Micro-capsules having an amorphous solid core

A droplet comprising:

• a metal alloy core in an amorphous solid state, the droplet having a temperature below a glass-transition temperature of the metal alloy core;
• and
• a shell fully enclosing the metal alloy core and including an inner metal layer, an outer metal-oxide layer, and an organic coating on an exterior surface of the outer metal-oxide layer, the shell configured to prevent or delay transition of the metal alloy core to a crystalline solid state when the droplet is exposed to a temperature above the glass-transition temperature,
• wherein a diameter of the droplet is between 2 and 160 microns.

A method of making a droplet, the method comprising:

• forming a metallic core of the droplet;
• forming a shell of the droplet around and fully enclosing the metallic core, the shell comprising an inner metal layer, an outer metal-oxide layer, and an organic coating on an exterior surface of the outer metal-oxide layer;
• and
• after forming the shell, transitioning the metallic core to an amorphous solid state to obtain an amorphous solid metallic core, wherein the shell is configured to prevent or delay transition of the amorphous solid metallic core to a crystalline solid state when the droplet is exposed to a temperature above a glass-transition temperature of the amorphous solid metallic core,
• wherein a diameter of the droplet is between 2 and 160 microns.