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 e�cient 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

Figure 1: A sperm-shaped microrobot which is pro-

duced using electrospinning and a picture

of the electromagnetic setup 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 mi-

crorobot by using an external rotating magnetic

�eld. Besides the good results of the project the

propulsion e�ciency of biological cells are much

better than the e�ciency of the sperm-shaped

microrobot. Especially, using biological cells the

complicated magnetic setup for applying the ro-

tating �eld is not needed. For this reasons re-

searchers tried to build a half-biological micro-

robot. One of the �rst idea was to produce a

small tube which is closed on one side. The bac-

teria swim inside and move the tube. The half-

biological microrobot can be steered by a simple

magnetic setup. Nevertheless the motility of the

1http://mmnrobotics.com/2Islam 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 e�ciency 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.

Figure 2: Setup for our magnetic �eld at the micro-

scope

The four coils are connected to a Printed Cir-

cuit Board (PCB) which consists mainly of four

drivers for each coil and an Arduino Mega. The

PCB controls the current of the coils. Our com-

puter 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 speci�c

current at the coils to get a magnetic gradient

and a torque at the iron particle. Then the micro-

robot changes its swimming direction. The cam-

era detects the new position of the microrobot

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 reach-

ing 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 di�erent types of polystyrene. Therefore we used the process

of electrospinning.

Figure 3: Setup for 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 con-

nected 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 sy-

ringe. 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 speci�c threshold voltage a

droplet of the �uid is drawn out of the pipe into

a cone-shaped terminus. It sprays downwards as

a jet towards the collector as a hardly visible

nanoscale �bre. The solvent of the polystyrene

3Islam S.M. Khalil, Veronika Magdaz, Samuel Sanchz, Oliver G. Schmidt, Sarthak Misra: Biocompatible, accurate, andfully 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. Be-

side of electrospinning there is electrospraying. It is the same process with a di�erent voltage, �ow rate

and viscosity to produce polystyrene droplets instead of �bres. Using the process of electrospraying

we produce polystyrene coated ironparticles.

We tried di�erent polystyrene solutions and di�erent 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 di�erent ways:

� we added a few drops of 98% sulfuric acid at 37◦C to the solution and desolved it by steering it

for 3 hours

� we treated the dry beads with UV-light for 30 min (≈ 5mWcm2 )

� 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

magni�cation

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 e�ort 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 o�ce 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 o�ered 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 co�ee which you

can buy at the platform. The platform is an area in front of the buildings with di�erent 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 di�erent 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 di�erent 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 a�ord 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 di�ers 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 di�ers 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 de�nitely 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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