Figure 1

Design of portable single-cell microchip system.

(a,b) Features on the PDMS replica with corresponding dimensions. (c) Scheme for the fabrication of a 4-layer microchip mold using SU-8 2015, 2025, 2100 and SPR220 photoresists. Four layers of photoresists are stacked on one another and carefully aligned during the fabrication process on a 4″ silicon wafer. The bottom layer at a thickness of 100 μm is used as the base for all the other layers, which is translated to be the PDMS horizontal. Once it is developed following standard photolithography protocol, the second layer for ducts made of SPR 220 photoresist is fabricated on the previous layer. Similar procedures are followed for adding the third and the fourth layers corresponding to cell chambers and channels, respectively. While the features on all four layers are distinctive, only the posts on the photomasks are hollowed out and aligned throughout all layers, resulting in long PDMS posts with a height of 150 μm after casting. (d) Microchip mold on a silicon wafer showing cell chamber arrays connected to microchannels in a grid design (scale bar = 500 μm). (e) Diagram of the whole stand-sit chip (SSC). All the features on PDMS are fabricated together from one mold, which avoids the downstream multistep alignment for constructing multilayer PDMS devices in most single cell microchips and simplifies the microchip fabrication process as well as operation process. (f ) Mechanical clamp system for the operation of the SSC showing the adjustment screw to vary the external forces to switch between chip states and pipette tips connected to the inlets and outlets.