[robotics-worldwide] [jobs] PhD position - FEMTO-ST Institute

aude.bolopion aude.bolopion at femto-st.fr
Wed Apr 29 03:11:38 PDT 2015

   PhD position in microrobotics

Location: AS2M dep, FEMTO-ST Institute, France

Full description:

Handling objects smaller than 100µm remains a challenge that is of 
utmost importance for several application fields, from electronics to 
biology. Microrobotics has developed contact based techniques using 
tools usually inspired from their macrometer size counterparts, such as 
grippers. However these tools are most of the time dedicated to objects 
larger than 100µm. When smaller objects are considered non contact 
actuation is commonly used. It is based on force fields produced by 
remote sources. Several actuation principles have been investigated, 
among which magnetophoresis, acoustic waves, optical tweezers and 
dielectrophoresis. These techniques differ by the nature of the objects 
that can be handled (for example magnetophoresis can only be applied to 
magnetic objects), the level of force that can be applied on the objects 
and the technical constraints induced by the actuators (compactness of 
the final prototype). To ensure long range displacements, in particular 
for conveying of the parts before characterization or assembly, fluidic 
flows inside microchips are often used.


The goal of this thesis is to perform active control based on 
dielectrophoretic actuation. Compared to state of the art systems this 
work will implement closed loop control of the trajectory of the objects 
inside the chips. Enabling precise positioning control is a necessary 
prerequisite to perform complex operations inside the chip in the 
future, such as the mechanical characterization of the objects 
(stiffness measurements for example) before sorting or the assembly of 
different parts (Figure 1).

Two key scientific and technological problematics will be addressed in 
this project: (i) the trajectory and positioning control of the objects 
and (ii) the integration of all the functions in a unique integrated 
device. To be competitive compared to the current systems, two major 
challenges should be addressed: (i) the system should not necessitate 
any complex preliminary step to be used by (it should be plug and play) 
and (ii) thousands of objects must be handled each second. It 
necessitates high speed trajectory control.

First proofs of concept have been demonstrated in the AS2M department of 
FEMTO-ST Institute with high speed closed loop trajectory control of 
artificial beads using dielectrophoresis actuation in a petri dish 
(Figure 2). Dielectrophoresis consists in applying a non-uniform 
electric field to dielectric objects. These objects will experience a 
force either attractive or repulsive depending on the frequency of the 
electric field and of characteristic constants of the objects and the 
medium. Electrodes are commonly deposited on a glass wafer to produce 
the electric field. This technique can be used in combination with 
microfluidic channels. This first step has shown the relevance of the 
approach but several major changes must be made to adapt it to the 
current system. The dielectrophoretic trajectory control should now be 
included into microfluidic channels. In addition trajectory control is 
usually based on visual feedback. However it requires a delicate 
alignment between the camera and the chip, as well as adequate 
lightening conditions. To avoid these cumbersome steps this thesis 
proposes to use impedance spectrometry measurements to perform 
trajectory control. Impedance spectrometry consists in measuring the 
variation of impedance due to the presence of an object between the 

Description of the work

This thesis will rely on the expertise of AS2M department in FEMTO-ST 
where the PhD student will be located and the Prof. P. Renaud team in 
EPFL (Switzerland) for the impedance spectrometry measurements. They 
have recently shown proofs of concept of morphological measurements of 
cells using this technique. Similarly the impedance spectrometry 
measurements also vary according to the position of the cell with 
respect to the electrodes, and thus can be used as a position sensor. 
Tight collaborations with EPFL (that is located 2 hours away from 
Besancon) are forecasted.

Several scientific challenges will be tackled:
-    the modelling of the chip including both the fluidic aspects and 
the dielectrophoretic ones used to move the objects. This model will be 
used for: (i) the definition of design rules for the chips (including 
the fluidic channels and the electrodes) and (ii) getting a model of the 
system that will be inverted in real time to compute the input of the 
system for closed loop control,
-    the determination of control laws dedicated to the non linearities 
of the dielectrophoretic field and to the low inertia of the objects 
inducing large accelerations,
-    the study of detection and tracking algorithms dedicated to 
innovative position sensors (impedance spectroscopy measurements) which 
guarantee the compactness of the chip. In particular the model giving 
the position based on the impedance measurements will be studied ,
-    the realization of an experimental prototype (made in clean room 

All the methodologies proposed during this thesis will be validated 
experimentally. A prototype will be fabricated by the PhD student 
(assisted by the staff of the clean room of FEMTO-ST) and tests will be 
performed on artificial beads. As a first proof of concept the final 
prototype of this chip will be validated by a cell sorting operation.

Research institute

FEMTO-ST Institute is a joint research unit which is affiliated with the 
French National Centre of Scientific Research (CNRS), the University of 
Franche-Comté (UFC), the National School of Mechanical Engineering and 
Microtechnology (ENSMM), and the Belfort-Montbéliard University of 
Technology (UTBM). FEMTO-ST is active in different fields of engineering 
science: computer science, mechanics, optics and telecommunications, 
mechatronics, i.e. micro/nanorobotics and advanced control, 
time-frequency, energetics and fluidics. FEMTO-ST hires around 700 
persons, and is organized according to seven research departments. It 
also runs a microfabrication technology centre, which is recognized 
nation-wide, for mixing technologies from microelectronics and 

The thesis will be done in the AS2M Department, Automatic control & 
Micro-Mechatronic Systems. The research led in AS2M department deals 
with Automatic control, Robotics, Mechatronics and Industrial 
Engineering. This department has been working on microrobotics for more 
than fifteen years, notably for micro/nanomanipulation and assembly, 
development of components, systems and control methods to achieve tasks 
at the microworld. With around 30 persons involved in microrobotics, 
AS2M is the biggest team in the world on microrobotics and is usually 
involved in several European and national projects.
The department has knowledge on non-contact manipulation and on high 
speed trajectory control which will be exploited in this PhD. The 
candidate will get access to all the scientific equipment, including 
Finite Element Modeling software, micromanipulation platforms, clean 
room facilities, etc. He/she will get the opportunity to present his/her 
work in international conferences and journals.


The candidate should have a strong motivation for experimental work as 
well as for team work. Background in one of the following areas would be 
appreciated: robotics, control, micromechatronics, microfabrication. 
However, any application presenting a strong scientific background will 
be considered.

The candidate will work in a French laboratory, but the working language 
will be either French or English according to the candidate skills.


To apply, send a Curriculum Vita, a motivation letter and if available 
the master grades to:
michael.gauthier 'at' femto-st.fr
aude.bolopion 'at' femto-st.fr
before May, 12th 2015

Aude Bolopion
AS2M department - Femto-st Institute
24 rue Alain Savary, F-25000 Besançon, France
+33 (0)3 81 40 29 25

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