Armin Werber

Tunable microfluidic microlenses

A novel type of liquid microlens, bounded by a microfabricated, distensible membrane and activated by a microfluidic liquid-handling system, is presented. By use of an elastomer membrane fabricated by spin coating onto a dry-etched silicon substrate, the liquid-filled cavity acts as a lens whereby applied pressure changes the membrane distension and thus the focal length. Both plano-convex and plano-concave lenses, individual elements as well as arrays, were fabricated and tested. The lens surface roughness was seen to be approximately 9 nm rms, and the focal length could be tuned from 1 to 18 mm. This lens represents a robust, self-contained tunable optical structure suitable for use in, for example, a medical environment.

Tunable Pneumatic Microoptics

A new class of tunable and actuated microoptical devices is presented: pneumatic microoptics. Using microelectromechanical system fabrication technology extended by the use of polydimethylsiloxane (PDMS) membranes, tunable microlenses, and lens arrays, actuated micromirrors with large tilt angles and tip-tilt piston mirrors have been designed and fabricated. Actuation is by pressure: Gas- or liquid-filled microfluidic cavities are employed to distend the microfabricated PDMS structures which then act as a lens surface or as an actuator for a micromirror. Thermopneumatic actuation is also employed for completely integrated tunable optical systems in which all actuator and optical components are fabricated on-chip. The technology is particularly promising for microsystem applications in which significant movement is required but high voltages or external fields are impractical. [2007-0301].

Fiber optic tunable probe for endoscopic optical coherence tomography

A novel miniaturized fiber optic tunable endoscopic probe based on a pneumatically actuated micro-lens is presented. The probe has a diameter of ∼4 mm and is integrated into a time-domain optical coherence tomography (OCT) system. The integration of the tunable lens with the OCT system leads to a uniformly high lateral resolution and high contrast of the OCT images over the entire scan depth. In addition, the tunable probe can be considered as a platform for integrating multiple microsystems, including particularly scanning micro-mirrors, in a single high-performance endoscopic OCT system.

Thermo-pneumatically actuated, membrane-based micro-mirror devices

A novel design for thermo-pneumatically actuated, membrane-based micro-mirror devices, using an elastomer membrane fabricated in a spin-coating process on a dry-etched silicon substrate, is presented. The silicon mirror devices are etched from the substrate and fixed to the highly elastic 50 µm thick membrane and actuated by thermo-pneumatic pressure. This pressure is generated by a micro-hotplate bonded to the backside of the silicon substrate. Such devices provide strokes from 0 to 80 µm and tilting angles in the range from 0° to 13°, relative to the substrate surface. Thermo-pneumatic actuation achieves large angle and stroke deflection, making this approach suitable for a large array of applications. Tilting mirrors, piston mirrors as well as mirror arrays have been realized using this technology.

Sealing method of PDMS as elastic material for MEMS

This paper proposes an effective sealing method of PDMS (polydimethylsiloxane) without losing elasticity of the material. Parylene (poly-para-xylylene) CVD can caulk porous PDMS structure and provide low permeable characteristics. The longstanding drawback is that parylene deposition on PDMS spoils elastic features of PDMS. MEMS devices using deformation of PDMS such as micro pump and micro balloon actuator requires not only high sealing but also high elasticity of PDMS. Deposited parylene permeates PDMS and then forms a film on PDMS. Our key idea is to remove a surface parylene layer on PDMS with the aim of keeping elastic features of PDMS. O2 plasma etching is applied to remove unnecessary surface parylene. This paper evaluates sealing and elastic features of parylene-caulked PDMS. Componential analysis of provided material by FTIR spectrum (FT-720, HORIBA Inc) is also reported. Parylene-caulked PDMS is applied to pneumatic balloon actuator devices, PDMS membrane-based micro-mirror device, in order to demonstrate advantages of proposed method.

Development of an Implantable Pulse Oximeter

A long-term implantable photoplethysmographic sensor system is proposed. The system employs an elastic cuff which is directly wrapped around an arterial blood vessel. The optically transparent cuff is equipped with light emitting diodes and a photo transistor including the technology of pulse oximetry. The sensor will permit real-time, continuous monitoring of important vital parameters such as arterial blood oxygen saturation and pulse rate over a long-term period in vivo. We emphasize on the specific requirements for design and instrumentation of the implantable sensor and discuss first in vitro data acquired with that new photonics-based sensor.

Tunable, membrane-based, pneumatic micro-mirrors

A novel design of tunable, membrane-based micro-mirrors is presented. The micro-mirror is actuated by pneumatic pressure which provides large deflection and a large range of angle from -10deg to 70deg, relative to the substrate surface

Tunable, membrane-based, liquid-filled micro-lenses

A novel type of liquid microlens, bounded by a microfabricated, distensible membrane and activated by a microfluidic liquid-handling system, is presented. Using an elastomer membrane fabricated by spin-coating on a dry-etched silicon substrate, the liquid-filled cavity acts as a lens whereby applied pressure changes the membrane distension and thus the focal length. Both plano-convex and plano-concave lenses, individual elements as well as arrays, were fabricated and tested. Lens surface roughness was seen to be about 9 nm rms and focal length could be tuned from 1 to 18 mm. This lens represents a robust, self-contained tunable optical structure suitable for use in, for example, a medical environment.

A Thermo-Pneumatically Actuated Tip-Tilt-Piston Mirror

We present a novel, high stroke tip-tilt-piston micro-mirror actuated by thermo-pneumatic forces. A circular silicon mirror plate is mounted on top of three balloons, made of a 50 mum thick elastomer membrane. The balloons are inflated under thermo-pneumatic pressure, thus driving the mirror plate into tip-tilt and piston motion. Very large stroke values of 385 mum as well as tip-tilt angles of 5deg were measured. The triangular arrangement of the balloon actuator yields a high flexibility in mirror motion, including tip-tilt in any direction.

Tunable Endoscopic MEMS-Probe for Optical Coherence Tomography

A novel miniaturized tunable endoscopic MEMS probe employable in an endoscopic optical coherence tomography (OCT) system is presented. The probe consists of a pneumatically-actuated micro-lens and a GRIN lens coupled to an optical fiber. Silicon micromachining using polydimethylsiloxane was used to fabricate the lens. The probe has a diameter of 5 mm. The successful integration of the tunable endoscopic probe with an OCT imager promises to be of value in medical diagnostics, particularly for the early detection of internal tumors and cancers.