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| Strategy | Example | Advantage | Limitation | Application |
|
| Mold-based fabrication | Typical four-step method [15, 19–22] | Accurate, reusable, able to generate multicomponent microneedles, suitable for massive production, easy to operate | Inflexible, nonuniversal, unavoidable drug loss, confined by the molds, including time-consuming and technology-dependent steps | The most commonly used strategy, especially for massive production or industrial production |
| Modification via surface coating [3, 23] | Simple, controllable, accurate, protective of bioactive cargos, suitable for massive production, easy to operate | Inflexible, nonuniversal, confined by the molds, including time-consuming and technology-dependent steps | A strategy based on a typical four-step method, applicable to carrying bioactive cargos |
| Mold filling by imprinting [24, 25] | Accurate, protective of bioactive cargos | Inflexible, nonuniversal, unavoidable drug loss, confined by the molds, including time-consuming and technology-dependent steps, relying on extra equipment | A strategy based on a typical four-step method, applicable to carrying bioactive cargos |
| Mold filling by spin coating [26] | Accurate, protective of bioactive cargos | Inflexible, nonuniversal, confined by the molds, including time-consuming and technology-dependent steps, relying on extra equipment | A strategy based on a typical four-step method, applicable to carrying bioactive cargos |
| Mold filling by infiltrating or spraying [27] | Accurate, protective of bioactive cargos | Inflexible, nonuniversal, confined by the molds, including time-consuming and technology-dependent steps, relying on extra equipment | A strategy based on a typical four-step method, applicable to carrying bioactive cargos |
|
| Mold-free fabrication | Drawing lithography [16, 17] | Versatile, adjustable, economical, efficient, less-harmful, unrestricted by the molds, with simplified processes, with neglectable drug loss | Lacking accuracy, technology-dependent, only able to fabricate unilayer, cone-shaped microneedles | Applicable to carrying bioactive cargos |
| Droplet-born air blowing [18] | Versatile, adjustable, mild, less-harmful, unrestricted by the molds, with simplified processes, with neglectable drug loss | Lacking accuracy, technology-dependent, only able to fabricate unilayer, cone-shaped microneedles | Applicable to carrying bioactive cargos |
| Centrifugal lithography [28] | Versatile, adjustable, economical, mild, less-harmful, unrestricted by the molds, with simplified processes | Lacking accuracy, only able to fabricate unilayer, cone-shaped microneedles | Applicable to carrying bioactive cargos |
| 3D printing [29] | Accurate, unrestricted by the molds, suitable for elaborate synthesis, able to fabricate complicated patterns | Dependent on precision instrument, expensive, time-consuming | Suitable for fabricating microneedles with complicated structures |
| Microlens-integrated technique [30] | Inexpensive, mold-free, flexible, adjustable, scalable, automatic | Involving harmful steps, fastidious about microneedle materials | Potential in massive production or industrial production |
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