition area can be adjusted.
IV. Results
A. Separation experiment
As shown in Fig. 6, the number of targeted balls in the
acquisition area increased over time. On the other hand, the
large balls did not go into the acquisition area. The small
balls moved out of the area after going into the area.
A. Separation experiment
In this experiment, we evaluated the separation performance of the filter. We also confirmed that the system can
prevent clogging of the filter.
Three sizes of polyethylene balls were prepared. Each
size had 10 balls. Table I gives the sizes. They were added
into the vessel of the circulatory system, which is shown in
Fig. 3. Table II presents the pore sizes of the first and second filters. We drove a pump (PSK-540X, KOSHIN) and
confirmed that the system could obtain only the targeted
substances (i.e., the medium-sized ball) in this experiment.
The flow rate of the pump was 7 L/min. The inner diameter
of the vessel was 15 mm. We counted the change in the
number of balls obtained at the acquisition area for 5 min.
TABLE I. Size of polyethylene ball
Ball diameter [mm]
Small ball
Middle ball
Large ball
3.175
4.763
6.35
Fig. 6. Change in number of trapped balls in relation to time
B. Amount adjustment experiment
As shown in Fig. 7, the number of balls that passed the
acquisition line increased with the flow at the acquisition
line.
TABLE II. Filter pore size
Filter pore size [mm]
1st-filter
2nd-filter
6
4.5
B. Amount adjustment experiment
It is necessary to supply only the needed amount to robot
components. In this experiment, we adjusted the numbers
of balls that passed through the acquisition line by changing
the flow ratio (Fig. 2). The flow ratio is the flow at the
acquisition line against the full flow. The ratio was adjusted
by changing the heights of the acquisition and transfer line.
Fig. 7. Change in number of balls that passed acquisition line in relation
to flow ratio
V. Discussion
A. Separation experiment
The targeted balls were trapped. However, a few of the
small balls remained in the acquisition area. It was difficult
to remove all of the small balls from the acquisition area,
but we were able to solve the problem by increasing the
flow rate at the acquisition area and the number of pores
of the second filter. For the filter design, it is important to
consider the tradeoff with clogging. If the flow rate and
number of balls are too great, the target balls will be drawn
toward the second filter, and the filter will be clogged.
Fig. 8. Alginate capsule including activated carbon
B. Amount adjustment experiment
It was possible to adjust the number of balls trapped in
the acquisition area by adjusting the flow ratio. However,
in this experiment, we adjusted the height of the lines to adjust the flow ratio. Another method would be better. Using
valves is a simple method, but they will become clogged
with various things such as balls or capsules. We consider
changing the inner diameter of the vessels to be better. By
using this method, it will be possible to adjust the flow ratio
without clogging.
Fig. 9. Circulatory system: system containing impurities (left) and
overview of system (Right)
VI. Application
A. Impurity filtration system
We made an alginate capsule that included activated carbon as an adsorbent (Fig. 8). Activated carbon can mainly
adsorb to non-polar substances. By encapsulating an adsorbent into the alginate capsules, we could obtain capsules
that adsorb to various substances.
First, sodium alginate (0.56 g) was added into pure water (51 g), and the liquid was stirred until the substance
dissolved in the water. Next, activated carbon (2.0 g,
TAIKO S-type, FUTAMURA) was added. The solution
was dropped into a 2 wt% CaCl2 solution, and they were
dipped for 30 min. After they were picked out, they were
dipped into a 10 wt% CaCl2 solution. Thus, encapsulated
activated carbon was obtained.
The process of removing impurities was divided into two
parts: (1) adsorbing impurities into the capsule and (2) separating the capsule from the flow of the circulatory system.
After the capsule adsorbs the impurities, we can easily exchange capsules. We conducted adsorption experiments.
Only the second filter was used in this experiment. The
circulatory system was filled with water (about 1200 ml),
and a food coloring agent (0.16 g) was added as an impurity (Fig. 9). The above encapsulated activated carbon
(11.7 g) was added into the system from the input port, and
a pump was driven. The solution was sampled every 24 h,
and the ultraviolet visible absorption spectrum of the solution was measured (V-630, JASCO). The capsules were
trapped without clogging (Fig. 10) As shown in Fig. 11, we
confirmed that the proposed system can remove impurities
from a liquid.
Fig. 10. Trapped capsules at second filter; the capsules were trapped
without clogging
Fig. 11. Change in impurity concentration over time
VII. Conclusion & Future works
We propose an artificial circulatory system that can supply various substances to robot components as capsules. In
addition, we propose an impurity filtration system as an
application to remove impurities with encapsulated adsorbents.
In future work, we will apply our system to other uses
(e.g., lubrication of robot joints).
References
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