Fabrication of a pneumatically driven single-cell trap Tae Kyung Kim, Ok Chan Jeong ⇑ Department of Biomedical Engineering, Inje University, Gimhae 621-749, South Korea article info Article history: Available online 30 November 2010 Keywords: Single cell Trap Pneumatic vibrator Intracellular calcium abstract This paper describes the creation of a pneumatically driven single-cell trap and its ability to trap a live single cell. The cell-trap device consists of a pneumatic vibrator array and a trap chamber used to trap single cells. The entire structure was manufactured with polydimethylsiloxane (PDMS). External com- pressed air was used to actuate the pneumatic vibrators. The magnitude and frequency of the pneumatic force were controlled by programmable electromagnetic valves. The live cell in the trap chamber was manipulated using the velocity field of the cell media induced by deformation of the vibrator diaphragm. The cell was successfully trapped in the central equilibrium region of the device, at which point the axial velocity fields generated by the vibrators were minimized. The intracellular calcium response of a single cell induced by mechanical stimuli during cell trapping was measured to verify the effectiveness of the pneumatic cell trap as a stress-free trapping method. The results showed that the internal signaling in the cell was sensitive to the extracellular physical environment. Since the measured intensity of the intra- cellular calcium of the single cell was very minor, the pneumatic cell trap described in this paper was cat- egorized as a harmless trapping method. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Cell-handling devices using micro machining techniques have garnered attention in recent years with regards to investigating true phenomenon and cellular information on the scale of a single cell. Cell studies with large populations of cells can only obtain average values of the cellular response for many types of cells [1]. Thus, many kinds of useful and versatile cell trapping and separation methods have been developed, such as dielectrophoretic [2], laser [3], acoustic [4], magnetic [5], and pneumatic [6] techniques. These techniques are categorized as contactless immobilization tech- niques, with each method having its own advantages and disadvan- tages [7]. These recent studies on existing cell handling devices have mainly focused on the operation method, the creation of the corre- sponding devices, and characterization. One of the important over- looked points is related to stimuli effects in the trapped cells due to the operational method. In Ref. [8], mechanical stimuli are posi- tively used to differentiate human mesenchymal stem cells. How- ever, in the case of cell traps, stimulation effects should be excluded in order to trap healthy and normal cells. Cells in micro- fluidic chips could be stimulated by unwanted factors induced by the operational method, such as thermal and mechanical stresses [1]. A more sophisticated cell-handling device is required that considers the effect of stimulations on the cell carefully by changing the external cellular environment when the cell is trapped. This paper presents a live cell-trap device with a pneumatic vibrator to realize a gentle cell trap that does not exert any thermal or electrical stimulation influence on the trapped cell. The device uses fluid flow, and was fabricated with only polydimethylsiloxane (PDMS) using soft lithography. The intracellular calcium response of a cell was measured to study the influences of mechanical stim- uli on a live cell during its trapping. 2. Device and operational method 2.1. Structure Fig. 1 illustrates a schematic view of the pneumatically driven cell-trap unit. The device consists of three PDMS layers: the interconnection layer (I) for the external compressed air and to introduce the cell/media, the vibrator layer (II) to act as the pneu- matic actuator for the cell trapping, and the chamber layer (III) for the cell/media. After the fabrication process, the chamber is filled with cell media as fluid film. Three photo masks are used to fabricate SU8 molds for soft lithography. After creating the three PDMS layers, the vibrator and chamber layers are first bonded together, and then this structure is bonded again with the interconnection layer. 2.2. Operational method Fig. 2 shows the velocity field of the fluid induced by the deformed PDMS vibrators when 125 kPa of compressed air is sup- plied to the four vibrators. The diameter of each vibrator is 100 lm, 0167-9317/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2010.11.050 ⇑ Corresponding author. E-mail address: memsoku@inje.ac.kr (O.C. Jeong). Microelectronic Engineering 88 (2011) 1768–1771 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee