Supporting Online Material

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1 Supporting Online Material (A) Description of the suppleentary ovies Movie : Two-directional alignent of cells using 4-point electrodes % w/v yeast (S. cerevisiae) cells were assebled into D arrays using an AC electric field of 75 V and 30 Hz in the four-electrode chip. The gap between opposite electrodes was ~ 8. The ovie is taken over 30 in at frae in -. Movie : No structure foration in the absence of electric fields. A control test was perfored in which 0.08 % w/v yeast (S. cerevisiae) cells were allowed to sedient under gravity in the absence of electric field. No evidence of D array foration was found. The ovie is taken over 30 in at frae in -.

2 Movie 3: Experientally observed co-assebly of yeast cells and latex particles. 0. % w/v yeast (S. cerevisiae) cells ixed with 0. % w/v μ sulfate stabilized latex icrospheres were co-assebled between two parallel coplanar electrodes. The applied AC electric field was 0 V - and 30 Hz. This ovie has been speeded up 8. Movie 4: Nuerical siulation of the co-assebly dynaics of a two cell - two particle syste. D electrostatic siulations were perfored in FEMLAB to calculate the electric field distribution and cell-particle trajectories in the syste. The effective polarizability of yeast cells and μ latex spheres in DI water was calculated using our coputational procedure. The siulation shows how one of the latex icrospheres gets entrapped between the cells due to positive dielectrophoresis.

3 Movie 5: 3D anipulation of peranent cell ebrane. Freely suspended, one-cell layer thick, peranent yeast (S. cerevisiae) cell ebrane was anipulated in the external field of a sall agnet. This ovie is in real-tie. Movie 6: Folding of peranent cell ebrane. Peranent and onolayer thick yeast (S. cerevisiae) cell ebrane was folded in an external agnetic field. This ovie is in real-tie. 3

4 (B) Nuerical siulation details Suppl. Table. Nuerical paraeters for calculating effective polarizability of yeast (S. cerevisiae) cells. The values of these paraeters were taken fro efs. [, 3]. Cytoplas dielectric constant C J - - Cytoplas conductivity σ 0.5 S - Mebrane capacitance c 0.0 F - Mebrane transconductance g 0 S - Cell wall dielectric constant C J - - Cell wall conductivity σ 0. S - Inner radius Outer radius o Double layer thickness Δ Debye length κ Zeta potential ζ -30 V Counter-ionic layer dielectric constant EDL C J - - Counter-ionic layer conductivity σ s S - Mediu dielectric constant C J - - Mediu conductivity σ 0.07 S - Angular frequency ω 68 ad s - Effective cell dielectric constant C J - - Effective cell conductivity σ S - 4

5 Suppl. Fig.. (A) Multi-shell odel for the polarizability of yeast cell. (B) Siplified odel of yeast cell with effective polarizability equivalent to the ulti-shell type structure in (A). We developed a nuerical procedure for evaluating the effective polarizability of yeast cells as a function of frequency. In this odel, the ulti-shelled structure of the yeast cell was substituted by a hoogeneous sphere of coplex perittivity j '' = '' σ '' (Fig. B), the effective polarizability of which was equivalent to ω that of the original yeast cell (Fig. A). The procedure includes the following steps:. The coplex perittivities of the various shells coprising the yeast celxzl were expressed as follows: j Cytoplas: = σ () ω Mebrane: c j = c g () ω j Cell wall: = σ (3) ω Counter-ionic layer: EDL j = EDL σ s (4) ω 5

6 6. The coplex perittivities of the cytoplas and the ebrane were replaced with a hoogeneous sphere of equivalent coplex perittivity. 3. The coplex perittivities of the equivalent hoogeneous sphere in step and the cell wall were replaced with a hoogeneous sphere of equivalent perittivity. 4. The coplex perittivities of the equivalent hoogeneous sphere in step 3 and the thin counter-ionic layer were replaced with a hoogeneous sphere of equivalent coplex perittivity. The final expression for the coplex perittivity of the yeast cell in ters of the shell paraeters is given by equation (5). The values of each paraeter are given in Table. EDL o o = 3 3 ' ' ' ' ' ' (5) where, ' + = c c, EDL Δ = and ) exp( = kt ze o s ξ κ σ σ

7 Suppl. Table. Nuerical paraeters for calculating the effective polarizability of μ latex particles. The values of these paraeters were taken fro ef. [3] and fro the inforation data sheet provided by the producer, Interfacial Dynaics Corp. (O). Particle dielectric constant p C J - - Particle conductivity σ p S - Particle radius p Mediu dielectric constant C J - - Mediu conductivity σ 0.07 S - Surface charge density γ C - Sodiu ion obility μ Na S C - Particle surface conductivity σ s 0.0 S - Effective particle conductivity σ p 0.0 S - Suppl. Fig.. Models of latex icrospheres in aqueous edia: (A) Thin conductive counter-ionic layer surrounding the latex icrosphere. (B) Siplified structure with effective polarizability equivalent to the shell type structure in (A). 7

8 A odel siilar to the one described above for yeast cells was used to calculate the effective polarizability of latex particles in Fig. A. The equivalent conductivity of the siplified structure in Fig. B was given by equation (6). σ = σ + σ p ' (6) p s γ μ Na where σ =. s Force calculations for interactions between cells The spherical cells and particles were odeled in the D electrostatic calculations using FEMLAB as thin cylinders (or disks) with a height, h, coparable to the cell diaeter. We verified the accuracy of our nuerical procedure by coparing its results to the analytically calculated agnitude of the dipolar interaction force between two cells. The analytical forula for dipolar interaction between spherical particles, F chain = Cπ E K (where, 3 3 < C < 0 ), was odified to F chain = Cπ E h K. Here, h is the height of the cylinder and C depends on the relative positions of the two cylinders. The nuerical and analytical values for the dipolar attraction between two cells at different positions are given in Table 3. We assue h = in these calculations. The results correlated very well for the cases when the cells are separated by distances greater than ~ 0.5 but a deviation of - orders of agnitude occurred when the cells were positioned very close to each other. This deviation is expected because the analytical 8

9 calculations do not account for the higher order utual polarization effects that becoe significant at sall interolecular distances and strongly increase the attraction. The velocities of the cells after accounting for the hydrodynaic resistance were obtained to be of the order of ~ μ s -, which corresponds well to the experiental data. These results suggest that the odel correctly captures the dynaics and agnitudes of forces involved in the cells assebly process. Suppl. Table 3. Force calculations for interactions between cells. Coparison between nuerical and analytical values obtained for dipolar forces between yeast cells at two different positions. Dipole Interaction Nuerical Calculations F Nu = E. D +. S ( n E) D T ds F Anal Analytical Calculations = C π E c h e c N N N N 9

10 (C) Other suppleentary data Suppl. Fig. 3. Effect of applied AC electric field on the cell chain length. The dielectrophoretic response of 0. % w/v yeast (S. cerevisiae) cells was easured by systeatically varying the voltage and frequency of the electric field between two coplanar parallel gold electrodes. The electrode gap was ~ 3. 0 optical icrographs were taken at different parts of the saple exactly in after tunring on of the electric field. The nuber of cells was counted using Iage Pro software (Media Cybernetics; Bethesda, MD). The results for each experient were reported as an average of the data fro ten iages. The data prove that longer chains are fored at higher voltages and lower frequencies. 0

11 Suppl. Fig. 4. Cell viability tests. (A) Yeast (S. cerevisiae) cells were stained with FUN- dye and assebled into chains using 0 V - and 00 Hz AC electric field. The etabolic activity of cells is indicated by the orange-red fluorescent intravacuolar structures in the cytoplas when viewed using fluorescence icroscopy (inset). The icrograph shows that ost cells stay alive during the assebly process. (B) NIH/3T3 ouse fibroblast cells were stained using Trypan Blue dye and aligned in 0 V - and 0 khz AC electric field. Cells that do not appear blue in transitted-ode optical icroscopy are viable (inset). These results show that the viability of ost fibroblast cells is unaffected by the electric field.