1. Fabrication and Design Considerations for Microfluidics-based Tactile Sensors for Prosthetic Hand Shehreen Dheda Faculty Mentor: Abraham P. Lee, PhD Graduate Mentor: Jeffrey S. Fisher Department of Biomedical Engineering, University of California, Irvine August 31, 2006 Inter-Micro/Nano Summer Undergraduate Research Experience (IM-SURE)

2. Outline: Biological mechanoreceptors of the human hand Our synthetic tactile sensor design Device manufacturing and characterization techniques and their outcomes Conclusions Acknowledgements

3. Biological Mechanoreceptors of the Human Hand Kandel, E. The Principles of Neural Sciences, 2000 (SA) Slowly Adapting (SA) afferents (RA) Rapidly Adapting (RA) afferents (SA)(SA)(RA)(RA)

4. Synthetic Tactile Sensor Design mimics Merkel cell-slowly adapting type 1 (SA-1) afferents mimics Meissner corpuscles-rapidly adapting (RA) afferents

5. Device Components Materials used are poly(dimethylsiloxane) (PDMS) and polyimide or glass. Reservoir shape molded into PDMS, and electrodes laid onto the polyimide/glass.

6. Filling Techniques Three different methods have been investigated: 1. Syringe 2. Pump 3. Channel Outgas Technique (COT) (Monahan et al, 2001) Monahan et al., Anal. Chem. 73: 3193-7 2001

7. Issues with Filling Techniques Air bubbles formed in reservoir with syringe and pump methods. For pump and COT method, sealing of PDMS where holes are made is necessary. COT needs modification to allow for selective filling.

8. Fluid Loss from the Devices Devices were filled using a syringe and sealed with uncured PDMS. They were kept at room temperature for a number of weeks and the loss of fluid out of the devices was tracked. Air bubbles on days 1, day 8 and day 16 respectively.

9. Mechanical Modeling of Sensor Stress within PDMS layer Fluid flow inside reservoir

10. Conclusions Improvements to existing filling techniques or more techniques need to be explored. Fluid loss is possible, so prevention is needed. Fluid flow from reservoir is linear to applied pressure. Other geometries and models should also be investigated.

11. Acknowledgements: A. P. Lee, PhD Jeffrey S. Fisher Wei-Yu (Tim) Tseng Undergraduate Research Opportunity Program, UROP National Science Foundation, NSF