Faculty Bibliography

Bifunctional nanoarrays were created to simulate the immunological synapse and probe the T-cell immune response at the single-molecule level. Sub-5 nm AuPd nanodot arrays were fabricated using both e-beam and nanoimprint lithography. The nanoarrays were then functionalized by two costimulatory molecules: antibody UCHT1 Fab, which binds to the T-cell receptor (TCR) and activates the immune response, bound to metallic nanodots; and intercellular adhesion molecule-1, which enhances cell adhesion, on the surrounding area. Initial T-cell experiments show successful attachment and activation on the bifunctional nanoarrays. This nanoscale platform for single-molecule control of TCR in living T-cells provides a new approach to explore how its geometric arrangement affects T-cell activation and behavior, with potential applications in immunotherapy. This platform also serves as a general model for single-molecule nanoarrays where more than one molecular species is required.

Micromachined viscometric affinity glucose sensors have been previously demonstrated using vibrational cantilever and diaphragm. These devices featured a single glucose detection module that determines glucose concentrations through viscosity changes of glucose-sensitive polymer solutions. However, fluctuations in temperature and other environmental parameters might potentially affect the stability and reliability of these devices, creating complexity in their applications in subcutaneously implanted continuous glucose monitoring (CGM). To address these issues, we present a MEMS differential sensor that can effectively reject environmental disturbances while allowing accurate glucose detection. The sensor consists of two magnetically driven vibrating diaphragms situated inside microchambers filled with a boronic-acid based glucose-sensing solution and a reference solution insensitive to glucose. Glucose concentrations can be accurately determined by characteristics of the diaphragm vibration through differential capacitive detection. Our in-vitro and preliminary in-vivo experimental data demonstrate the potential of this sensor for highly stable subcutaneous CGM applications.

A novel shock switch based on a micro-electro-mechanical system (MEMS) for vibration monitoring was designed and fabricated by non-silicon surface micromaching technology. It consisted of three main parts: the proof mass as the movable electrode, the cross beam as the stationary electrode and the movable contact point to prolong the contact time. The ANSYS model was built, by which the modal analysis was carried out showing that the new design reduced the sensitivity to off-axis accelerations compared with the previous design, and the physical parameters were extracted from the structure so they could be used in the Simulink model. Through the dynamic simulation, the contact-enhancing mechanism was verified and compared with the traditional design. The fabricated micro shock switch was tested with a dropping hammer experiment. Test results indicated that the threshold acceleration was about 145 g and a stable contact time of over 50 μs was observed under a half-sine wave shock load acceleration with 1ms duration, in agreement with the simulation results. The contact effect was improved significantly as expected and the proposed model was able to describe the device's behavior correctly.

Based on non-silicon surface micromachining technology, a simple but reliable micro electro-mechanical system (MEMS) electrical inertia micro-switch with single sensitive direction and reverse impact protection is designed and fabricated on glass substrate. In this design, conjoined serpentine springs are used to fix and suspend the mobile electrode (mass) and blocks are used to protect the device against reverse impulse. The switch is laterally driven (i.e. its sensitive direction is parallel to the substrate). Fabrication is carried out by low-cost and convenient multi-layer electroplating technology. The relationship between threshold acceleration and mass thickness has been investigated by theoretical analysis and finite element analysis (FEA) simulation. After fabrication and packaging, micro-switches are tested by using drop weight. The results show that the threshold accelerations distribute between 58 g and 72 g, which basically fulfils the expected 60 g; and the response time to 100 g half-sine waved shock is in the order of 10^-4 s, which is in agreement with simulation result.