Overview of biosensors

Optical-fiber sensors can be used to perform difficult measurement in situations where the use of conventional sensors is not practical. The sensors are usually compact and lightweight, minimally invasive, and can be multiplexed. They are immune to electromagnetic interference, and can survive in difficult environments. The need to measure various analytes simultaneously has led to the development of optical sensor arrays for capturing a full chemical profile of the sample being measured. For example, multiple sensing chemistries may be attached to the end of optical fibers in a fiber bundle and different sensing chemistries may be identified by either spatial or spectral resolution.

Biosensors

Ink-jet technology was used to print one or more indicator chemistries on optically accessible surfaces. An example of such a surface is the tip of an optical fiber. The method provides a means of precisely printing many different materials in a given pattern using a wide variety of MJ dispensing device geometries. Each indicator chemistry may contain one or more light energy absorbing dye(s) whose optical characteristics change in response to the target analyte.

Biosensor lenses printed on the end of a optical fiber bundle.

By spectrally monitoring (fluorescence spectroscopy) the characteristics of each sensors, sensitive detection and quantitation of the target analyte can be obtained. Simultaneous detection and measurement of these analytes can be performed by optical imagining methods to spatially register each printed microdot.

Schematic diagram of a microphotometer that uses fluorophor dyes printed on the fiber optics tip. Prototype in the figure below.

Prototype microphotometer built at Lawrence Livermore National Labs using sensing elements printed at MicroFab Technologies [Image courtesy of LLNL].

Ink-jet technology can be used together with other technologies in packaging and fabrication of bio-MEMS components such as: microlenses, microlensed fiber optics tip, or electronics boards (solder deposition for microptical interconnects). A schematic of such a MEMS optical bench is shown in the figure below.

Schematic of packaging a MEMS optical bench (total dimension <1").

The components that can be used in a MEMS optical assembly are shown below. For example, a metallic MEMS method is used to fabricate clampers for passive alignment, which has a lower labor cost than the active alignment in fabrication. The clamped VCSEL array is also shown in the figures below. Different clampers can be processed on a same wafer to form an optical bench.

Metallic MEMS clamper for passive alignment of opto-electronic chip.	Jetted microlenses.
Lensed VCSEL array aligned to the opto-electronic chip using the clamper in the figure above. Lenses on top of the posts printed at MicroFab.	Processed wafer containing multiple clampers.

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