Keyword:

Ultrasound Patch – thin polymer patch that is composed of small ultrasound transducers

• Ultrasound phased array – ultrasound patch that consists of transducers individually controlled by the computer
  • In sync can lead to ultrasound penetrating 14 cm deep into skin
  • Out of sync can be used to send ultrasound signals at various angles

Acoustic Impedance (Z) – physical property of tissue that measures the resistance an ultrasound beam encounters as it passes the tissue

Ultrasound Coupling Media – medium in which ultrasound wave is meant to be transmitted (gel, water, etc.) è this report uses Ca modified patch as the coupling medium instead of gel that is usually used in industry

Degumming – removing sericin from silk to only get silk fibroin (this process allows for the soft feel of silk)

• ultrasound coupling media is necessary for transmission efficiency maximization;

Ultrasound gel acts as medium instead of air that reduces transmission efficiency

Silk Fibroin: A Promising Tool for Wound Healing and Skin Regeneration (hindawi.com)

Goal: make patch between flexible transducer array and skin that maximizes high ultrasound transmission while providing adherence to skin

Problems of patches used:

1. Ultrasound gel
   1. Liquidity not suitable for portability
   2. Air bubbles create attenuation in ultrasound transmission
2. Ultrasound gel pad / Doppler ultrasound patch
   1. Not free-standing (requires extra stress to hold solid-like gel into place for measurements)
   2. Not applicable in bumpy skin

Important Procedures:

1. Find Most Appropriate silk:Ca2+ ratio

   1. Must be freestanding, flexible, and must form conformal contact with surface of skin (7:3 ratio)

   2. 8:2 ratio is too rigid (high stress with low stress => rigid and brittle)

   3. 6:4 ratio is too fluid (difficult to handle)

      

2. Water Content Percentage

   1. Water content determines the adhesiveness and conformity of adhesion to the skin

      

   2. Properties that affect cohesiveness:

      1. Metal chelation of Ca ions with random coil structure => high energy dissipation at interface
      2. Cross-linking of Ca ions and silk fibroin chains
      3. Note: too much water content can increase flowability and reduce cohesiveness

   3. “The ratio of peak intensities of the water molecule (3350 cm−1 ) to the chelate complex (3250 cm−1 ) increased when the silk patch was hydrated because the absorbed water molecules hindered the chelation of the Ca ions to the amino acid groups.” => ??