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Jakob Schloer
Sperm-Driven Magnetic Microrobots
Cairo, Egypt
Final Report
Development and Control of Sperm-Driven Magnetic
Microrobots
German University in Cairo (GUC)
Egypt; July 30, 2015
At the beginning of my nal report I would like to say that I had an amazing time in Egypt. I gained a
lot of life and work experiences, made a lot of friends and got a deep insight into the Egyptian society
and culture. These would not have been possible without the great support of Dr. Anke Klingner, Dr.
Islam Shoukry and specially my friend Mohamed Kateb, to all of whom I would like to express my
gratitude. I would do this internship any time again.
First I will write about my work and later about my life in Cairo.
I worked in the Medical Micro and Nano Robotics Laboratory1 at the German University in Cairo
(GUC). My project belonged to the physics and mechatronics department of the university. The title
of the project was "Development and Control of Sperm-Driven Magnetic Microrobots". We produced
half biological robots and steered them in a magnetic eld. The half biological robot consists of a
magnetic particle which is attached to a sperm cell. The sperm cell provides the propulsion of the
microrobot whereas the magnetic particle is needed for steering the microrobot in the magnetic eld.
A possible future medical application for the microrobot could be the targeted transportation of drugs
inside the human body.
The agellated swim of the sperm cell has been detected as a very ecient way of propulsion. This
biological-inspired movement has been utilized to design and develop microrobots. A microrobot with
the morphology of a sperm cell has been fabricated in a related project in the MNR-laboratory.2
In the related work SU-8 polymer was used for
the tail and a cobalt-nickel layer on the head to
furnish a dipole moment. The dipole moment
is needed to provide the propulsion of the microrobot by using an external rotating magnetic
eld. Besides the good results of the project the
propulsion eciency of biological cells are much
better than the eciency of the sperm-shaped
microrobot. Especially, using biological cells the
complicated magnetic setup for applying the rotating eld is not needed. For this reasons researchers tried to build a half-biological microrobot. One of the rst idea was to produce a
Figure 1: A sperm-shaped microrobot which is prosmall tube which is closed on one side. The bacduced using electrospinning and a picture
teria swim inside and move the tube. The halfof the electromagnetic setup 2
biological microrobot can be steered by a simple
magnetic setup. Nevertheless the motility of the
1
2
http://mmnrobotics.com/
Islam S. M. Khalil, Ahmet Fatih Tabak, Ahmed G. El-Gazzar, Louay E. El-Khouly, Anke Klingner, Metin Sitti:
Sperm-Shaped Magnetic Microrobots: Fabrication using Electrospinning, Modelling and Characterization; March 4,
2015
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Jakob Schloer
Sperm-Driven Magnetic Microrobots
Cairo, Egypt
half-biological microrobot is low because of the weight of the tube.3 Based on these previous work our
aim is to produce smaller and faster half-biological microrobots. The propulsion of our microrobot is
provided by a sperm cell. We chose sperm cells because of their high eciency to swim against a ow
and because of its easy way to get them. The control of our microrobot is achieved by small magnetic
particles which are coated with polystyrene. The polystyrene surface allows the sperm to attach to
the iron particle. The microrobot is steered with a magnetic setup. It consists of four orthogonal
coils which apply an magnetic torque at the ironparticle to change the swimming direction of the
microrobot.
The four coils are connected to a Printed Circuit Board (PCB) which consists mainly of four
drivers for each coil and an Arduino Mega. The
PCB controls the current of the coils. Our computer program is mainly a closed-loop control.
The camera of the microscope is used to detect
the x-y-position of the microrobot. We set a nal
point at the screen where our microrobot should
go. The program calculates the direction between
microrobot and end point and applies a specic
current at the coils to get a magnetic gradient
and a torque at the iron particle. Then the microrobot changes its swimming direction. The cam- Figure 2: Setup for our magnetic eld at the microera detects the new position of the microrobot
scope
and calculates a new swimming direction. If the
new direction is not equal to the old direction, it
will change the swimming direction of the microrobot again until it reaches the nal point. After reaching the nal point the microrobot swims circles around this point. The development of the program is
the work of another project. For this reason I don't explain this program in detail.
The main issue of our research is the coating of the iron particles to achieve adhesion with the sperm
cells. We coated the ironparticles with dierent types of polystyrene. Therefore we used the process
of electrospinning.
Our setup for electrospinning consists of a pump,
an electrode, a grid collector and an high-voltage
DC generator. The high-voltage generator is connected to the collector and to the tip of a syringe
(the electrode). The syringe is xed to the pump
which controls the ow rate. The ironparticles
and a polystyrene solution are added to the syringe. We set the ow rate and the voltage of the
high-voltage generator. The voltage between the
electrode and the collector can be increased from
10kV to 20kV. At a specic threshold voltage a
droplet of the uid is drawn out of the pipe into
a cone-shaped terminus. It sprays downwards as
Figure 3: Setup for electrospinning
a jet towards the collector as a hardly visible
nanoscale bre. The solvent of the polystyrene
3
Islam S.M. Khalil, Veronika Magdaz, Samuel Sanchz, Oliver G. Schmidt, Sarthak Misra: Biocompatible, accurate, and
fully autonomous: a sperm-driven micro-bio-robot; 6 March 2014, Berlin Heidelberg, Springer
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Jakob Schloer
Sperm-Driven Magnetic Microrobots
Cairo, Egypt
solution evaporates at that time. The result is a dry polystyrene nanoscale bre on the collector. Beside of electrospinning there is electrospraying. It is the same process with a dierent voltage, ow rate
and viscosity to produce polystyrene droplets instead of bres. Using the process of electrospraying
we produce polystyrene coated ironparticles.
We tried dierent polystyrene solutions and dierent treatments of the polystyrene surface because
sperm cells adhere to hydroxyle groups on the surface. At the beginning we produced a 10% polystyrene
in Dimethylformamide (DMF) solution and treated the surface in three dierent ways:
ˆ we added a few drops of 98% sulfuric acid at 37◦ C to the solution and desolved it by steering it
for 3 hours
ˆ we treated the dry beads with UV-light for 30 min (≈ 5 mW
)
cm2
ˆ we treated the surface of the beads with 10M hydrochloric acid for 30 min
None of these methods achieved a quantitative result. We observed adhesion randomly around one
out of ve times. Pictures of one of the best results at May 10, 2015 are shown below in gure 4. We
treated the beads with sulfuric acid and we found three sperm cells which adhere to the beads in 15
min.
(a)
(b)
(c)
Figure 4: Adhesion of Spermcells with sulfuric acid treated polystyrene beads (May 10, 2015) 20x
magnication
Because of the problems to reproduce our results with one of these methods we started working with
Achmed Said, a chemistry PHD from the Cairo University. He suggested to use the same polymer
structure like the polymer structure of the surface of the human egg cell. Therefore we desolved 10%
Polyvinyl chloride (PVC) in Tetrahydrofuran (THF) and added about 2% starch to the solution while
steering and heating. The last eort during my internship was the production of the beads with
electrospinning. The PVC beads were looking the same as the polystyrene beads. Unfortunately I had
to leave Egypt before we were able to do the experiment with the sperm cells.
In conclusion the work in Egypt was really interesting especially to work in a team with engineers and
chemists. I learned a lot about polymer chemistry and arduino programming.
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Jakob Schloer
Sperm-Driven Magnetic Microrobots
Cairo, Egypt
The second part of my report is about my life in Cairo. My internship was about three months from
the 1st of May to the 22nd of July. When I got accepted for the "RISE weltweit" scholarship in Egypt
I contacted my supervisor Dr. Anke Klingner. With her help I found an accommodation and I booked
a ight. It was really easy to get the Egyptian visa. I could have applied for one at the Egyptian
embassy in Germany but I had too less time. So I just got the tourist visa for one month at the airport
in Cairo and extended it later in Cairo. To get the extension I had to go to the government oce at
Tahrir square. Although I went there with an Egyptian friend we had to go there three times in a row,
every time standing and waiting to get the extension. So I would recommend to apply for the visa in
Germany or to get the tourist visa and pay a small ne at the departure (it doesn't matter how long
you stay there the ne is always just 20¿).
After arriving at Cairo airport my supervisor picked me up and we went to the dormitory of the
German University where I stayed. The dormitory is in the compound Rehab in the district of New
Cairo. I had my own room in a at shared with 6 students. In the dormitory lived about 150 students.
Living there was like living in a hotel. I took my key from the security guard when I entered and gave
it back when I left. Furthermore, kitchen, bathroom and my room were cleaned every two days and
my laundry was done whenever I gave it to the cleaning service. So everything was clean even it was a
dormitory for just male students. Besides this I really enjoyed living in the dormitory because I stayed
there only with Egyptians. This gave me the opportunity to get in contact with them and their way of
life. In my experience it is very easy to make friends in Egypt because all Egyptians are very friendly
and hospitable. I was invited for dinner many times and all the people I met oered their help. So
they made my rst time in Egypt not hard or lonely at all.
Immediately the next day I went to university by the university bus which stopped directly in front
of the dormitory. Compared to the public transport in Egypt the buses of the German University are
very comfortable. There are buses for each district in Cairo going to university and returning every
two hours. The German University is placed in the same district like the dormitory so it just took
about 20 minutes to go there. That's a very short distance in a town with 20 to 25 million people. At
the university most of the students have breakfast with typical Egyptian food and coee which you
can buy at the platform. The platform is an area in front of the buildings with dierent stores and
places to sit where students meet during their breaks. The rst day I bought a phone card over there
which is very cheap in Egypt.
At rst I was afraid how to communicate with people but all students at the university are speaking
English. It is remarkable that only good educated people are speaking English in Egypt. In the streets
I rarely found people who were able to speak English. So I had to speak a bit Arabic. I was glad
that I took two Arabic courses at my university in Germany before I went to Egypt. So even the
Egyptian dialect is dierent from the standard Arabic I was able to learn words quickly. My friends
helped me a lot learning their language. So at the end I was able to communicate a bit in Arabic. I
would recommend to attend a language course in Egypt, too. I didn't do that but I think I would have
learned the language faster and properly. There were also a lot of private teachers who were not very
expensive.
I chose to go to Egypt because I wanted to get to know a life and culture dierent from the western
one. The Egyptian society has a big gap between rich and poor people. Most of the people don't have
much money and are less educated. The minority has enough money to aord to go to university. On
one hand there are places in Cairo which are clean and looking like Europe. On the other hand there
are places like the garbage city where people live in rubbish made huts. Nevertheless Egyptians have
in common that they are very friendly and religious. About 90% of the population are Muslims. So
most of the women in the streets are wearing a Hijab or a Burka but at the university just half of
the women are wearing a hijab. I mentioned that the mindset of people diers depending on their
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Jakob Schloer
Sperm-Driven Magnetic Microrobots
Cairo, Egypt
education and on their incomes. For instance, I made the experience that in rich families the girls
can decide by their own if they want to wear a hijab or not. In poor families they seemed to have no
choice. In general the family in the Egyptian society has a very high value. That's why most of the
people live with their parents till they get married.
Also the daily life diers a lot from Germany. Specially in Summer the people are in the streets after
sunset because during the day it's too hot. All supermarkets, hairdressers, etc. are open till 12 o'clock
at night or longer. So I met my friends somewhere in the streets nearly every night to eat together.
Egyptian food is very tasty because it's cooked with a lot spices. There exist a lot of typical Egyptian
food which is sold on the street and which is very cheap, too. Like in the most Islamic cultures it is not
common to drink alcohol. In Egypt it is legal to drink alcohol in bars or at home but it is forbidden
to drink it in public. Still it's not a common thing to do.
In the time I was in Egypt a lot of my German friends asked me about the safety there. In my opinion
Egypt is a safe place to stay. Of course there are some places you should not go alone at night or some
areas near the border to Israel where you are not even allowed to go but I never felt unsafe somewhere.
Also it's no problem to travel in Egypt. Specially the Red Sea is a beautiful place to go. Depending
where you want to go you can go by bus, train or plane. Mostly I had to ask my friends how to get
there because till now you can't nd any travel-information on the internet. For short distances I
normally used taxis which are very cheap there.
My time in Egypt was amazing. I learned a lot at work, lived nearly an Egyptian life for three months
and found a lot of friends there. It was denitely not the last time I visit Egypt. All these would
not have been possible without the organization of "DAAD Rise weltweit". Thank you so much. If I
gained your interest about going to Egypt, please feel free to contact me. I would be glad to answer
your questions and to help you.
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