User Guide for Single-threaded arrays

Required equipment to obtain recordings from Myomatrix arrays:

CAMBER provided: (see Figure 1)

• Myomatrix array 
• In-house fabricated ZIF-adapter board
• Plastic shim (from CAMBER) or paper shim (from user)
• Blunted 23g needle 

User provided:

• Headstage compatible with the Omnetics 36-pin connector  (part number NPD-36-VV-GS; A79026)
• SPI cable and data acquisition system. Refer to the CAMBER website > Getting Started > Tools and Equipment for a list of options. 

Figure 1: 

What should I do when the arrays arrive?

All Myomatrix arrays and accessories are experimental devices and purchased as-is. While the arrays are quite robust, below are some handling recommendations when removing them from the shipping package. 

• It is best to manipulate the arrays in the clear areas of polyimide on the ZIF interface end and not touch the electrode contacts. 
• Confirm you have received the correct array design(s). Each array has the array design code etched into the polyimide on the ZIF-interface end which can be visualized under a microscope or potentially with a phone camera. 
• Impedance test all devices within 30 days after delivery. Contact the CAMBER team at camber@emory.edu if impedances are in the +1MOhm range. General impedance testing instructions can be found HERE.

Critical things to do for a successful recording: 

• Don’t bend the array thread or roughly handle the electrode contacts. Avoid bending or kinking the array thread which can break the gold traces even if there is no visible breakage on the thread itself.
• Insert the ZIF interface into ZIF-adapter with a shim AND with the electrode contact side in direct contact with the PCB (see Step 3 of the Users Guide). 
• During injection, hold the insertion tail against the plastic needle hub so that the U-turn is flush against the blunted edge and does not move around during insertion (see Step 2 of the Users Guide)

General experimental protocol:

The best order of operations will depend on your specific experimental set-up. The steps below reflect a common approach to array insertion and EMG recording.

1. Pre-thread the array’s insertion tail into the blunted needle and sterilize these two components together.
2. Insert the array into the muscle target and secure the array thread to the subject with tape or surgical wrap. 
3. Connect the ZIF-interface end to the ZIF adapter and plug the adapter into the headstage. 
4. Connect the headstage to the data collection system. Run an impedance test prior to data collection to verify contact integrity and begin collecting EMG data.
5. Carefully remove the array from the subject. 

Detailed information for each protocol step listed above:

Sterilization:

Follow your institution’s regulations for sterilization of research devices for use in non-human primates or human subjects. The arrays can be sterilized in a typical high heat and steam autoclave or in an autoclave designed for sterilizing medical devices. Do not sterilize the ZIF-adapter board.

Example procedure:

1. The array thread is pre-loaded in the 23g blunted needle (see Figure 2). 
2. The array + needle are placed into an autoclavable pouch. 
3. Seal pouch and autoclave according to autoclave manufacturer’s instructions. 

Figure 2:

Insertion of the array:

After sterilization, insert the electrode end of the array into the target muscle as shown in Figure 3:

Insertion set-up:

1. Identify the muscle(s) where the insertion will take place. Considerations for insertion location include the putative location of the neuromuscular junctions of the target muscle or identification of blood vessels running beneath the insertion location.
2. Before proceeding further, wash your hands and put on a pair of examination gloves to maintain a clean environment.
3. Thoroughly wipe the skin surrounding the target area using either 70% EtOH or Isopropyl alcohol.
4. Cover the table with a surgical drape to create a clean field.
5. Carefully unpack the sterilized pouch and place the needle with the electrode on the sterile drape. 

Insert the Myomatrix probe:

1. Hold the insertion tail against the plastic hub (blue/green) base of the needle. It is important to ensure that the insertion tail is tightly held between the finger and the hub base. It is also important that the contact point between the electrode and the tip of the cannula is on the laser blunted surface. Figure 4 shows a real (4a) and graphical (4b) representation of how to hold the needle and insertion tail. 
2. Slowly insert the needle into the muscle at the desired entry point, using an angle of approximately 30-50 degrees. You may encounter some resistance before the needle pierces the skin or fascia. 
3. Continue slowly advancing the needle until the electrode contacts are through the fascia and positioned within the muscle. 
4. Release the tight hold of the tail against the plastic hub. Rotate the needle slightly in both clockwise and counterclockwise directions to ensure the tail is free from the cannula and slowly withdraw the cannula. 
5. While withdrawing the needle, be cautious not to pull out the tail or array parts. If the array adheres to the needle, attempting to rotate the needle a few more degrees may help.
6. After removing the needle, confirm that the electrode contacts remain below the skin. Ask the subject to contract the muscle to assess any pain or discomfort experienced during muscle contraction. 

 Connect the array to the ZIF adapter board (access video demo here):

1. Insert the shim into the ZIF clip and ensure it is pushed up against the end of the ZIF-clip. The shim is critical to ensure good electrical contact between the electrode and the adapter board.

NOTE: CAMBER typically ships the ZIF adapter with the shim set in the adapter (Figure 5) and/or places additional shims in the box with the needles or arrays. One can also use paper shims (~105g/m2 thick printer paper, cut to 5 mm x 18.5 mm). 

Figure 5:

Figure 6:

3. Close the ZIF clip and ensure that there is a snug fit by giving a soft tug with the forceps to the portion of the electrode outside of the ZIF clip (Figure 7). The electrode arrays are now electrically connected to the Omnetics adapter. If the shim is missing or incorrectly inserted the ZIF interface will pull right out of the ZIF clip.

Note - The order in which the shim and ZIF interface are inserted does not matter. What is essential for a reliable electrical connection between the array and the acquisition electronics is that the shim is fully inserted and the array contacts are flush against the adapter board.

Figure 7: 

1.  ZIF adapter board to the appropriate headstage and other data acquisition hardware. 
2. Figure 8 shows the Myomatrix array electrically connected to the headstage via the ZIF adapter. 
3. The headstage is then connected to whatever data collection system is being used. 
4. Run an impedance test to verify the integrity of the contacts after insertion. In our hands, impedances of ≤ 1 MOhm can yield a high resolution EMG signal. 
5. Data collection needs vary across experimental paradigms. Navigate to CAMBER website > Our Technology > Data analysis tools for a number of helpful resources. Of particular note is the link to the pinout maps for your Myomatrix device. 

Figure 8

Removing the array and (potentially) re-using the array:

1. Hold both the electrode and the insertion tail a few centimeters from where it enters the skin.
2. Firmly hold both the electrode and insertion tail portions of the device that remain outside the skin (~few cm from skin entry) and pull steadily until the full device is removed from the muscle and out of the skin. 
3. Disconnect the array from the adapter, which can be reused.
4. Re-use of the electrode array is not recommended for human subjects. Reach out to the CAMBER team to discuss potential options for re-use in certain animal protocols.