(257n) Micro-scale cell patterning based on tunable CO2 laser system

Micro-scale cell
patterning based on tunable CO₂ laser system

Wenjun
Zheng, Sichao Hou, Ming Su^*

Department of Chemical Engineering, Northeastern
University, Boston, MA 02115

Since
cell patterning on 2D surfaces has emerged as an effective tool in cell
biology, the development of easy patterning methods has attracted great attention.
The lithography approaches, for instance photolithography and micro-contact
printing, are often used for small scale pattering. Photolithography uses ultraviolet (UV) light to transfer a geometric pattern from a photomask to a light-sensitive chemical (photoresist)
on the substrate. For micro-contact
printing, an elastomeric stamp (Polydimethylsiloxane) forms patterns on the surface of substrate through conformal,
transient contact. However, major issues of existing cell patterning methods are
the strict operating conditions and the relatively complicated procedure without
a matched accuracy. In this work, an easily operated, non-contact and high
throughput method to produce micro-scale pattering with a tunable laser cutting
machine is introduced.

Glass substrate was used to test the impact of parameters,
including laser power (3~15W) and laser speed (7.7~20.0 mm/s), on the line
width. The result indicated that the line width increased with the laser power
and followed the Gaussian Equation. Specially, for small laser power
(<5.0W), the increase of the line width with the laser power followed a
linear relationship. A 2D theoretical modal was built to simulate the heat
transfer in the laser cutting process. The simulation result indicated the laser
penetration depth on glass substrate was independent of the laser speed, which was
further used to predict the line width at the speed of 25.0 mm/s. The relative
error between the experimental and simulated results is less than 2.0%. The
prediction of line width on the polystyrene petri dish with a laser power
ranged from 0.9~3.3W was conducted using the acquired model and the values of
the parameters were deduced for a line width of 150 μm,
based on which a pattern was machined for 2D cell patterning. This work
demonstrates that the micro-scale patterning with a laser cutting machine is a
promising method for refined cell coordinator and accurate cell positioning.

Figure 1. Schematic presentation of the
laser cutting mechanism (A) and the 2D theoretical heat transfer model for
laser cutting process (B). The line width was predicted using the theoretic
modal (C).

Acknowledgement

This work was supported by the Department of
Chemical Engineering, Northeastern University.