Abstract: Techniques for deep tissue in vivo printing are described. Some implementations of the disclosure relate to a method that includes: obtaining a biopolymer mixture including prepolymer material and a crosslinking agent encapsulated in carrier particles; delivering the biopolymer mixture to a subcutaneous or deep tissue target location of a subject; and transmitting with a bioprinting device, via transcutaneous application, radiation to the subcutaneous or deep tissue target location, the radiation configured to cause the carrier particles to release at least some of the crosslinking agent, the released crosslinking agent configured to cause the prepolymer material to form into a gel or polymeric matrix.