Cell-Based Chips for Biotechnology - Introduction to BioMEMS - page 259

Electrode

a b

Anchors

10 µm

Tunnels

50 µm

R spread

c Neurocage wall

(insulating)

R cage + R spread = 25 kΩ
C elec = 4300 pF
C shunt = 20 pF
Z s hunt = 3.5 MΩ

R cage

Z shunt

C elec

To stim/amplifiers

FIGURE 5.16 “Neuro-cages”. for. extracellular. recording. from. in. vitro. neural. networks.. (From.
Jonathan.Erickson,.Angela.Tooker,.Y.-C..Tai,.and.Jerome.Pine,.“Caged.neuron.MEA:.A.system.for.
long-term. investigation. of. cultured. neural. network. connectivity,”. J. Neurosci. Meth. . 175,. 1-16,.
2008..Reprinted.with.permission.from.Elsevier.)

Microluidics can be used in combination with microwells to selectively “dock” cells to
designated microwells or groups of microwells. In the simplest coniguration possible, Robert
Langer's group at MIT devised simple linear microchannels to address rows of microwells (a dif-
ferent cell type on each row), then turning the microchannels orthogonally addressed the array
by columns ( Figure 5.18 ). However, this approach does not allow for individually addressing
each microwell. Recently, Joel Voldman and colleagues at MIT have devised a laser-levitation
method to extract selected cells from microwells: the laser is focused onto the cells through the
microscope objective from underneath so as to counteract gravity, and the photons' momentum
is suicient to lit the cell out of the well, at which point it is taken away by the low.

25 micron wells 35 micron wells 40 micron wells

FIGURE 5.17 Cell. trapping. in. PDMS. microwells.. (From. Rettig,. J.. R.. and. A.. Folch,. “Large-scale.
single-cell. trapping. and. imaging. using. microwell. arrays,”. Anal. Chem. . 77,. 5628,. 2005.. Figure.
contributed.by.Jackie.Rettig.)