Sensors & Actuators
20 matches found.

Implantable Wireless Dosimeters for Radiation Oncology

T. Maleki, C. Son, B. Ziaie

We present the development of two radiation detectors for accurate dose monitoring in radiation oncology. The first one is a passive MEMS-based miniature ionization chamber for total accumulated dose measurement. A sensitivity of 49 kHz/Gy in a dynamic range of 30 Gy was achieved in an LC configuration. The second transducer is based on a sensitive solid-state structure that can be used in active interrogation schemes. This sensor exhibited a sensitivity of 50 k¿/Gy in a dynamic range of 20 Gy.


A Batch-Fabricated Laser-Micromachined PDMS Actuator with Stamped Carbon Grease Electrodes

We report on the development of a batch-fabricated laser-micromachined elastomeric cantilever actuator composed of a polydimethylsiloxane (PDMS) bilayer (active/inactive) and soft-lithographically patterned conductive carbon grease electrodes. The described unimorph structure has a low actuation voltage and large out-of-plane displacement. For a 4 mm long, 1 mm wide, and 80 µm thick actuator, an out-of-plane displacement of 1.2 mm and a maximum force of 25 µN were measured using 450 V actuation voltage.


Ferrofluid-Impregnated Paper Actuators

Ferrofluid - Paper

we report on an inexpensive method of fabricating miniature magnetic actuators using ferrofluid impregnated paper. Different types of papers (including soft tissue paper, cleanroom paper, Whatman-1 filter paper, printer paper, and newspaper) were loaded with oil-based ferrofluid, microma-chined by a CO2 laser and coated with a thin layer of parylene-C. The soaking capability of the different papers was investigated, with the soft tissue paper having the highest loading capacity, being able to absorb ferrofluid by as much as six times its original weight. Cantilever actuators fabricated from cleanroom and filter papers were able to generate the largest force (>; 40-mg equiva lent force), whereas the soft-tissue-paper cantilevers provided the greatest deflection (40° tip angle).



G. Chitnis, B. Ziaie

This paper presents a novel minimally invasive implantable pressure sensing transponder for continuous wireless monitoring of intraocular pressure (IOP). The transponder was designed to make the implantation surgery simple while still measuring the true IOP through direct hydraulic contact with intra-ocular space. Furthermore, if situation demands (e.g., malfunction), implantation site allows physicians to easily retrieve the transponder. The device consists of three main components: 1) a hypodermic needle (gauge 30) penetrating sclera through pars plana and establishing a direct contact to the vitreous humor, 2) a micromachined capacitive pressure sensor connected to the needle back-end, and 3) a flexible polyimide coil connected in parallel with the capacitor forming a parallel LC circuit whose resonant frequency is a function of IOP. Most parts of the sensor sit externally on the sclera and only the needle penetrates inside the vitreous space through pars plana. In vitro tests showed a sensitivity of 15 kHz/mmHg with about 1 mmHg resolution. One month in vivo implants in rabbits confirmed biocompatibility, robustness, and functionality of the device.


Hydrogel-based microsensors for wireless chemical monitoring

M. Lei, A. Baldi, E. Nuxoll, R. A. Siegel and B. Ziaie

We report fabrication and characterization of a new hydrogel-based microsensor for wireless chemical monitoring. The basic device structure is a high-sensitivity capacitive pressure sensor coupled to a stimuli-sensitive hydrogel that is confined between a stiff porous membrane and a thin glass diaphragm. As small molecules pass through the porous membrane, the hydrogel swells and deflects the diaphragm which is also the movable plate of the variable capacitor in an LC resonator. The resulting change in resonant frequency can be remotely detected by the phase-dip technique.