Starting in 2013, the project SmartSphincter aimed to realize prototype devices acting as artificial anal sphincter muscles, to treat patients with severe fecal incontinence. The device would replace the destroyed natural muscle function using low-voltage dielectric elastomer transducers (DET) acting as actuator and pressure sensors simultaneously. SmartSphincter was a nano-tera.ch initiative involving a consortium of university, clinical, and industrial partners spread across Switzerland, who are active in fields ranging from medicine and microelectronics to biomaterials science. The Swiss National Science Foundation and the Swiss Nanoscience Institute have financially supported the Artificial Muscle team.

Dielectric elastomer transducers (DET) exhibit a strain-stress behavior comparable to human tissues [1]. Their efficiency to convert electrical energy into mechanical one is outstanding, e.g. as artificial muscles they are established in soft robotics [2]. The use for medical implants, however, requires a reduction of the operation voltage by at least two orders of magnitude. Dielectric elastomer actuators based on elastomer layers several hundred nanometers thin have generated 6 % strain applying voltages as low as 12 V [3] and thus, have gained international interest within the community of electro-active elastomers [4]. However, thousands of nanostructures would have to be stacked realizing the force comparable to natural muscles. Therefore, the Bridge-Proof of Concept project, lead by Dr. Tino Töpper at the Biomaterials Science Center, will focus first on the sensing capability of the DETs, fabricated by organic molecular beam deposition [5,6]. Finally, these highly flexible DETs will serve as force-feedback sensor directly integrated on medical implants. These high-performance multi-layer sensors will remain operational even if one or the other layer fails due to breakdowns. With millisecond time response the functionality of artificial sphincters implants (MARS, Dr. N. Dhar, Wayne State University) for incontinence treatments will be significantly enhanced. Colleagues within the Department of Biomedical Engineering, under the supervision of Prof. G. Rauter, seek to implement the DET into sophisticated devices. Within the MIRACLE project the sensor arrays could become part of the endoscope that enables laser-based tissue cutting.

References:

1. Carpi, F. et al. Standards for dielectric elastomer transducers. Smart Materials and Structures  (2015)  24, 105025.
2. Madsen, F. B., Daugaard, A. E., Hvilsted, S. & Skov, A. L. The Current State of Silicone-Based Dielectric Elastomer Transducers. Macromolecular Rapid Communications  (2016)  37, 378-413.
3. Töpper, T. et al. Siloxane-based thin films for biomimetic low-voltage dielectric actuators. Sensors and Actuators A: Physical  (2015)  233, 32-41
4. Bar-Cohen, J. WW-EAP Newsletter  (2015)  17.
5. Töpper, T. et al. Time-resolved plasmonics used to on-line monitor metal-elastomer deposition for low-voltage dielectric elastomer transducers. Advanced Electronic Materials  (2017) 3, 8, 1700073
6. Töpper, T., Lörcher, S., Weiss, F. M. & Müller, B. Tailoring the mass distribution and functional group density of dimethylsiloxane-based films by thermal evaporation. APL Materials  (2016)  4, 056101.