The RaniPill is another syringe that you can swallow to deliver drugs to the bloodstream from the inside. It's triggered by an interesting and complex mechanism involving a chemical reaction that inflates a tiny polymer balloon to push the needle into the intestinal wall. Rani Therapeutics just completed a successful 20-person trial using a pill that shoots blanks. From IEEE Spectrum:
Working from the outside in, the RaniPill consists of a special coating that protects the pill from the stomach’s acidic juices. Then, as the pill is pushed into the intestines and pH levels rise to about 6.5, the coating dissolves to reveal a deflated biocompatible polymer balloon.
Upon exposure to the intestinal environment, a tiny pinch point made of sugar inside the balloon dissolves, causing two chemicals trapped on either side of the pinch point to mix and produce carbon dioxide. That gas inflates the balloon, and the pressure of the inflating balloon pushes a dissolvable microneedle filled with a drug of choice into the wall of the intestines. Human intestines lack sharp pain receptors, so the micro-shot is painless.
The intestinal wall does, however, have lots and lots of blood vessels, so the drug is quickly taken up into the bloodstream, according to the company’s animal studies. The needle itself dissolves...
Participants passed the remnants of the balloon within 1-4 days.
(Founder Mir) Imran calls the device a robot though it has no electrical parts and no metal. “Even though it has no brains and no electronics, it [works through] an interplay between material science and the chemistry of the body,” says Imran. “It performs a single mechanical function autonomously.”