#  Step 2: Sensor Body 

 



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 ![sensor-body](/sites/g/files/omnuum4601/files/2024-11/sensor-body.jpg)

 

The sensor body is simply casted from silicone with embedded conductive interfaces at the ends.

Sort ![sensor-step1](/sites/g/files/omnuum4601/files/2024-11/sensor-step1.jpg)

 



Prepare the mold by inserting the **4 mm steel rod** and suspending the conductive rubber ends at both ends of the mold.

 ![sensor-step2](/sites/g/files/omnuum4601/files/2024-11/sensor-step2.jpg)

 



**Leave small gaps** between the end of the mold and the conductive rubber as shown.

 ![sensor-step3](/sites/g/files/omnuum4601/files/2024-11/sensor-step3.jpg)

 



Pour **25 g** each of **Part A** and **Part B** of the silicone rubber (PlatSil Gel-25) to a total of **50 g** into a mixing cup.

 ![sensor-step4](/sites/g/files/omnuum4601/files/2024-11/sensor-step4.jpg)

 



Stir the mixture. Periodically scrape the sides and bottom of the cup to ensure proper mixing. Please take into account the limited pot life of 5 minutes of the mixture.

*Vacuum degassing of the mixture is suggested but not required.*



 ![sensor-step5.pg_](/sites/g/files/omnuum4601/files/2024-11/sensor-step5.pg_.jpg)

 



Pour the silicone rubber mixture into the mold up to the brim.

Tap the bottom of the mold against a table repeatedly to remove any large air bubbles trapped inside.

Wait for the silicone rubber to completely cure.



 ![sensor-step6](/sites/g/files/omnuum4601/files/2024-11/sensor-step6.jpg)

 



Remove the **4 mm steel rod** by either twisting it out with a pair of pliers or securing the rod in a vise and twisting out the mold.

After the rod is removed, demold the sensor body from the mold using a small tool to pry out the sensor at the ends of the mold.



 ![sensor-step7](/sites/g/files/omnuum4601/files/2024-11/sensor-step7.jpg)

 



The completed sensor body

 ![sensor-step8](/sites/g/files/omnuum4601/files/2024-11/sensor-step8.jpg)

 



Cut the **silicone tubes** into 40 cm and 5 cm long sections and insert them into the sensor body as shown. Insert the end of the tubes only up until **half of the length of the conductive rubber**.

*Inserting the tube in too far might cover up the whole area of the conductive rubber in contact with the salt water, rendering the conductive rubber useless.*



 ![sensor-step9](/sites/g/files/omnuum4601/files/2024-11/sensor-step9.jpg)

 



Apply liberal amounts of **silicone adhesive** (Sil-Poxy) at the ends of the sensor body and let dry.

Any outer voids from the molding process can also be patched up at this point.



 ![sensor-step10](/sites/g/files/omnuum4601/files/2024-11/sensor-step10.jpg)

 



Insert the male 0.254" pins with the short side facing the sensor as shown. Glue the pins in place with silicone adhesive.

 ![sensor-step11](/sites/g/files/omnuum4601/files/2024-11/sensor-step11_0.jpg)

 



Once the adhesive has dried, the sensor is complete and ready to be charged with conductive fluid.





### Bibliography

Preechayasomboon et. al. [Multi-Modal Sensing and Actuation in Biomechanical Hydraulic and Pneumatic Systems.](/publications/multi-modal-sensing-and-actuation-biomechanical-hydraulic-and-pneumatic?admin_panel=1)

[Export Citation](/bibcite/export?content_filter%5B0%5D=1333742&format=bibtex)

### Contributors

Pornthep Preechayasomboon

Gaurav Mukherjee

Eric Rombokas