Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mobile Microelectrodes: Towards active spatio-temporal control of the
  electric field and selective cargo assembly   With an eye towards next-generation, smart, micro/nanofluidic devices,
capable of responding to external stimuli or changes in environment, we
demonstrate a means to achieve dynamic control of the spatio-temporal
properties of the electric field in a standardized microfluidic chamber.
Typical top-down patterning, currently used to design the field distribution,
is replaced by freely-suspended colloids which locally disturb the electric
field from the bottom-up. Even under uniform forcing, polarization of the
colloid induces the formation of strong, three-dimensional gradients at its
surface - essentially repurposing it into a portable floating electrode whose
precise location can be manipulated to reconfigure the electric field in real
time. Focusing on active Janus colloids as a sample platform, we measure the
strength of the induced gradients and highlight the advantages of a
colloid-based system by revealing a prototype for an all-in-one cargo carrier,
capable of on-demand, selective, label-free assembly and transport of
micro/nano sized targets.

16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex