For applications that require a specific volume to be delivered or aspirated in the nanoliter / microliter / milliliter range, at a defined rate, Tritech Research offers the motorized MINJ-PD Digital Positive Displacement microINJECTOR™. Unlike most other microinjection controllers, this system does not require attachment to a gas cylinder, pump, or compressed air line. It works like an electronic syringe pump and is completely self-contained.

With the injection volume and speed set in advance, this motor-driven microinjector injects very small volumes of liquid with precision control via a foot switch, leaving both hands free for micromanipulation and focusing the microscope. In addition to fixed injection volumes, there is also a Manual Mode that allows the user to inject without knowing the volume in advance. In Manual Mode, the MINJ-PD displays a tally of the amount injected.

The MINJ-PD was originally designed for stem cell injection into blastocysts, and is now used for stem cell injections into human spinal cords. We're proud to say that (while For Research Use Only) it is currently the only FDA-listed device for injecting neural cells into the spinal cords of ALS patients and people with spinal cord injuries by the scientists at Neuralstem, Inc. and their collaborators worldwide. This injector is also used for micro-perfusion and delivery of drugs, neurotransmitters, and vectors to brain, retina, and cultured cells in neurobiology, for injecting insects in pathogen studies, and for many other applications. In 2017, we revised the hardware and firmware to support smoother, more precise delivery, easier loading of sterile syringes, and to add a Pressure Mode.

In addition to the original Positive-Displacement Mode, where the MINJ-PD syringe, tubing, etc. are filled with liquid for hydraulic action, a new Pressure Mode allows the MINJ-PD to be partially or completely air-filled for pneumatic injection control without the need of an external pressure source! In this mode, when you push the foot pedal, the syringe advances to create a positive pressure that makes things flow from the needle; when you release the pedal, the syringe returns to its neutral position to stop the injection flow. Inversely, the unit can be used to aspirate.

There are distinct advantages to Positive-Displacement Mode vs. Pressure Mode. In Positive-Displacement Mode, it is possible to set a specific delivery volume and delivery rate. Unfortunately, this is only practical for volumes over 1 µL because thermal expansion, elasticity, etc., become significant compared with volumes smaller than this. Pressure Mode can deliver volumes arbitrarily small, for example in the picoliter range, but the actual volume will be determined by the pressure, time, needle hole size, and viscosity of the the substance.

For stem cell injection, a special built-in Agitation Mode helps to prevent cells from clumping and settling on the wall of the needle between injections.

The MINJ-PD employs the same user-friendly microprocessor interface as the MINJ-D. It digitally synthesizes injecting / aspirating volume and speed, as well as agitating volume and speed, reproducibly. Using a simple "Menu" button, and Plus and Minus buttons, anyone can set the volumes and the speeds in seconds. Here are the key features and specifications of the Positive Displacement Digital microINJECTOR:

• Most compact and robust on the market
• 6" x 7" x 3" and weighs under 2 lbs.
• (15cm x 17cm x 7cm and weighs under 1 kg)
• Simple 3-button control
• Digital display with backlight for easy reading
• Microprocessor accuracy
• Foot pedal included for hands-free injection control
• Total syringe volume: 100uL (standard) (MINJ-PD-S100), or available 250 uL (MINJ-PD-S250), and 500uL (MINJ-PD-S500) options
• Programmable Injection volume: 0.01 - 50.0uL (with 100 uL syringe)
• Injection volume up to 400 uL with 500 uL syringe)
• Programmable Injection speed: 0.2 - 250.0s/uL
• Programmable Agitation volume: 0.1 - 25.0uL
• Programmable Agitation speed: 0.2 - 25.0s/uL
• Manual Injection Mode
• New "Pressure Mode"
• New syringe holder for quick change of pre-loaded and/orsterile syringes
• Optional Bi-directional Computer Interface for full automation
• Optional TTL trigger for automated injection

The output of the microINJECTOR needs to be coupled to something. For example, if you're using glass microcapillary needles, our MINJ-4 microINJECTOR™ Brass Straight-Arm Needle Holder will do the job cost-effectively. Please note that, for use with the MINJ-PD, a special version of all MINJ-4 variations will be supplied that uses a gas-tight swage fitting and terminates in a Luer/Slip fitting to attach conveniently to the MINJ-PD's syringe. The pictures below show the MINJ-4 variations with a quick-connect fitting that looks a bit different than what you will receive.