Cytokine secretion assays provide the means to quantify intercellular-signaling proteins secreted by blood immune cells.
These assays allow researchers and clinicians to obtain valuable information on the immune status of the donor.
Previous studies have demonstrated that localized surface plasmon resonance (LSPR) effects enable label-free, real-time
biosensing on a nanostructured metallic surface with simple optics and sensing tunability. However, limited sensitivity
coupled with a lack of sample handling capability makes it challenging to implement LSPR biosensing in cellular
functional immunoanalysis based on cytokine secretion assay. This paper describes our recent progress towards full
development of a label-free LSPR biosensing technique to detect cell-secreted tumor necrosis factor (TNF)-α cytokines
in clinical blood samples. We integrate LSPR bionanosensors in an optofluidic platform capable of handling target
immune cells in a microfluidic chamber while readily permitting optical access for cytokine detection.
High-speed, high-resolution, miniature photospectroscopy techniques suited for a microfluidic platform
enable rapid, cost-effective and efficient assays for use in the clinic, or home, in the field with emergency
medical personnel, or on biochemical production lines. We demonstrated an innovative MEMS tunable
diffraction grating implemented for spectroscopic measurements requiring simple optics and signal processing. The
device is composed of a polydimethylsiloxane (PDMS) microbridge with a nanoimprinted grating pattern on the top
surface. MEMS silicon comb drive actuators mechanically strain the microbridge in order to variably tune the grating
period. Our innovative nano photonic technology incorporating the tunable grating may guide future
advancements of wavelength-discriminating detection for the identification and quantification of chemical
and biological species.
This paper reports a new microfabrication process named "Multi-Scale Soft-Lithographic Lift-Off and Grafting (MS-SLLOG)" used to construct active nanophotonic devices. MS-SLLOG is a low-temperature (less than 150°C) microfabrication technique that allows soft lithographically molded polymer micro-structures to be integrated together with silicon-based microelectromechanical systems (MEMS) structures to perform active control. Moreover, MS-SLLOG process allows us to achieve a hierarchical device structure seamlessly accommodating feature sizes ranging from tens of nanometer to sub-millimeters on a single chip for nanophotonic structure integration. To demonstrate the MS-SLLOG process capability, a strain-controlled micro-optical grating device is fabricated and experimentally characterized. The experimental results successfully show the operation of an active polymer nanophotonic device fabricated by the MS-SLLOG process.
This paper reports on a new micro optical reflector made of an organic elastomer, Polydimethylsiloxane (PDMS), which achieves multi-axis motion with a single actuator layer. The whole device structure incorporates Au-coated three-dimensional PDMS micro reflector integrated with electrostatic MEMS actuators on a silicon chip by a new fabrication method named "Soft-Lithographic Lift-Off and Grafting (SLLOG)" process. The SLLOG process is a low-temperature (less than 150°C) microfabrication technique that allows soft lithographically molded PDMS micro-structures to be integrated together with silicon micromachined device patterns. The developed PDMS/silicon hybrid device reflects visible light with fast response and large rotational motion through taking advantage of the mechanical compliance of PDMS structures. The demonstrated PDMS-based reflector can achieve 4.6 micron vertical displacement using AC actuation voltage of 40 V at frequency of 1.0 kHz, and ±1.43° scanning angles using AC actuation voltage of 40 V at resonant frequency of 5.0 kHz, and ±0.85° scanning angles for static operation at 60V.
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