In cooperation with the technical team of the caesar we successfully scaled-up the bandwidth of the electrical actuator system, continuing the previous activity started in year 3 making use of the advanced clean room facility at Chalmers, i.e. the Department of Microtechnology and Nanoscience, as also supported by the EU-project: "MC2Access".
We integrated multilayer metallization (with crossover wires and vias) into our existing fabrication procedures with Si-PDMS electronic-microfluidics. This leads to a significant enhancement of the density of electrode control structures for the parallel control of artificial cells and other complex chemical systems. The previous design of the chip contained 288 single controllable microelectrodes. The changeover to the new multilayer electronic chip design (based on basic FPGA 80 inputs), we have increased the integration density from the previous single layer design from 288 to 5.338 electrodes for the same chip space (2.3 cm2) arranged in approx. 74 blocks containing 72 individual controlled electrodes each.
The fabrication process starts with a lithographic step to structure the first conducting layer containing electrodes, wires and the vias for the upper (2nd) electrode layer. The following steps are a passivation layer (SiO2) deposition and a second Ti/Au metallization process (e.g. sputtering, vapour deposition) and an etching procedure to realize the upper electrodes and wires and to complete via connections. After opening the 2nd passivation layer at the electrode and conducting pad areas I/O holes were placed using deep etching of the silicon substrate by Inductively Coupled Plasma (ICP) to allow a reverse side fluidic connection. The final steps are soft-lithography fabrication of PDMS micromoulds, which consist of an array of microfluidic channels as well as bonding the components using oxygen plasma.