We review efforts to produce microfabricated glucose sensors and closed-loop insulin delivery systems. These devices function due to the swelling and shrinking of glucose-sensitive microgels that are incorporated into silicon-based microdevices. The glucose response of the hydrogel is due to incorporated phenylboronic acid (PBA) side chains. It is shown that in the presence of glucose, these polymers alter their swelling properties, either by ionization or by formation of glucose-mediated reversible crosslinks. Swelling pressures impinge on microdevice structures, leading either to a change in resonant frequency of a microcircuit, or valving action. Potential areas for future development and improvement are described. Finally, an asymmetric nano-microporous membrane, which may be integrated with the glucose-sensitive devices, is described. This membrane, formed using photolithography and block polymer assembly techniques, can be functionalized to enhance its biocompatibility and solute size selectivity. The work described here features the interplay of design considerations at the supramolecular, nano, and micro scales.
Bibliographical noteFunding Information:
This work was supported by NIH Grants EB003125 , DK075739 , HD040366 , and HD051366 , NSF Grant DMR-0605880 , US Army Grant DA/DAMD17-02-1-0722 , and a grant from the Spanish Ministry of Education, Culture, and Sports . We thank Prof. Marc A. Hillmyer and Drs. Anish Dhanarajan, Siddharthya Mujumdar, and Terry Davis for helpful discussions. Part of this work was carried out in the Institute of Technology Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the MRSEC, ERC and MRI programs. Other work was carried out in the Institute of Technology Nanofabrication Center, University of Minnesota, which receives partial support from NSF through the NNIN program.
- Block polymers
- Closed-loop insulin delivery
- Glucose sensing
- Microporous membrane
- Nanoporous membrane