Polymer Microlens Array
Microlens arrays have been widely used as essential components in many optical systems, including digital display, integral imaging, high-density data storage, and optical communications. In particular, the integration of microlens arrays with micro-light-emitting diodes (µ-LEDs) has become a promising solution to implanting light sources for applications that require high-resolution multisite illumination, for example, the rapidly progressing field of optical neural stimulation. We are developing novel polymer processing techniques for constructing microlens arrays in a rapid and cost-effective way. As an example, we have developed a vapor-induced, low-temperature dewetting process, which enables the formation of SU-8 microlens arrays on pre-patterned, heterogeneous polydimethylsiloxane substrates.
Project Participant: Xiaopeng Bi
Polymer Microneedle Array
Microneedles based on microelectromechanical systems technologies can be utilized as an interface between an organic system and an external micro device, for either delivering a liquid substance such as a drug, protein, or nano-particles into the organism, or extracting biofluids from the organism for analysis. In addition, microneedles can be used as microelectrodes to interface with the nervous system for neural recording and stimulation. In this project, we have demonstrated a single-step backside ultraviolet lithography method, namely droplet backside exposure, for making slanted microneedle structures monolithically on a flexible polymer substrate. The length of the microneedles can be controlled precisely by tuning the volume of the SU-8 droplet, utilizing the wetting barrier phenomenon at a liquid-vapor-hydrophilic surface-hydrophobic surface interface.
Project Participant: Dr. Ki Yong Kwon
Intraocular Pressure Sensor
Glaucoma is a degenerative eye disease that is usually associated with elevated intraocular pressure (IOP) due to abnormally high production and/or retention of aqueous humor. Currently my group is developing a variety of flexible, highly responsive wireless intraocular pressure sensors for glaucoma management. Typically the sensor is comprised of an integrated planar MEMS coil and a variable capacitor. The devices are manufactured using polymer-based micromachining techniques. Current devices have achieved minimum and average pressure responsivities of 200 kHz/mmHg and of 490 kHz/mmHg in air and 200 kHz/mmHg and of 320 kHz/mmHg in water over a range of 0 to 100 mmHg. A maximum detection distance of 20 mm has been achieved in isotonic saline.
Project Participants: Brian Crum, Yue Guo