Can you design a single pack that can have a dual usage (as a cold and hot pack) Explain. Pls help

Popular and effective in treatments to ease pain and swelling from minor injuries, cold packs come in many different varieties. Some are sacks of gel that turn into ice packs in your freezer; others are packets designed to turn cold instantly with a simple squeeze, no refrigeration or freezing required. You can also make your own cold pack by wrapping some ice or a bag of frozen vegetables in a towel.

Heat can increase blood flow and help restore movement to injured tissue. Warmth can also reduce joint stiffness, pain, and muscle spasms. As with cold packs, heat packs have a role in easing pain from both acute and chronic injuries, such as sprains, strains, muscle spasms, whiplash, and arthritis. Doctors often suggest using cold packs for the first day or two, and then switching to heat if the symptoms persist or become more chronic.

Heat can increase blood flow and help restore movement to injured tissue. Warmth can also reduce joint stiffness, pain, and muscle spasms. As with cold packs, heat packs have a role in easing pain from both acute and chronic injuries, such as sprains, strains, muscle spasms, whiplash, and arthritis. Doctors often suggest using cold packs for the first day or two, and then switching to heat if the symptoms persist or become more chronic.In fact, for some folks, nothing soothes a sore back like a hot pack. In a study published in the journal Spine, investigators at the University of Medicine and Dentistry of New Jersey found that the continuous application of low-level heat eased low back pain better than two common over-the-counter painkillers.