Step 5: Inject EGaIn

Setup

The next step involves injecting the EGaIn into the hollow channels of the sensor. In order to do this, you will need 2 syringes with 27-gauge needles.

 

• Before getting started, make sure both syringes have their plungers depressed all the way.
• In one syringe, suck up 0.5 mL of EGaIn from a vial, then depress the plunger slightly to ensure there are no air bubbles inside the needle.
• Though not required, doing the injection under a magnifying scope will make it easier.

Injecting
	Approaching at a low angle, insert the needles into the rounded channel ends of the soft sensor. This low angle reduces the risk of puncturing the bottom of the sensor and creating a leak. You should be able to see the needle exit the rubber and enter the empty channel.
Slowly inject the EGaIn with one syringe while slowly pulling the plunger out of other syringe to evacuate the trapped air. If doing this simultaneously is too difficult, alternating the injection with the vacuum is fine. You should be able to see the EGaIn travel through the channels.  Before the EGaIn reaches the end, remove the vacuum needle. Inject a little excess so that some EGaIn leaks out the other side – and if there are any trapped air bubbles, keep injecting until all are removed. Make sure there are no air bubbles. Suck up any excess EGaIn that leaked and wipe/dab off the exit using a tissue wetted with IPA.

Bibliography

Mengüç et al. (2013) Soft Wearable Motion Sensing Suit for Lower Limb Biomechanics Measurements.

Mengüç et al. (To appear in 2014) Wearable Soft Sensing Suit for Human Gait Measurement.

Miserez et al. (2008) The Transition from Stiff to Compliant Materials in Squid Beaks.

Muth et al. (2014) Embedded 3D Printing of Strain Sensors within Highly Stretchable Elastomers.

Vogt, D. M., Park, Y. L., & Wood, R. J. (2013). Design and Characterization of a Soft Multi-Axis Force Sensor Using Embedded Microfluidic Channels.

Contributors

Yiğit Mengüç