Joe L. Gonzalez

Fabrication of and cell growth on ‘silicon membranes’ with high density TSVs for bio-sensing applications

A silicon membrane acting as an interface layer between live cells and the sensing electronics enabling low-cost, high-throughput bio-sensing is proposed; the interface is capable of supporting high pixel density allowing accurate image mapping. Cell attachment and growth was carried out on five different silicon based surfaces and compared to the standard Tissue Culture Polystyrene (TCPS) surface in order to optimize the selection process of the interface material; cell imaging is performed after 48 hours to study the effect of different surface variations (different materials on silicon, presence of metal, increased surface roughness due to CMP, etc.) on cell adhesion and growth. The results show that cells successfully adhere and grow onto the sensing electrodes for all the surfaces under test after the first 48 hours. Key enabling technologies for high pixel density membranes are also presented.

3-D Integrated Electronic Microplate Platform for Low-Cost Repeatable Biosensing Applications

This paper presents a 3-D integrated disposable “electronic microplate” (e-microplate) platform that allows the reuse of CMOS biosensor, thereby significantly reducing cost and increasing throughput compared to nondisposable biosensing systems. The e-microplate utilizes mechanically flexible interconnects and through-silicon-vias to electrically connect the cells cultured on the top (sensing electrode side) of the e-microplate to the electrodes on the CMOS biosensor while maintaining a physical separation between the aforementioned substrate tiers. Electrical measurements performed show that the incorporation of the e-microplate does not degrade the sensing amplifiers gain, 3-dB bandwidth, or the input referred noise; this ensures a high signal-to-noise ratio allowing accurate sensing of weak signals from living cells under test. Cell growth experiments performed show adhesion and growth of mouse embryonic stem cells on the surface of the sensing electrodes of the e-microplate. Impedance mapping for Dulbeccos phosphate buffered saline solution performed with the e-microplate, for two different e-microplate assemblies, confirms the functional accuracy of the assembled systems.

Dense and Highly Elastic Compressible MicroInterconnects (CMIs) for Electronic Microsystems

In this paper, dense, highly elastic compressible microinterconnects (CMIs) are presented as an enabling technology for next generation sockets, probe cards and heterogeneous integrated systems. Free-standing CMIs with 75 µm height are fabricated using a thick sacrificial photoresist layer with an upward curved sidewall profile. The CMIs show a 45 µm vertical elastic range of motion. The fabricated CMIs have an in-line pitch of 150 µm, mechanical compliance of 9.2 mm/N, and vertical elastic motion of up to 5,000 indentation cycles. The smallest in-line pitch of CMIs demonstrated is 40 µm. The average post-assembly resistance of the CMIs, including the contact resistance, was measured to be 176.3 mΩ.