Ultrasensitive biomens sensors based on microcantilevers patterned with environmentally responsive hydrogels

J. Zachary Hilt, Amit K. Gupta, Rashid Bashir, Nicholas A. Peppas

Research output: Contribution to journalArticlepeer-review

135 Scopus citations


An innovative platform was developed for ultrasensitive microsensors based on microcantilevers patterned with crosslinked copolymeric hydrogels. A novel UV free-radical photolithography process was utilized to precisely align and pattern environmentally responsive hydrogels onto silicon microcantilevers, after microcantilevers were fabricated and released. Specifically, a crosslinked poly(methacrylic acid) network containing high amounts of poly(ethylene glycol) dimethacrylate was prepared and investigated. Hydrogels were patterned onto the silicon microcantilevers utilizing a mask aligner to allow for precise positioning. The silicon surface was modified with γ-methacryloxypropyl trimethoxysilane to gain covalent adhesion between the polymer and the silicon. The hydrogels sensed and responded to changes in environmental pH resulting in a variation in surface stress that deflected the microcantilever. The bending response of patterned cantilevers with a change in environmental pH was observed, showing the possibility to construct MEMS/BioMEMS sensors based on microcantilevers patterned with environmentally responsive hydrogels. An extraordinary maximum sensitivity of 1 nm/5 × 10-5 ΔpH was observed, demonstrating the ultrasensitivity of this microsensor platform.

Original languageEnglish
Pages (from-to)177-184
Number of pages8
JournalBiomedical Microdevices
Issue number3
StatePublished - Sep 2003

Bibliographical note

Funding Information:
The authors would like to acknowledge the support of the funding agencies. J.Z. Hilt was supported by NSF Integrative Graduate Education and Research Training (IGERT) Program in Therapeutic and Diagnostic Devices Grant DGE-99-72770. A.K. Gupta was supported by NSF Career grant ECS-9984189. The authors would also like to thank the staff of the micro-fabrication laboratories at Purdue University.


  • BioMEMS
  • Free-radical photopolymerization
  • Hydrogel
  • MEMS
  • Microcantilever
  • Micropatterning
  • Microsensor
  • pH sensor

ASJC Scopus subject areas

  • Biomedical Engineering
  • Molecular Biology


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