Explosive Gel

The Explosive Gel is a gadget and occasional weapon. Batman could spray the gel on weak structures and detonate it at will. In combat, Batman could use the Quickfire Explosive Gel, in which he quickly sprayed the gel on the ground. When triggered, any enemy in the blast radius was knocked to the ground. The air powered weapon fires cartridges of highly destructive gelignite (a gelatinous form of explosive, used in the real world mostly for mining). Batman uses small amounts of the gel to minimize collateral damage and not kill bystanders (including himself).

Arkham Origins Incident
Batman had Explosive Gel even by the time of his second year of crime-fighting. In Multiplayer, any enemy caught in the blast radius of the Explosive Gel was instantly knocked out.

Arkham Origins Blackgate Incident
Batman utilized an "Explosive Gel Launcher" to fire gel onto surfaces that were not in direct reach.

Arkham Asylum Incident
Batman brought a supply of the Explosive Gel in the trunk of the Batmobile to Arkham Asylum, which he retrieved after The Joker began his takeover. It was the first weapon other than the Batarang that Batman used. Batman later used it to set a trap for Killer Croc and then in his fight against the Titan-enhanced Joker.

Arkham City Incident
Again, Batman utilized the Explosive Gel to explode everything that was in his way, from walls to thugs.

Arkham Knight Incident
The Explosive Gel returns in Batman: Arkham Knight, and it works similarly as the previous versions. In addition, quick firing will shoot a small glob of gel, which can temporarily make enemies disoriented and destroy weak wooden walls from a distance. However, the small glob has no effect on breakable brick walls. Every WayneTech Upgrades are only applied on the sprayed gel. Furthermore, sprayed gel is able to knock enemies unconscious should they approach the detonation radius during Predator Mode. Batman also uses this gadget to destroy the gun caches smuggled in by Penguin during the Gunrunner mission.

Gameplay
That gadget was used to break structures and could take down armed and unarmed thugs when it was used in collaboration with a structurally unsound wall. If a single spray of Explosive Gel was set off on a normal, structurally sound wall, the thug would only be knocked down and be made vulnerable to Ground Takedowns. Explosive Gel could be used to stun or take down thugs, confuse Titan-bosses, and destroy weak walls.

Batman: Arkham Asylum
Retrieved from the trunk of the Batmobile, upgrades to the Explosive Gel could be bought with XP through the WayneTech Upgrades Menu.

Explosive Gel Upgrades included:
 * Auto Proximity Detonation - Exploded when an enemy got near.
 * Multiple Frequency Detonator - Zoomed in on a specific gel patch to detonate only that specific patch.

Batman: Arkham City
The Explosive Gel worked in the same way as in Batman: Arkham Asylum, and all the upgrades that were available then were already in place at the start of the game. The Quickfire feature was introduced, which allowed Batman to apply it quickly on the ground. It was used more prominently to destroy the twelve Titan Containers around Arkham City.

Batman: Arkham Origins
The Explosive Gel worked the same way as it did in Batman: Arkham City.

Freeflow
In City and Origins, using the "Freeflow Gadgets" upgrade, the Explosive Gel had a much larger blast radius, which could, in turn, knock more enemies down. In Arkham Knight, using the Freeflow version of Explosive Gel made Batman shoot a ball of the gel to an enemy, but instead of the normal timer, it exploded instantly, and made all enemies in close proximity dizzy.

Tips

 * If the instant takedown upgrade is purchased in Knight, blowing up weak, wooden walls would result in an instant takedown, even when used against Minigunners, who aren't normally affected by the upgrade. This is extremely useful if the predator room doesn't have any traditional, strong breakable walls.
 * In City and Origins, if one managed to perform a Special Ground Multi Takedown after using special combo explosive gel, they could potentially knock out entire rooms of enemies in a few seconds. This is easier in Batman: Arkham Origins, if the upgrade that allows using two special moves in freeflow focus is purchased.

Trivia

 * While Batman tended to spray Explosive Gel patches in a crude bat shape, Robin sprayed his patches in his trademark "R" symbol, and Azrael sprayed his in a cross, the symbol of The Order of St. Dumas.
 * Originally, in Batman: Arkham Knight, Explosive Gel was only going to be used in context-sensitive areas and not chosen by the player on a gadget selection display.
 * In Arkham Knight, Quickfire Explosive Gel behaved very similarly to the Concussion Detonator from Batman: Arkham Origins, as it took a second to explode, and made the enemies dizzy.
 * The deployment gun could also be used for medical purposes, as Batman has stored the antidote to the Titan in Asylum, and took a sample of Ra's blood in City.
 * This would imply that Explosive Gel is stored in capsules in his utility belt until he needs to detonate an obstruction or needs to knock someone back.
 * The deployment gun appears to double as the remote detonator of the explosive gel, indicating the deployed gel contains an embedded microcharge that is detonated wirelessly, similar to real-world detonators.
 * The Explosive Gel is one of only five gadgets to appear in all Arkham games so far: the others are the Batarang, the Remote Control Batarang, the Line Launcher and the Batclaw.
 * In Arkham City 's museum, if the player tries to apply explosive gel to the ice in the torture room, Batman will refuse to do so, stating that it would be a very bad idea.